Describe the process of graft rejection in transplantation - Essay Example

Process of Graft Rejection in Transplantation Introduction: Transplantation is a method that can be used to treat any malfunctioning of an organ within the body by transfer of cells, tissues or organs from one place to another (Malhotra, 2011). Graft rejection of transplantation has been obtained as one of the most significant barriers in the process (Graft Rejection, n.d.). The present study focuses on understanding of the process of graft rejection in transplantation. Graft Rejection in Transplantation: Graft rejection in human bodies may be classified as hyperacute rejection, acute rejection or chronic rejection.

Hyperacute rejection that is categorized by thrombotic occlusions and haemorrhage of the graft vasculature occurs as a result of pre-existing host antibodies that remain bonded to antigens found in the graft endothelium. The complement system gets activated through the recognition of the antigens, accompanied by invasion of neutrophils. Coagulation is initiated by the lipid particles that are discarded from the endothelial cells and platelets. The graft gets vascularised through the inflammation that occurs and the graft suffers irreparable damage (Graft Rejection, n.d.).

Acute rejections are common in transplants and usually occur by incompatible HLA antigens found in the cells. T-cells are involved in rejections that result in the production of cytokines by the graft cells that engage other inflammatory cells in the process, and cause necrosis of allograft tissues. In chronic rejections occlusions are visible in graft arteries that are caused by the smooth muscle cells that proliferate and the fibroblasts that produce collagens. This process is known as accelerated or graft arteriosclerosis and that causes fibrosis and can lead to ischemia and cell death (Graft Rejection, n.d.).

Rejection Mechanism:Sensitization and Effector are the two primary stages of the process of the graft rejection process in transplantation. In the sensitization stage, the CD4 and CD8 categories of T-cells use their receptors and identify the alloantigens that are present on the foreign graft cells. The signals required for the process are provided by the interactions between the T-cell receptor and antigen, and co-stimulatory receptor/ligand with T-cell or APC regulator. Peptide-binding grooves are formed by the helices of MHC molecules and these are made in use by the peptides derived from normal cellular proteins.

Direct and indirect pathways of allorecognition cause the production of diverse sets of allospecific clones of T-cell (Malhotra, 2011).The effector mechanisms are supported by the Alloantigen-dependent and independent factors. A nonspecific inflammatory response is created initially that promotes shedding of the MHC molecules leading to indirect pathways and production of antibodies through B-cells. T cell–derived cytokines and macrophages enable the activation of endothelial cells. The MHC molecules that are expressed present antigens that strengthen the process of rejection.

Apoptosis of the target cell is the ultimate step for the cytolytic processes involved in the mechanisms (Malhotra, 2011).Conclusion:The above study reflects on the mechanism or the process of graft rejection that occurs during transplantation. It has been obtained that the process involves the sensitization and effector mechanisms involving the T-cells and antigens and ultimately leads to apoptosis that damages the process and the cells performing in the process causing graft rejection.References1) Graft Rejection (n.d.), biomed, available at: http://biomed.brown.edu/Courses/BI108/BI108_2004_Groups/Group04/Rejection_overview.

htm (accessed on May 4, 2012)2) Malhotra, P. (2011), Immunology of Transplant Rejection- Immunobiology of Rejection, medscape, available at: http://emedicine.medscape.com/article/432209-overview#aw2aab6b5 (accessed on May 7, 2012)3) Malhotra, P. (2011), Immunology of Transplant Rejection- Overview, medscape, available at: http://emedicine.medscape.com/article/432209-overview (accessed on May 4, 2012)