Topic: Humoral and cell mediated immunity.
Question: Provide the significance of MHC in transplantation.
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MHC stands for Major Histocompatibility Complex. It refers to a group of genes that encode MHC proteins found on the surface of cells in vertebrate species including humans.
– MHC proteins help the immune system recognize cells as either self or foreign/non-self.
– There are two main classes of MHC proteins – MHC class I and MHC class II.
– MHC class I proteins are found on all nucleated cells. They present intracellular peptides to cytotoxic T cells.
– MHC class II proteins are mainly present on immune cells like macrophages, dendritic cells and B cells. They present extracellular peptides to helper T cells.
– The specific MHC makeup of an individual is known as MHC haplotype. This is genetically determined.
– MHC genes are highly polymorphic, meaning there are many alleles and variations within a population.
– Each person inherits a set of MHC genes from each parent, contributing to one’s unique MHC haplotype.
– MHC compatibility is matched prior to organ transplants to lower risk of rejection. MHC matching is done through genetic testing.
– Different ethnic groups have certain MHC alleles more commonly than others.
MHC (major histocompatibility complex) proteins play a critical role in transplantation and graft rejection.
– MHC proteins help immune system recognize “self” vs “foreign” cells.
– MHC mismatch between donor and recipient cells is a major trigger for graft rejection.
– Greater the MHC mismatch, more aggressive the immune response and faster the graft rejection.
– MHC matching between donor and recipient is done to reduce risk of rejection. Better MHC matching improves graft survival.
– However, even with MHC matching, immunosuppression is required to prevent graft rejection.
– MHC antigens provoke both cell-mediated immune response via T-cells as well as antibody mediated response (B cells).
– Newer immunosuppressive drugs target the T-cell activation pathway triggered by MHC mismatch.
