I thought that they used an ample number of subjects and were very honest about the limitations of accuracy from some of the methods used in the study. Does anyone have any opinions on the design of the investigtation?
24 September 2008
News realse and article about Metabolic Syndrome
When I was looking into metabolic syndrome I wondered: how at risk are people to this disorder? I found a news release that directed me back to our topic of life style choices. It's a summary of an article that was published this summer about alcohol consumption (also posted).
23 September 2008
Prenatal Stress and postnatal outcome
I went to a presentation today by Chris Coe and he talked about prenatal stress and postnatal outcomes. The presentation covered a wide variety of topics ranging from psychological to immunological, so he was not able to go into much detail about any one topic. I do want to share with everyone the part about the immunology of the infant in a stressed mother.
Chris performed an experiment on pregnant monkeys. Once a day in the afternoon a loud noise would go off three times. He had three groups of monkeys: a control, ones stressed in early pregnancy, and ones stresses in late pregnancy. He said the stress was no more stressful than an average day for humans, and it would not alter the weight or the length of the pregnancy.
The results showed that stress anytime during a pregnancy can alter the immune response and overall health of the baby. When stressed the body naturally pulls iron out of the blood, and takes it to the muscles and organs. Stress deprives the baby of the necessary iron in the blood and can be born with an iron deficiency that can lead to anemia. Babies that are born with an iron deficiency do not receive enough iron from the mother after birth so they usually become anemic at about 6 months. The anemia affected the production of NK cells. The baby was born with a reduced number of NK cells and due to the anemia late in infancy the NK levels were reduced even more. This affected the infants response to pathogens.
This experiment also showed that cytokine levels were reduced in the infant. This shows that the adaptive response is altered. There was an increase in the TH-2 cells indicating that prenatal stress can lead to an increase in allergies and asthma in the child or adult. This was also demonstrated in another study were adults were asked about how their pregnancy went, if the mom was stressed or if they had a short gestation, normal, or long gestation and how that related to the health of the adult. In an interesting twist the adults that had a longer than average gestation usually had allergies or asthma as well as the adults with a short gestation.
This led me to wonder of the increase in asthma and allergies in children and adults is a result of the working culture we are in? Would we see a decrease in the number of children with allergies and asthma if the pregnant mother did not perform stressful activities?
Chris performed an experiment on pregnant monkeys. Once a day in the afternoon a loud noise would go off three times. He had three groups of monkeys: a control, ones stressed in early pregnancy, and ones stresses in late pregnancy. He said the stress was no more stressful than an average day for humans, and it would not alter the weight or the length of the pregnancy.
The results showed that stress anytime during a pregnancy can alter the immune response and overall health of the baby. When stressed the body naturally pulls iron out of the blood, and takes it to the muscles and organs. Stress deprives the baby of the necessary iron in the blood and can be born with an iron deficiency that can lead to anemia. Babies that are born with an iron deficiency do not receive enough iron from the mother after birth so they usually become anemic at about 6 months. The anemia affected the production of NK cells. The baby was born with a reduced number of NK cells and due to the anemia late in infancy the NK levels were reduced even more. This affected the infants response to pathogens.
This experiment also showed that cytokine levels were reduced in the infant. This shows that the adaptive response is altered. There was an increase in the TH-2 cells indicating that prenatal stress can lead to an increase in allergies and asthma in the child or adult. This was also demonstrated in another study were adults were asked about how their pregnancy went, if the mom was stressed or if they had a short gestation, normal, or long gestation and how that related to the health of the adult. In an interesting twist the adults that had a longer than average gestation usually had allergies or asthma as well as the adults with a short gestation.
This led me to wonder of the increase in asthma and allergies in children and adults is a result of the working culture we are in? Would we see a decrease in the number of children with allergies and asthma if the pregnant mother did not perform stressful activities?
