HLA-DRB4

HLA-DRB4 is a human gene that encodes a subunit of the Human Leukocyte Antigen (HLA) – DR isotype, a major histocompatibility complex (MHC) class II cell surface receptor. The HLA-DR molecule is a heterodimer composed of an alpha (DRA) chain and a beta (DRB) chain. HLA-DR is crucial for the adaptive immune system, presenting peptide antigens derived from extracellular proteins to T helper cells.

The DRB4 gene is polymorphic, meaning it exists in multiple allelic variants within the human population. However, unlike other DRB genes such as DRB1, not all individuals possess a functional DRB4 gene. In some individuals, the DRB4 gene is present but not expressed, resulting in no functional DRB4 protein. In others, the DRB4 gene is deleted or pseudogenized.

When expressed, the HLA-DRB4 protein associates with the DRA chain to form the HLA-DR molecule. This molecule then plays a vital role in antigen presentation. The specific peptides that HLA-DRB4 can bind and present are influenced by its allelic variant.

Variations in HLA-DRB4 expression and allelic polymorphisms have been associated with susceptibility or resistance to various diseases, including autoimmune diseases and infectious diseases. For example, certain HLA-DRB4 alleles have been linked to an increased risk of rheumatoid arthritis. The absence of DRB4 expression has also been explored in connection with disease susceptibility. Research continues to investigate the precise role of HLA-DRB4 in immune responses and disease pathogenesis.