Clinical immunology - Essay Example

Clinical Immunology Organ transplantation has become a therapeutic modality to treat patients with end-stage disease. However, inadequate precaution,illegal organ trade, and higher presence of diseases such as HIV, hepatitis, and malaria present greater health safety dangers to both organ donors and recipients in developing countries (Wikipedia, 2006). In recent years although 1-year survival after organ transplantation has improved markedly over the last 15 years, there has been little success in reversing the decline in long-term graft and patient survival that is seen in recipients of any organ transplant, in whom the prevalence of morbidities such as systemic hypertension, diabetes mellitus, renal insufficiency, and malignancy remain high as compared with the general population.

The barriers to short and long-term success of transplant procedures are predominantly the result of incompatibility between donor and recipient, acute and chronic rejection, and complications of long-term pharmacologic immune suppression. This is the reason why clinicians need to consider several factors prior to transplantation. Examples of conditions to be studied include, but are not limited to: 1. Pre-existing immunologic barriers (such as anti-HLA antibodies or ABO incompatibility) to successful transplantation.2. Chronic, progressive allograft destruction (e.g., allograft nephropathy, obliterative bronchiolitis) after organ transplantation.3. Immunomodulatory interventions targeting innate immunity and/or autoimmunity in transplant donors or recipients. 4. New, less toxic immunosuppressive agents or regimens, or innovative approaches to develop donor-specific tolerance.5. Prevention or treatment of post-transplant lymphoproliferative disorder and malignancy.6. Susceptibility to and prevention of the adverse consequences (e.g., nephropathy, systemic hypertension, diabetes mellitus, malignancy) of current post-transplant immunosuppressive regimens (Department of Health and Human Services, 2003).

In many cases of transplantation the histocompatibility barrier between recipient and donor remains a problem in that it will activate immune responses leading to graft rejection. Because HLA plays such a dominant role in transplant immunity, pre-transplant histocompatibility testing seems important for organ transplantation. In order to appreciate the role of Human Leukocyte Antigen (HLA) in transplantation, we must first consider the structural and functional aspects of HLA molecules. HLA antigens are controlled by a series of highly polymorphic genes on the short arm of chromosome 6, referred to as the human MHC.

These genes have been classified into major categories. HLA-A, HLA-B and HLA-C encode for Class I molecules consisting of a 45kD glycopeptide chain complexed to a 12kD 2-microglobulin chain encoded by a nonpolymorphic gene on chromosome 15. The genes in the HLA-DR, HLA-DQ and HLA-DP regions encode for Class II molecules consisting of a ~30kD -chain and a ~28kD -chain. These HLA class I and class II alloantigens can induce transplant immunity at both humoral (antibody) and cellular (T lymphocyte) immune levels.

The human MHC contains many other Class I and Class II genes (e.g. HLA-G and HLA-DM, respectively) whose products do not seem important as transplantation antigens (Duquesnoy, N.D.).Today, science has advanced to the point that most transplant operations are considered relatively low risk. The success rate is phenomenal for kidney transplants, liver transplants, cornea transplants, pancreas transplants -- even heart and lung transplants. Clinicians take adequate compatibility tests before the transplantation is done.

Besides post operative monitoring techniques also help the patient in early detection of any signs of rejection and can be treated. Work CitedDepartment of Health and Human Services, Clinical Trials in Organ Transplantation (Ctot) (2003) RFA-AI-04-003, 25 December 2006, Duquesnoy, R.J. Histocompatibility Testing in Organ Transplantation. 25 December 2006, Wikipedia, Organ transplant (2006) Wikimedia Foundation, Inc. 25 December 2006,