Obesity and Diabetes II
The one issue we discussed yesterday in class that really caught my attention was the cultural differences and disposition to obesity and diabetes. It was the last research article that I enjoyed the most. The article compared the CRP levels (a possible marker for silent inflammation) of South Asian and European men and women. The article stated that the median CRP level in South Asian women was nearly double that in European women (1.35 vs 0.70mg=1, P .0.05). I found this interesting because we didn't cover much information on the subject in class, so I did some research of my own and found this article...
http://www.medscape.com/viewarticle/540922
A section of this article addresses an interesting topic we discussed in class regarding how normal BMI's may need to be altered to account for gender and cultural differences. Under the section titled "Asian Americans and Pacific Islanders" there is a table that highlights this. My only question to this would be how they accounted for the differences. What criteria did they consider?
I also liked how the article addressed possible reasons for why different cultures might have a higher incidence of diabetes. They talked about genetic differences, access to healthcare, and socioeconomic barriers to buying healthy foods and medication. The article is broken down into different sections by each race that was studied and it talks about the different initiatives that are underway to try and slow down the diabetes epidemic. If you have the time, it's a great article to read. Let me know what you think!
http://www.medscape.com/viewarticle/540922
A section of this article addresses an interesting topic we discussed in class regarding how normal BMI's may need to be altered to account for gender and cultural differences. Under the section titled "Asian Americans and Pacific Islanders" there is a table that highlights this. My only question to this would be how they accounted for the differences. What criteria did they consider?
I also liked how the article addressed possible reasons for why different cultures might have a higher incidence of diabetes. They talked about genetic differences, access to healthcare, and socioeconomic barriers to buying healthy foods and medication. The article is broken down into different sections by each race that was studied and it talks about the different initiatives that are underway to try and slow down the diabetes epidemic. If you have the time, it's a great article to read. Let me know what you think!
22 September 2008
Inflammation, Diabetes and Heart Disease
In the article "Profinflammatory cytokines are increased in type 2 diabetic women with cardiovascular disease", nondiabetic and diabetic women with and without cardiovascular disease are tested for plasma cytokine concentration (IL-1beta, IL-6, TNF-alpha). This article was particularly interesting to me because of how it described the snowball effect with diseases. During the last discussion, someone briefly mentioned how the inflammatory system had somewhat of a snowball effect (on the cellular level) where if one cytokine was present, more would be produced as an effect which would then signal for something else, etc, etc. In this article, it was suggested that inflammation effects many diseases/pathways at one time. For example, inflammation in type 2 diabetes can cause circulates cytokines which can aggravate atherosclerosis. Therefore hinting that if you have inflammation and type 2 diabetes, it would be likely for you to develop/encourage athersclerosis and heart problems. I think that this is the scary truth, but nonetheless, very fascinating. Note: Although this article does mention correlations, it states that there has been no studies that have grasped the correlation of cytokine concentrations in women with both cardiovascular disease and diabetes
In addition to disease relationships, this article reported some facts. Here are a few that I found pertinent.
- 17 million people in U.S. have diabetes. 95% of those people have type 2 diabetes.
- in 2000, CVD was #1 cause of death among women in U.S. (American Heart Association)
In addition to disease relationships, this article reported some facts. Here are a few that I found pertinent.
- 17 million people in U.S. have diabetes. 95% of those people have type 2 diabetes.
- in 2000, CVD was #1 cause of death among women in U.S. (American Heart Association)
19 September 2008
During our first discussion about Type II Diabetes and its relation to inflammation we spent quite a bit of time talking about diet. As this subject continued to come up I was constantly reminded that the issue was not entirely about subjective decision making but also had many social implicatiaions. One factiod that stuck in my mind was that inflammatory factors stay elevated for up to four hours after eating fast food. Well I found this article that specifically focuses of the inflammatory effects of the "Western Diet" and wanted to share it and wanted to know what you all thought about the increasing importance of AGEs and AGE receptors.
