HLA (Human Leukocyte Antigen) class II LB antigens are a subset of HLA class II proteins, which are essential for the immune system's recognition and elimination of pathogens. They are found on the surface of antigen-presenting cells, such as B cells, macrophages, and dendritic cells. HLA class II molecules are encoded by genes within the major histocompatibility complex (MHC) region on chromosome 6 in humans.
The LB antigens are polymorphic, meaning they exist in different variants or alleles in the population, contributing to individual variability in immune responses. They consist of two chains, an alpha chain (encoded by HLA-DMA, HLA-DMB genes) and a beta chain (HLA-DLA, HLA-DLB genes). These two chains combine to form a heterodimeric protein complex.
HLA LB antigens play a crucial role in the immune response by presenting processed antigens to CD4+ T cells. They bind and present peptide antigens derived from pathogens, such as bacteria or viruses, to T cell receptors, thereby triggering an immune response. This interaction serves to activate T helper cells, leading to the production of cytokines that further stimulate immune responses, including the activation of other immune cells.
Due to their genetic polymorphism, HLA LB antigens are significant in tissue and organ transplantation, as they are used to match donors and recipients to minimize the risk of graft rejection. HLA typing, based on the identification of specific HLA alleles, is critical for selecting suitable donors and optimizing transplantation outcomes.
