Verified Document

Transplant Medicine The Major Histocompatibility Complex MHC  Essay

Transplant Medicine The Major Histocompatibility Complex (MHC) contains over 128 functional genes. This is the densest part of the human genome and is responsible for most autoimmune diseases. This region also determines vaccine responsiveness, adverse drug reactions, disease progression and transplant rejection. The MHC genes are multigenic with a high degree of allelic polymorphism. There are over 7,500 different alleles and over 5,458 expressed MHC antigens currently known. (DeFranco, Locksley & Robertson, 2007). Genomic evolution and HLA screening have been extremely profitable to Transplant Medicine.

A brief analysis of MHC variability reveals two classes of antigens belonging to this complex; class I (A, B, and C) and II (DR, DQ, and DP). Both classes of molecules are expressed in a co-dominant fashion. These molecules are designed to recognize antigens that are foreign to the body and present them to the T cells. (Janeway, Travers & Walport, 2001)

The co-dominant mode of inheritance of MHC genes assures that each individual will have a distinct antigen on their cell surface. This forms the basis of graft rejection. Once a foreign antigen enters the human body, activation, proliferation and differentiation of lymphocytes into effector cells continues until the foreign antigen is eliminated, after which the immune system returns to its quiescent state and an immunologic memory is generated. (Janeway, Travers & Walport, 2001)

Tissue typing to match HLA antigens is an important step before transplantation. In general, the larger the number of matched MHC alleles between the donor and the recipient, greater are the chances of graft survival. However, routine HLA typing focuses only on HLA-A,...

(Janeway, Travers & Walport, 2001)
The extreme polymorphism of the MHC genes poses several challenges in recognizing the perfect donor, thus complicating HLA typing. The HLA nomenclature differs with the type of typing method used. Refinement of the serological typing of HLA antigens through the years has led to the identification of additional gene loci, which were previously thought to yield one antigen. For example, the B. 60 and B. 61 antigen were previously thought to be one antigen, the B. 40, based on their common ability to bind to a shared public epitope. Moreover, serology does not recognize heterogeneity of HLA antigens, as confirmed by DNA sequencing. Thus serological nomenclature is not representative of the true heterogeneity of the HLA system. HLA typing through this method may lead to a greater risk of graft rejection. (Badders, Houp, Sholander, Leffell & Zachary, 2010)

Further more, three different nomenclatures exist for defining HLA antigens. It is important to be able to appreciate the differences of each molecular typing nomenclature and to know which system is being used in the laboratory. Failure to do so may result in missed recognition of a donor specific antibody. (Badders et al., 2010)

Apart from the likelihood of graft rejection, recipients are faced with several challenges, such as prolonged waiting times and donor shortage, especially for sensitized individuals since they have additional immunological barriers. From 2000-2008, a total of 243,662 candidates were on the waiting list for kidney transplantation, with only 62,622 available donors in the United…

Sources used in this document:
REFERENCES:

Appel J.Z., Hartwig M.G., Cantu E., Palmer S.M., Reinsmoen N.L., Davis R.D. (2006). Role of flow cytometry to define unacceptable HLA antigens in lung transplant recipients with HLA-specific antibodies.Transplantation 81(7),1049-1057.

Badders J.L., Houp J.A., Sholander J.T., Leffell M.S., Zachary A.A. (2010). Considerations in interpreting solid phase antibody data. Hum Immunol 71(1),S18.

DeFranco, A.L., Locksley, R.M., & Robertson, M. (2007). Immunity: The immune response in infectious and inflammatory disease. (1st ed.). United Kingdom: Oxford University Press. Retrieved from http://www.biomedcentral.com/content/pdf/nsp-mhcpolymorphism.pdf

Janeway, C.J., Travers, P., & Walport, M. (2001).Immunobiology: The immune system in health and disease.. (5th ed.). New York: Garland Science. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK27163/
Reinsmoen, N., Lai, C., Vo, A., & Jordan, S.C. (2012, October 5). Evolving paradigms for desensitization in managing broadly hla sensitized transplant candidates. Retrieved from http://www.discoverymedicine.com/Nancy-Reinsmoen/2012/04/17/evolving-paradigms-for-desensitization-in-managing-broadly-hla-sensitized-transplant-candidates/
Cite this Document:
Copy Bibliography Citation

Related Documents

Ethics Organ Transplants for All
Words: 2139 Length: 7 Document Type: Research Paper

In theory, such evaluations could be useful, but as is, they are fairly useless. Plus, the validity and necessity of evaluations are up for debate themselves, besides the actual results from the evaluations being up for debate. Thus, the bioethical dilemma in those who abuse their bodies before and after receiving organ transplants lies not necessarily just with the recipients, but also with society, and with the medical field with

Ethics and Organ Transplants
Words: 837 Length: 2 Document Type: Essay

Ethical Considerations Behind Organ Transplants The idea of organ transplants has suffered several criticisms over the years from the civil society, to the various religious groups and even philosophers. It is challenging to have one perspective on the idea of transplants and apply it universally since not everyone will share the religious view, or the philosophical view. In the context of this memorandum, the utilitarian philosophy will be the baseline for

Organ Transplantation Has Been Regarded
Words: 1392 Length: 5 Document Type: Research Paper

In the U.S. For instance, Abuona (2003) indicated that the very first criterion is the donor's geographic location as compared to that of the recipient followed by the histocompatibility matching and blood group compatibility. The third criterion is a point system that each of the waiting-list patients accumulate in regard to the following variables; waiting time, medical urgency, as well as the age of the patient. This allocation technique

Organ Transplantation Denying Mrs. Burgone the Organ
Words: 1697 Length: 5 Document Type: Essay

Organ Transplantation Denying Mrs. Burgone the organ transplant could be ethically justified under certain conditions and circumstances. However, denying her organ transplantation surgery under these circumstances is not one of those instances and cannot be ethically justified. The decision is arbitrary and serves no purpose for any stakeholders in the outcome of the issue. Moreover, the ethical justification purported to be at the heart of the decision is logically flawed and

Organ Donating
Words: 1821 Length: 5 Document Type: Research Paper

Organ Donation Why Organ Donating is a Social Responsibility Life is a sentence. It begins with a capital letter, has something in between, and then a punctuation mark at the end. Organ donation allows part of our physical body to be of use to someone else for short time after we have passed. It is a beautiful gift to be able to make someone else's life a little longer. This gives them

Organ Donation in Contemporary UK
Words: 2693 Length: 8 Document Type: Research Proposal

2009). The susceptibility is highest is the first month of the transplantation and decreases afterwards. it, however, remains high even after 12 following. Susceptibility is highest among kidney recipients who are more likely to develop the infection 12 months after the transplantation. They have a lower mortality rate than liver transplant recipients. The study also reflected a trend in increasing antimicrobial resistance among these susceptible recipients. The E-coli strain

Sign Up for Unlimited Study Help

Our semester plans gives you unlimited, unrestricted access to our entire library of resources —writing tools, guides, example essays, tutorials, class notes, and more.

Get Started Now