Abstract

The Major Histocompatibility Complex (MHC) plays a central role in the regulation of immune responses by mediating the presentation of antigenic peptides to T lymphocytes. Divided into MHC Class I and Class II molecules, this complex ensures the distinction between self and non-self, enabling the immune system to mount precise and effective responses against pathogens. MHC Class I molecules present endogenous antigens to CD8+ cytotoxic T cells, while MHC Class II molecules present exogenous antigens to CD4+ helper T cells, initiating distinct yet coordinated immune pathways. The polymorphic nature of MHC genes contributes to immune diversity but also underlies challenges in organ transplantation and susceptibility to autoimmune diseases. This review explores the molecular mechanisms of MHC-mediated antigen presentatio