Cardiac inflammation associated with a Western diet is mediated via activation of RAGE by AGEs: http://ajpendo.physiology.org/cgi/content/short/295/2/E323
17 September 2008
I came across a recent article in science which described how certain type of cells within the thymus that express autoimmune regulators (AIRES) that act as safety net for eliminating autoreactive immune cells.
Science 8 August 2008:Vol. 321. no. 5890, pp. 776 - 777DOI: 10.1126/science.1162966
Prev Table of Contents Next
Perspectives
IMMUNOLOGY:A Breath of Aire for the PeripheryBruno Kyewski*
The term "self-tolerance" encompasses all mechanisms that protect the body against attack by its own immune system. The adaptive arm of the immune system generates immune cells that express antigen-specific receptors by a random mechanism that requires quality control--selecting a "personalized" repertoire of receptors directed against foreign but not self-antigens (1). Central and peripheral tolerance to self are distinguished according to the site where tolerance is imposed (2). Central tolerance for T lymphocytes occurs in the thymus, where their primary antigen receptor repertoire is generated. Here, developing T cells that recognize and react to self-antigens are eliminated or diverted into T regulatory cells that suppress activation of the immune system and prevent self-reactivity. Although the thymus displays a vast array of self-antigens, including those whose expression is otherwise restricted to specific tissues, this collection is nevertheless incomplete. On page 843 of this issue, Gardner et al. (3) report how peripheral lymphoid tissues act as a safety net, preventing T cells specific for antigens not presented in the thymus from escaping elimination.
Medullary thymic epithelial cells, a particular thymic stromal cell type, express a diverse set of genes that are otherwise restricted to certain tissues and/or stages of development (4). This so-called promiscuous gene expression in the thymus is partly regulated by a transcriptional regulator called the Autoimmune regulator (Aire). Mice deficient in Aire develop a multi-organ autoimmune syndrome, similar to that of humans with functional mutations in the Aire gene (5).
Aire is highly expressed in thymic medullary epithelial cells. However, the functionally relevant expression of Aire in cells of peripheral lymphoid organs has been controversial (5-9). Gardner et al. now identify cells in peripheral lymph nodes, spleen, and Peyer's patches (lymphoid structures of the gut), that express Aire and mediate deletion of auto-reactive T cells. The authors genetically engineered mice in which the promoter of the Aire gene drives expression of a fusion protein composed of green fluorescent protein and islet-specific glucose-6-phosphatase related protein (Igrp), an antigen specific to the pancreas. Of the medullary thymic epithelial cells and peripheral cells that expressed the reporter protein, 85% and 25% expressed endogenous Aire, respectively. Most of these peripheral cells, called extrathymic Aire-expressing cells, were stromal-type epithelial cells, located at the interface between T and B cell areas in peripheral lymphoid tissues. These cells also expressed receptors characteristic of antigen-presenting cells, but differed in several markers from the medullary epithelial cells in the thymus. Surprisingly, some of these extrathymic Aire-expressing cells were highly mobile within the lymph node microenvironment, and at the same time were able to delete T cells specific for the reporter protein.
Complementary tolerance. The transcriptional regulator Aire controls the expression of complementary pools of self-antigens in the thymus and peripheral lymphoid tissues that sequentially imprint central and peripheral T cell tolerance, respectively.
CREDIT: C.BICKEL/SCIENCEPerhaps the most intriguing result of this study relates to the target genes controlled by Aire in the thymus versus the periphery. The number of genes in the latter is about one-tenth of that in the thymus, and their degree of Aire-dependent regulation is less pronounced. Moreover, although there is little overlap between the gene pools, both are clearly enriched in genes encoding for tissue-restricted self-antigens (see the figure). The distinct composition of both gene pools favors a role for peripheral tolerance that is complementary to tolerance developed in the thymus. A recent study by Lee et al. also identified a fraction of nonhematopoietic cells in mesenteric lymph nodes that express Aire and certain tissue-restricted self-antigens, and mediates peripheral T cell deletion (9). However, these cells were less rigorously enriched, and differed phenotypically, compared to those identified by Gardner et al. Moreover, the data of Lee et al. are more in line with the concept that peripheral tolerance serves as a backup for central tolerance rather than being complementary.
