Major histocompatibility complex class I and class II antigen presentation (MHC class I / MHC class II)

Major histocompatibility complex class I and class II proteins are transmembrane glycoproteins responsible for presenting antigenic peptides to T cells, constituting a pivotal aspect of adaptive immunity. MHC class I molecules are expressed on all nucleated cells and present endogenously derived antigens to CD8+ cytotoxic T cells, allowing recognition and elimination of infected or transformed cells[2][1][5]. MHC class II molecules are expressed mainly on professional antigen-presenting cells (dendritic cells, macrophages, B cells) and present exogenously derived peptides to CD4+ helper T cells, orchestrating the activation and regulation of immune responses[1][3][6][7]. Their extreme polymorphism underlies individual differences in immunity, susceptibility to autoimmune disease, and transplant compatibility[3][6]. Dysregulation of these pathways contributes to cancer immune escape, autoimmunity, and immunodeficiency. No drugs directly target these proteins, but many immunotherapies rely on their intact function[5][3].

Other names

MHC class I proteinMHC class II proteinHLA class IHLA class IIMajor histocompatibility complex proteinsAntigen-presenting moleculesHistocompatibility antigens

Enhancement of antigen presentation (by increasing MHC expression, e.g. interferon gamma) Blocking immune checkpoints (restores T cell ability to recognize MHC-presented antigens) Restoration of antigen presentation machinery (experimental cancer therapy approaches)