Final answer:
The three pairs of HLA Class II genes are critical for the immune system, enabling it to differentiate between self and non-self entities. They contribute to the diversity of antigen presentation and are crucial for the success of organ transplants.
Step-by-step explanation:
The three pairs of HLA Class II α- and β-chain genes are integral components of the immune system. They play a crucial role in the body’s ability to distinguish between self and non-self.
These genes are highly polymorphic, meaning they have many different alleles within the population, contributing to individual variation in immune responses. In humans, these genes are part of the Major Histocompatibility Complex (MHC) and are known as human leukocyte antigen (HLA) genes.
The importance of matching these genes is especially relevant in organ transplants, where a close match between the HLA genes of the donor and recipient greatly reduces the risk of organ rejection.
The process of forming the T cell receptor (TCR) involves genetic rearrangements bringing together variable (V), diversity (D), and joining (J) gene segments.
The alpha chain of the TCR is made from combinations of different Va and Ja segments, while the beta chain of the TCR is formed from combinations of different Vβ, Dβ, and Jβ segments. This process enables a vast diversity of TCRs, which is essential for the immune system to recognize a wide array of antigens.
Overall, the antigen presentation by MHC molecules is a key part of the immune response, where MHC I molecules present antigens to CD8+ T cells and MHC II molecules present antigens to CD4+ T cells, initiating adaptive immune responses to fight off pathogens.