CRM197-derived peptides-MHC class II complex (CRM197-MHCII)

CRM197-derived peptides bound to MHC class II on antigen-presenting cells (APCs) represent the functional immunological unit responsible for the efficacy of many conjugate vaccines (Source: PubMed, PMID: 21763474). CRM197 is a non-toxic mutant of the diphtheria toxin, containing a single amino acid substitution (Gly52Glu) that eliminates its ADP-ribosyltransferase activity while preserving its potent immunogenicity (Source: UniProt, P00588; PubChem, CID 131751341). When used as a carrier protein, CRM197 is internalized by APCs such as dendritic cells and B cells, where it undergoes endosomal processing into various peptide fragments. These peptides are then loaded onto MHC class II molecules and displayed on the cell surface to be recognized by specific CD4+ T helper cells (Source: PubMed, PMID: 20620244). This recognition is crucial for providing 'T-cell help,' which facilitates B-cell differentiation into plasma cells and the generation of high-affinity, long-term memory antibodies against the attached vaccine antigens, such as bacterial polysaccharides (Source: PubMed, PMID: 21111630). This mechanism is fundamental to the prevention of diseases like pneumonia and meningitis in pediatric and adult populations.

Other names

Cross-reacting material 197 peptidesCRM197-MHC II complexDiphtheria toxin CRM197 fragments on MHC IICRM197-derived T-cell epitopesCRM197-MHC class II complex

The complex acts as a ligand for T-cell receptors (TCRs) on CD4+ T helper cells, triggering signal transduction that leads to cytokine release and B-cell maturation for antibody production against conjugated antigens (Source: PubMed, PMID: 21111630).