The study by Gardner et al. still leaves some important questions that need to be answered before a definitive role can be assigned to Aire in peripheral tolerance. Why do only 25% of peripheral cells in the transgenic mice that express the fluorescent reporter protein also express endogenous Aire? Is it due to ectopic expression of the reporter construct in otherwise Aire-negative cells? Is endogenous expression of Aire too low to be detected, or is expression of Aire and the reporter protein not synchronized? The relatively low concordance between the reporter and endogenous Aire expression may also contribute to the apparently relatively low degree of gene expression induced by Aire in the peripheral cells, which for most genes is less than twofold compared to the background expression in Aire-deficient mice.
Although tolerance induction is thought to be exquisitely sensitive to low numbers of self-antigens that are presented to T cells in the context of the major histocompatibility complex, it will be essential to show that the low expression level of endogenous tissue-restricted self-antigens in peripheral Aire-expressing cells are "tolerogenic." After all, at first glance, the autoimmune phenotype of Aire-deficient mice was fully reproduced by transplanting Aire-deficient thymic stromal cells (with no functional evidence for Aire in extrathymic sites) (5). Given the different composition of self-antigens displayed in peripheral cells, the autoimmune phenotype caused by lack of Aire in the periphery may have been subtle and previously overlooked. Notwithstanding these caveats, the study by Gardner et al. raises intriguing questions about the role and function of Aire and the nature of the peripheral cells that express this factor (10).
The emergence of the extrathymic Aire-expressing cells in vertebrates is interesting, given that organized secondary lymphoid organs evolved much later than the thymus (11). Aire is a single-copy gene with orthologs in mammals, birds, and fish whose structure has been conserved in vertebrates over more than 400 million years (12). No ancestral Aire genes have been reported in invertebrates. This suggests that Aire and its role in tolerance were acquired early during vertebrate evolution, most likely concurrent with the emergence of the adaptive immune system. One question is whether Aire's only role is to ensure central tolerance, or whether it has been coopted for other functions. The study by Gardner et al. now presents a strong argument in favor of the latter--Aire also seems to contribute to establishing peripheral tolerance.
Science 8 August 2008:Vol. 321. no. 5890, pp. 776 - 777DOI: 10.1126/science.1162966
Prev Table of Contents Next
Perspectives
IMMUNOLOGY:A Breath of Aire for the PeripheryBruno Kyewski*
The term "self-tolerance" encompasses all mechanisms that protect the body against attack by its own immune system. The adaptive arm of the immune system generates immune cells that express antigen-specific receptors by a random mechanism that requires quality control--selecting a "personalized" repertoire of receptors directed against foreign but not self-antigens (1). Central and peripheral tolerance to self are distinguished according to the site where tolerance is imposed (2). Central tolerance for T lymphocytes occurs in the thymus, where their primary antigen receptor repertoire is generated. Here, developing T cells that recognize and react to self-antigens are eliminated or diverted into T regulatory cells that suppress activation of the immune system and prevent self-reactivity. Although the thymus displays a vast array of self-antigens, including those whose expression is otherwise restricted to specific tissues, this collection is nevertheless incomplete. On page 843 of this issue, Gardner et al. (3) report how peripheral lymphoid tissues act as a safety net, preventing T cells specific for antigens not presented in the thymus from escaping elimination.
Medullary thymic epithelial cells, a particular thymic stromal cell type, express a diverse set of genes that are otherwise restricted to certain tissues and/or stages of development (4). This so-called promiscuous gene expression in the thymus is partly regulated by a transcriptional regulator called the Autoimmune regulator (Aire). Mice deficient in Aire develop a multi-organ autoimmune syndrome, similar to that of humans with functional mutations in the Aire gene (5).
