Compose a 1750 words assignment on current development and the importance of the major histocompatibility complex in transplantation. Needs to be plagiarism free! Two classes of the MHC are recognized, Class I and Class II MHC molecules, which belong to the Immunoglobulin Supergene Family. T-cell receptors, immunoglobulins, CD4, CD8, and others also belong to this family.
Class I and class II molecules show specificity in their binding. MHC class I molecules specifically bind CD8 molecules, which are expressed on cytotoxic TC lymphocytes, while MHC class II molecules specifically bind CD4 molecules, which are expressed on helper TH lymphocytes (Sears DW, Christensen SR, 1997.)
Genes, which are located on human chromosome 6 encodes for the MHC. The BCA region encodes for Class I molecules, while the D region encodes for class II molecules. The region present in between BCA and D region on chromosome 6 encodes class III molecules, including some complement components (Major Histocompatibility, n.d.)
Extensive research has clarified the understanding of the cis-elements and transcription factors that regulate the expression of Class II MHC genes. The discovery of CIITA, a known- DNA binding activator of transcription that is a master control gene for class II gene expression is a crucial discovery. (Radosevich M, Ono SJ, 2003)
Both B cells and T cells have the ability to recognize and respond to antigens with the help of special receptor molecules, which are present on their surface.
In the B cell, this receptor is an antibody-like receptor, which allows the B cell to interact with an antigen in the blood or other body fluids. In contrast, the T cell receptor is more complex (Immune System Series, n.d.)
T-Cell Receptor (TCR) Molecules
TCR is composed of two, disulfide-linked polypeptide chains, alpha, and beta, each having separate, constant and variable domains. The variable domain is made of three hypervariable regions, which are responsible for antigen recognition.
Although the TCR allows T-cells to recognize their particular antigenic moiety, the T-cells need help to recognize the antigen. After the antigenic determinant is presented by an MHC molecule, the signal is passed to the CD3 molecule and then to the T-cell, which causes T-cell activation and lymphokine release. Therefore, antigen recognition by T cells is said to be “MHC-restricted”, since the TCR requires interactions with MHC.