Immunology Case Study

Immunology Case Study
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Immunology Case Study
Introduction
Transplantation refers to the act and process of transferring allografts (in the form of organs, tissue and cells) from one site of the body to another site of a different body of the same species but different genotype. Typically, allografts are used to correct body malfunctions whereby a nonperforming pancreas, lung, heart, liver or kidney is replaced by a healthy organ from another body (Kumar, 2015). Despite transplant intentions to correct body malfunctions, it is common for the immune system to act as a barrier that characterizes rejection of transplants through an effective and elaborate mechanism that combats foreign factors (Coico & Sunshine, 2009). Therefore, the body makes use of the immune system to reject transplant results since they are recognized as foreign agents despite being use to address body malfunctions.
Explanation
Understanding the mechanism of allograft rejection is important to biological and medical sciences since it facilitates the use of transplant as an appropriate treatment. In addition, knowledge of this mechanism is crucial in developing suitable stratagems for lessening rejection and in developing new therapies that blunt immune response to allograft transplants, in so doing ensure their longer viability and survival (Kirk et al., 2014; Kumar, 2015). This is based on the awareness that an allograft is a tissue or organ from a donor who is not an identical twin but has healthy cells that would guarantee normal functioning of the body.

This follows the understanding that the human body is resilient and capable of repairing malfunctions, but there are occasions when the malfunctions go beyond its capacity to mount a repair. In such cases, an allograft is necessary to repair the damage that the body has undergone by surgically transplanting tissues and cells from healthy individuals to unhealthy persons by targeting the diseased parts of the body (Veroux, M. & Veroux, P., 2012).
Discussion
Allografts rejection is the result of an immune response to transplanted organs that are seen as foreign agents. The immune response comprises of antibody-mediated (humoral) and lymphocyte-mediated (cellular) approaches. In addition to the two approaches, T cells are also involved in the immune response to reject allografts. The identified approaches produce histocompatibility antigens, products of histocompatibility genes that are encoded on more than 40 loci with most of them located in the major histocompatibility complex (MHC). Within human subjects, the MHC is situated on the short arm of chromosome six, is responsible for causing the strongest reaction and is called the human leukocyte antigen (Morris & Knechtle, 2014). Other antigens have been reported to cause weaker immune reactions, although they cause stronger rejection reactions when used in combination of more than one antigen. It is important to note that the genes that code for MHC are co-dominantly expressed, to imply that the two alleles for each gene are equally expressed on the cell surface. Besides that, these genes are somatically inherited from each parent as haplotypes (Wilkes & Burlingham, 2012).
Human leukocyte antigens are presented in two groups of molecules. The first group is expressed on nucleated cells while the second group in expressed on antigen presenting cells (APCs) to include B cells, activated macrophages, and dendritic cells. The molecules have the unique psychological function of presenting antigenic peptides to T lymphocytes since these cells only recognize antigens when they are presented as complexes combined with MHC molecules. The first group of molecules presents the antigenic peptides from within the cells (such as antigens from self-antigens, tumor antigens, and intracellular viruses) to CD8 T lymphocytes. The second group of molecules presents the antigenic peptides from outside the cells to CD4 T lymphocytes (McKay & Steinberg, 2010; Wilkes & Burlingham, 2012).
It is important to note that allografts transplant rejection cannot be wholly eliminated although there is always the possibility of partial tolerance. The tolerance includes down-regulating immune response, developing suppressor lymphocytes, and anergy as well as a clonal deletion in donor specific lymphocytes. Other than the describes approaches, other tolerance approaches have been postulated to include continued presentation of donor-derived dendritic cells within the allograft recipient to stimulate immunological mediated chimeric states between the transplanted organ and recipient (Wilkes & Burlingham, 2012).
Allograft rejections are typically minimized through two principal approaches (cross-matching and tissue typing) that are conducted prior to the transplantation. These approaches evaluate the compatibility of the recipients and donors, checking the blood groups and human leukocyte antigens compatibility. There are four compatibility evaluation tests that can be carried out. The first test is the mixed lymphocyte reaction that evaluates MHC compatibility, although it is rarely used as a standard test owing to its slowness. The second test is the panel reactive antibody that tests the serum for lymphocytic antibodies against a random cell panel with those who have reported pregnancies, transplants and transfusions having a greater degree of sensitization to reduce the possibility of rejection (Morris & Knechtle, 2014). The third test is the lymphocytotoxicity assay where the donor’s lymphocytes are tested for reactivity against the recipient’s sera with a negative cross good indications of the transplant being accepted. The final test is the blood group compatibility test (Bowden, Liungman & Snydman, 2012).
Other than the four tests, the possibility of rejection can be reduced through the administration of immunosuppressive medication that is presented in two phases. The first phase is known as the initial induction phase where very high doses of the medication are administered. The second phase involves the administration of lower doses of the drug to maintain their presence in the body. Some of the immunosuppressive drugs used in allograft surgeries include corticosteroids, antibodies, antiproliferative agents, mammalian target of rapamycin (mTOR) inhibitors, and immunophilin-binding agents (Kirk et al.,m 2014).
Conclusion
One must accept that allograft transplantation is an important medical process since it enables the body to continue functioning normally by replacing diseased body organs to facilitate normal functioning. In addition, one must acknowledge that transplant also present the possibility of rejections by making use of the body’s defense mechanism to mount a resistance against the graft that is viewed as a harmful foreign body. The rejection makes use of MHC. By understanding the mechanism of allograft rejection, it is possible to develop strategies for addressing it, focusing on cross-matching and tissue typing after tests have been conducted to ascertain the likelihood of rejection. In addition, immunosuppressive medication can be used to minimize rejection. Therefore, an immune system that is functioning at the optimum level reduces the likelihood of allograft rejection by recognizing it as a foreign body and mounting an immune response.

References
Bowden R., Ljungman, P. & Snydman, D. (2012). Transplant Infections. Philadelphia, PA: Lippincott Williams & Wilkins.
Coico, R. & Sunshine, G. (2009). Immunology: A short course (6th ed.). Hoboken, NJ: John Wiley & Sons.
Kirk, A., Knechtle, S., Larsen, C., Madsen, J., Pearson, T. & Webber, S. (2014). Textbook of Organ Transplantation. Hoboken, NJ: Wiley Blackwell.
Kumar, S. (2015). Essentials of Microbiology. New Delhi: The Health Sciences Publishers.
McKay, D. & Steinberg, S. (2010). Kidney Transplantation: A Guide to the Care of Kidney Transplant Recipients. New York, NY: Springer.
Morris, P. & Knechtle, S. (2014). Kidney Transplantation – Principles and practice (7th ed.). Edinburg: Elsevier Saunders.
Veroux, M. & Veroux, P. (2012). Kidney Transplantation: Challenging the future. Sharjah, UAE: Bentham Science Publishers.
Wilkes, D. & Burlingham, W. (2012). Immunobiology of Organ Transplantation. New York, NY: Kluwer Academic/Plenum Publishers.