Aire is highly expressed in thymic medullary epithelial cells. However, the functionally relevant expression of Aire in cells of peripheral lymphoid organs has been controversial (5-9). Gardner et al. now identify cells in peripheral lymph nodes, spleen, and Peyer's patches (lymphoid structures of the gut), that express Aire and mediate deletion of auto-reactive T cells. The authors genetically engineered mice in which the promoter of the Aire gene drives expression of a fusion protein composed of green fluorescent protein and islet-specific glucose-6-phosphatase related protein (Igrp), an antigen specific to the pancreas. Of the medullary thymic epithelial cells and peripheral cells that expressed the reporter protein, 85% and 25% expressed endogenous Aire, respectively. Most of these peripheral cells, called extrathymic Aire-expressing cells, were stromal-type epithelial cells, located at the interface between T and B cell areas in peripheral lymphoid tissues. These cells also expressed receptors characteristic of antigen-presenting cells, but differed in several markers from the medullary epithelial cells in the thymus. Surprisingly, some of these extrathymic Aire-expressing cells were highly mobile within the lymph node microenvironment, and at the same time were able to delete T cells specific for the reporter protein.
Complementary tolerance. The transcriptional regulator Aire controls the expression of complementary pools of self-antigens in the thymus and peripheral lymphoid tissues that sequentially imprint central and peripheral T cell tolerance, respectively.
CREDIT: C.BICKEL/SCIENCEPerhaps the most intriguing result of this study relates to the target genes controlled by Aire in the thymus versus the periphery. The number of genes in the latter is about one-tenth of that in the thymus, and their degree of Aire-dependent regulation is less pronounced. Moreover, although there is little overlap between the gene pools, both are clearly enriched in genes encoding for tissue-restricted self-antigens (see the figure). The distinct composition of both gene pools favors a role for peripheral tolerance that is complementary to tolerance developed in the thymus. A recent study by Lee et al. also identified a fraction of nonhematopoietic cells in mesenteric lymph nodes that express Aire and certain tissue-restricted self-antigens, and mediates peripheral T cell deletion (9). However, these cells were less rigorously enriched, and differed phenotypically, compared to those identified by Gardner et al. Moreover, the data of Lee et al. are more in line with the concept that peripheral tolerance serves as a backup for central tolerance rather than being complementary.
The study by Gardner et al. still leaves some important questions that need to be answered before a definitive role can be assigned to Aire in peripheral tolerance. Why do only 25% of peripheral cells in the transgenic mice that express the fluorescent reporter protein also express endogenous Aire? Is it due to ectopic expression of the reporter construct in otherwise Aire-negative cells? Is endogenous expression of Aire too low to be detected, or is expression of Aire and the reporter protein not synchronized? The relatively low concordance between the reporter and endogenous Aire expression may also contribute to the apparently relatively low degree of gene expression induced by Aire in the peripheral cells, which for most genes is less than twofold compared to the background expression in Aire-deficient mice.
Although tolerance induction is thought to be exquisitely sensitive to low numbers of self-antigens that are presented to T cells in the context of the major histocompatibility complex, it will be essential to show that the low expression level of endogenous tissue-restricted self-antigens in peripheral Aire-expressing cells are "tolerogenic." After all, at first glance, the autoimmune phenotype of Aire-deficient mice was fully reproduced by transplanting Aire-deficient thymic stromal cells (with no functional evidence for Aire in extrathymic sites) (5). Given the different composition of self-antigens displayed in peripheral cells, the autoimmune phenotype caused by lack of Aire in the periphery may have been subtle and previously overlooked. Notwithstanding these caveats, the study by Gardner et al. raises intriguing questions about the role and function of Aire and the nature of the peripheral cells that express this factor (10).
