MHC I: Presenting Intracellular Antigens
MHC I molecules are expressed on nearly all nucleated cells and consist of an alpha chain paired with β2-microglobulin (B2M). The alpha chain includes three domains (α1, α2, α3), with α1 and α2 forming a peptide-binding groove that holds peptides (8–10 amino acids) from intracellular sources, such as viral proteins or tumor antigens. These MHC I-peptide complexes are recognized by the T-cell receptor (TCR) on CD8+ cytotoxic T cells, triggering targeted cell destruction. The TCR’s affinity for monomeric MHC I-peptide complexes is low but is significantly enhanced with MHC I tetramers, improving immune detection.
MHC I is essential for antiviral immunity, tumor surveillance, and transplant compatibility. Dysregulation of MHC I presentation can lead to immune evasion in cancers or contribute to autoimmune diseases.
MHC II: Orchestrating Adaptive Immunity
MHC II molecules are primarily found on antigen-presenting cells (APCs) like dendritic cells, macrophages, and B cells. Composed of α and β chains, the α1 and β1 domains form the peptide-binding groove, which binds extracellular antigens (13–25 amino acids), such as bacterial peptides. MHC II presents these antigens to CD4+ T helper cells, which coordinate immune responses by activating B cells for antibody production and macrophages for pathogen clearance.
MHC II is crucial for immunity against extracellular pathogens and is often implicated in autoimmune diseases like rheumatoid arthritis due to genetic polymorphisms.
MHC III: Supporting Immune Regulation
MHC III genes encode proteins that support immune regulation rather than antigen presentation. These include complement components (C2, C4, factor B), cytokines (e.g., TNF-α), and heat shock proteins. Positioned between MHC I and MHC II regions, MHC III proteins enhance innate immunity, inflammation, and immune signaling, complementing the adaptive roles of MHC I and MHC II.
Variations in MHC III genes are linked to inflammatory disorders, making them a key focus for immune modulation research.
Custom MHC I Complex Services at InnoTrace
InnoTrace offers custom MHC I complex services to support advanced immunological research. Leveraging our eukaryotic expression platform (HEK293), we ensure natural conformations for MHC I complexes, avoiding issues like incorrect folding associated with prokaryotic systems. Our process includes:
