Major Histocompatibility Complex Class I and Class II molecules (MHC I and MHC II)

Major Histocompatibility Complex (MHC) Class I and Class II molecules are cell surface glycoproteins essential for the adaptive immune system's ability to recognize foreign antigens (Pixorize, 1.1.1). MHC Class I molecules are expressed on nearly all nucleated cells and present endogenous peptides, such as those from viruses or mutated cancer proteins, to CD8+ cytotoxic T cells (Osmosis, 1.1.2). In contrast, MHC Class II molecules are primarily restricted to professional antigen-presenting cells, including dendritic cells and macrophages, where they present exogenous antigens to CD4+ helper T cells (Microbe Notes, 1.1.3). These molecules are critical for immune surveillance, ensuring that the immune system can identify and eliminate infected or malignant cells while maintaining tolerance to self-tissues (Wikipedia, 1.1.4). Dysregulation of MHC expression or function is linked to various pathologies, including autoimmune diseases, where self-antigens are inappropriately presented, and cancer, where tumors downregulate MHC to evade immune detection (News-Medical, 1.2.4). Therapeutic interventions include vaccines that leverage MHC presentation to elicit immunity, immunosuppressants that modulate downstream T-cell activation, and drugs like glatiramer acetate that competitively bind to MHC molecules to treat autoimmunity (Ovid, 1.3.1; Rapid Novor, 1.3.2).

Other names

Human Leukocyte AntigenHLAAntigen-presenting moleculesMHC moleculesHLA-AHLA-BHLA-CHLA-DPHLA-DQHLA-DR

Antigen presentation to T cells, competitive binding to the peptide-binding groove, and modulation of T-cell receptor signaling (NIH, 1.2.1; Ovid, 1.3.1).