The emergence of the extrathymic Aire-expressing cells in vertebrates is interesting, given that organized secondary lymphoid organs evolved much later than the thymus (11). Aire is a single-copy gene with orthologs in mammals, birds, and fish whose structure has been conserved in vertebrates over more than 400 million years (12). No ancestral Aire genes have been reported in invertebrates. This suggests that Aire and its role in tolerance were acquired early during vertebrate evolution, most likely concurrent with the emergence of the adaptive immune system. One question is whether Aire's only role is to ensure central tolerance, or whether it has been coopted for other functions. The study by Gardner et al. now presents a strong argument in favor of the latter--Aire also seems to contribute to establishing peripheral tolerance.
tobacco
it was interesting that tobacco plant is used for making antibodies. IS this because tobacco is one of the plants which can be regenerated froma single cell. Can potatoe plants be used for this purpose. i have heard taht they can also be regenerated from a single cell
14 September 2008
Obesity and Diabetes
I just wanted to give a brief overview of how obesity, inflammation, and type 2 diabetes are related for this week’s class. After reading a few research articles on the subjects I found that obesity essentially causes chronic inflammation. This has been verified in studies by high plasma concentrations of molecules such as tumor necrosis factor, interleukin-6, and C-reactive protein. In fact, it is the adipose tissue itself that acts like an organ and secretes hormones and cytokines that can cause this inflammation. The resulting chronic inflammation has been found to be the cause of insulin resistance and type 2 diabetes. Since this is a relatively new subject in science, the exact mechanisms and causes are not fully understood and are currently being investigated.
http://www.idf.org/home/index.cfm?unode=c659495d-7467-45c0-8a19-5b3d8ea3d172
I came across this article while searching for more information on diabetes and obesity. The article comes from the International Diabetes Foundation. Some of the statistics in it are extremely alarming. For example, the article states that diabetes and other diseases that result from obesity are responsible for more deaths annually worldwide than AIDS. It also explained that obesity and diabetes caused by obesity are worldwide epidemics. I may be alone in this, but I always envisioned obesity and resulting health problems to be more prominent in the US and parts of Europe. However, the article states that it’s becoming a major problem in “low to moderate income countries” like South Africa, Egypt, and Mexico. The article really conveys a sense of urgency and calls for a worldwide effort to change diets and lifestyles. I’m just curious to hear everyone’s views on the matter. What do you think?
Finally, I was wondering if anybody was able to come across any information on how to effectively screen for this “silent inflammation.” I know blood tests can reveal markers like C-reactive protein but as the previous post states, C-reactive proteins do not indicate inflammation exclusively.
http://www.idf.org/home/index.cfm?unode=c659495d-7467-45c0-8a19-5b3d8ea3d172
I came across this article while searching for more information on diabetes and obesity. The article comes from the International Diabetes Foundation. Some of the statistics in it are extremely alarming. For example, the article states that diabetes and other diseases that result from obesity are responsible for more deaths annually worldwide than AIDS. It also explained that obesity and diabetes caused by obesity are worldwide epidemics. I may be alone in this, but I always envisioned obesity and resulting health problems to be more prominent in the US and parts of Europe. However, the article states that it’s becoming a major problem in “low to moderate income countries” like South Africa, Egypt, and Mexico. The article really conveys a sense of urgency and calls for a worldwide effort to change diets and lifestyles. I’m just curious to hear everyone’s views on the matter. What do you think?
Finally, I was wondering if anybody was able to come across any information on how to effectively screen for this “silent inflammation.” I know blood tests can reveal markers like C-reactive protein but as the previous post states, C-reactive proteins do not indicate inflammation exclusively.
Obesity and Inflammation
Hello everyone!!
I have read the obesity/diabetes articles and I want to share some ideas from the articles that I found interesting (but you don't have to).
In the articles "Obesity and the Flu", "Visceral Fat Pronounced Guilty of Systemic Inflammation" and "In Diabetes, a Complex of Causes", visceral fat/skeleton was labled as an endocrine organ. I recently heard that fat had a metabolic function, but I did not know that it was therefore classified as an organ. This is a relatively recent discovery in the scientific world, and will provide new hypotheses for years to come.
