Major Histocompatibility Complex (MHC) class I and II pathways (MHC-I and MHC-II pathways)

The Major Histocompatibility Complex (MHC) class I and II pathways are fundamental biological processes responsible for the processing and presentation of peptide antigens to the adaptive immune system [1.1.1, 1.3.1]. MHC class I molecules are expressed on nearly all nucleated cells and present endogenous peptides to CD8+ cytotoxic T cells, facilitating the detection of intracellular pathogens and malignant transformations [1.3.4, 1.3.5]. MHC class II molecules are primarily found on professional antigen-presenting cells, such as dendritic cells and macrophages, and present exogenous peptides to CD4+ helper T cells to orchestrate complex immune responses [1.1.1, 1.2.1]. These pathways are critical for maintaining self-tolerance and initiating defense against infections and tumors [1.3.3, 1.3.4]. Dysregulation of MHC pathways, such as the downregulation of MHC class I or the loss of Beta-2 microglobulin, is a common mechanism of immune evasion in cancer and viral infections [1.1.3, 1.2.2]. Therapeutic strategies targeting these pathways include vaccines to enhance antigen presentation, interferons to upregulate MHC expression, and immunosuppressants to prevent the rejection of transplanted tissues or to treat autoimmune disorders [1.2.1, 1.2.3, 1.3.1].

Other names

HLA class I and II pathwaysAntigen presentation pathwaysMHC-I and MHC-II antigen processing and presentationHuman Leukocyte Antigen pathways

Modulation of antigen presentation through induction of MHC expression, inhibition of T cell activation, or bypassing MHC-restricted recognition [1.2.1, 1.3.2].