MHC class II protein complex binding

Definition

Target type: molecularfunction

Binding to a class II major histocompatibility complex. [GOC:mtg_signal, GOC:vw]

MHC class II protein complexes are integral to the adaptive immune response, specifically in presenting processed antigens to CD4+ T cells. The molecular function of this binding involves a series of intricate steps: 1. **Antigen Processing:** Antigen-presenting cells (APCs) like dendritic cells, macrophages, and B cells internalize exogenous antigens through phagocytosis, endocytosis, or macropinocytosis. These antigens are then processed within endosomes, where they are degraded into peptide fragments by proteases. 2. **Loading of Peptides onto MHC II:** Within endosomes, MHC class II molecules associate with invariant chain (Ii) to prevent premature binding to peptides in the ER. Ii acts as a chaperone, directing MHC II to the endocytic pathway. Upon arrival in the endosome, Ii is progressively degraded, leaving a small fragment called CLIP (class II-associated invariant chain peptide) bound to the MHC II molecule. 3. **Exchange of CLIP for Antigenic Peptides:** The HLA-DM molecule, a chaperone specific to MHC II, facilitates the exchange of CLIP with peptides derived from processed antigens. HLA-DM promotes the dissociation of CLIP and stabilizes the binding of high-affinity antigenic peptides to MHC II. 4. **Surface Expression and Presentation:** Once loaded with antigenic peptides, MHC II molecules are transported to the cell surface. 5. **T Cell Recognition:** CD4+ T cells express TCRs (T cell receptors) that specifically recognize the complex formed between MHC II and the bound antigenic peptide. This recognition activates the T cell, initiating an immune response. In summary, the molecular function of MHC class II protein complex binding involves the processing of exogenous antigens, loading of peptides onto MHC II molecules, and presentation of these peptide-MHC II complexes on the cell surface for recognition by CD4+ T cells, thereby triggering adaptive immune responses.'
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Proteins (7)

Compounds (158)