In our last class, on Monday, September 8th, we discussed a short article titled, "The Inflammation Age" from Better Nutrition. At the end of this article, it suggested that a simple blood plasma test that investigated levels of CRP (C-reactive protein) was the best tool to understand your risks of inflammation. However, Zoe pointed out to the class that the method may be skewed. Why do many of the articles given to us about obesity/diabetes and the relationship with diabetes suggests that levels of CRP can be an efficient way of detecting inflammation? After further investigation, I gathered that abnormal CRP levels can be the consequence of different things, such as viral infections and liver failure. Therefore, this test proves to not be very specific. As Zoe mentioned, this test may not accurately detect what we are looking for.
In addition to the above, I would like to pose a question for the future. What do you think is the most efficient way to treat obesity and diabetes? There have been multiple medications that have been tested and used. Exercise and diet have been tried countless times. Different surgical methods have been discovered and performed. I think that since all of the treatments have various routes, diverse side effects and risks, and distinct goals, it is very hard to compare them. Maybe each patient has a "best" treatment for themselves and their condition.
I have read the obesity/diabetes articles and I want to share some ideas from the articles that I found interesting (but you don't have to).
In the articles "Obesity and the Flu", "Visceral Fat Pronounced Guilty of Systemic Inflammation" and "In Diabetes, a Complex of Causes", visceral fat/skeleton was labled as an endocrine organ. I recently heard that fat had a metabolic function, but I did not know that it was therefore classified as an organ. This is a relatively recent discovery in the scientific world, and will provide new hypotheses for years to come.
In our last class, on Monday, September 8th, we discussed a short article titled, "The Inflammation Age" from Better Nutrition. At the end of this article, it suggested that a simple blood plasma test that investigated levels of CRP (C-reactive protein) was the best tool to understand your risks of inflammation. However, Zoe pointed out to the class that the method may be skewed. Why do many of the articles given to us about obesity/diabetes and the relationship with diabetes suggests that levels of CRP can be an efficient way of detecting inflammation? After further investigation, I gathered that abnormal CRP levels can be the consequence of different things, such as viral infections and liver failure. Therefore, this test proves to not be very specific. As Zoe mentioned, this test may not accurately detect what we are looking for.
In addition to the above, I would like to pose a question for the future. What do you think is the most efficient way to treat obesity and diabetes? There have been multiple medications that have been tested and used. Exercise and diet have been tried countless times. Different surgical methods have been discovered and performed. I think that since all of the treatments have various routes, diverse side effects and risks, and distinct goals, it is very hard to compare them. Maybe each patient has a "best" treatment for themselves and their condition.
10 September 2008
A Clinical Application for Immunology
In class this Tuesday, we spoke briefly about immunological assays and how they have become widely used in the clinical world. Because I recently worked in a clinical lab using these techniques, I thought I would share the large part that they actually played.
Before coming to UCD, I worked for a clinical lab that concentrated on organ transplantation. When most people think of immunology and organ transplants, we think of anti-rejection drugs and antibody cross-matching (such as blood typing). As a part of the Infectious Disease department, our job was to make sure that organ donors did not have any infectious diseases (such as HIV and Hepatitis). It may not be inherently obvious as with cross-matching, but immunology plays an important role in this process. To do this, we used a process called Enzyme Immunoassays, or EIAs. This process is basically an antibody-antigen reaction.
When testing for these infectious diseases, the easiest, fastest, and most generally reliable method is to look in the blood for the antibody. A manufactured protein, similar in structure to the disease antigen is affixed to the bottom of a plate. When the serum or plasma of a patient is added, after a period of incubation, any antibody present in the patient’s blood will become bound to the antigen. Everything else is washed away, leaving only the antibody-antigen complex. This complex can be conjugated to a color development reagent, allowing visible representation of the amount of antibody in the blood.
This method of testing is very fast and efficient. If needed to be done quickly, all of the tests required by the FDA for whole organ transplantation can be done within six hours. (This is very handy for someone on a list waiting for an organ.) It is also possible to perform this kind of test on multiple patients at one time, as they can be done on 96-well plates. Unfortunately, some down-sides become apparent with this method of testing. For one, it relies on antibodies made to viruses, instead of the actual virus. There is a period time called the “window period” in which the virus is in the body, but our immune system has not been able to make a detectable amount of antibody. It is rare, but possible that an organ donor could have died without knowing they had recently contracted a disease, and their blood was drawn for testing during this window period. A solution for this is a method of Nucleic Acid Testing (NAT) called Transcription Mediated Amplification which detects the genetic material of viruses using a technique similar to PCR. This can detect the presence of a virus much earlier than EIA testing, but is not available for all infectious diseases.
Another drawback to using EIAs to detect diseases is the phenomenon of cross-reaction, which we also discussed in class. As you might imagine, there are proteins that are similar in structure to antibodies. Cross reactivity is one of the main causes of false positive results in EIAs. For example, if a blood sample is hemolyzed (the red blood cells have lysed), the protein fragments released could become bound to the antigen and the patient would appear to be reactive. There is not much that can be done about this, especially if a person has a medical condition that causes them to produce proteins similar to the antigen being tested for. As more nucleic acid testing becomes available, it will be easier to detect diseases, and fewer organs will have to be discarded because of false positive results.
If anyone happens to comment on this or have a question, I'll be out of town for the rest of the month :)
Before coming to UCD, I worked for a clinical lab that concentrated on organ transplantation. When most people think of immunology and organ transplants, we think of anti-rejection drugs and antibody cross-matching (such as blood typing). As a part of the Infectious Disease department, our job was to make sure that organ donors did not have any infectious diseases (such as HIV and Hepatitis). It may not be inherently obvious as with cross-matching, but immunology plays an important role in this process. To do this, we used a process called Enzyme Immunoassays, or EIAs. This process is basically an antibody-antigen reaction.
When testing for these infectious diseases, the easiest, fastest, and most generally reliable method is to look in the blood for the antibody. A manufactured protein, similar in structure to the disease antigen is affixed to the bottom of a plate. When the serum or plasma of a patient is added, after a period of incubation, any antibody present in the patient’s blood will become bound to the antigen. Everything else is washed away, leaving only the antibody-antigen complex. This complex can be conjugated to a color development reagent, allowing visible representation of the amount of antibody in the blood.
This method of testing is very fast and efficient. If needed to be done quickly, all of the tests required by the FDA for whole organ transplantation can be done within six hours. (This is very handy for someone on a list waiting for an organ.) It is also possible to perform this kind of test on multiple patients at one time, as they can be done on 96-well plates. Unfortunately, some down-sides become apparent with this method of testing. For one, it relies on antibodies made to viruses, instead of the actual virus. There is a period time called the “window period” in which the virus is in the body, but our immune system has not been able to make a detectable amount of antibody. It is rare, but possible that an organ donor could have died without knowing they had recently contracted a disease, and their blood was drawn for testing during this window period. A solution for this is a method of Nucleic Acid Testing (NAT) called Transcription Mediated Amplification which detects the genetic material of viruses using a technique similar to PCR. This can detect the presence of a virus much earlier than EIA testing, but is not available for all infectious diseases.
Another drawback to using EIAs to detect diseases is the phenomenon of cross-reaction, which we also discussed in class. As you might imagine, there are proteins that are similar in structure to antibodies. Cross reactivity is one of the main causes of false positive results in EIAs. For example, if a blood sample is hemolyzed (the red blood cells have lysed), the protein fragments released could become bound to the antigen and the patient would appear to be reactive. There is not much that can be done about this, especially if a person has a medical condition that causes them to produce proteins similar to the antigen being tested for. As more nucleic acid testing becomes available, it will be easier to detect diseases, and fewer organs will have to be discarded because of false positive results.
If anyone happens to comment on this or have a question, I'll be out of town for the rest of the month :)
Subscribe to:
Posts (Atom)