Cross-reactive material 197 peptide-MHC class II complex (CRM197-MHC II)

Cross-reactive material 197 (CRM197) is a genetically detoxified mutant of the diphtheria toxin (DT) that serves as a primary carrier protein in numerous conjugate vaccines [1]. When these vaccines are administered, antigen-presenting cells (APCs) such as dendritic cells and B cells internalize the conjugate via endocytosis and process the CRM197 protein into peptide fragments through proteolytic degradation [2]. These CRM197-derived peptides are subsequently loaded onto Major Histocompatibility Complex (MHC) class II molecules within the endolysosomal compartment and transported to the cell surface [3]. The resulting CRM197 peptide-MHC II complex acts as a specific ligand for the T-cell receptors (TCRs) of CD4+ T-helper cells [1]. This recognition event is crucial for providing the necessary co-stimulatory signals and cytokines required for B-cell activation, class switching, and the generation of high-affinity memory B cells against the conjugated polysaccharide antigen [3]. Consequently, this complex is the functional unit that converts T-cell independent antigens into T-cell dependent ones, ensuring long-term protective immunity against bacterial infections [2]. The interaction between the TCR and the CRM197-MHC II complex is a fundamental mechanism in the efficacy of vaccines like Prevnar and Menveo [1]. [1] Bröker M, et al. (2011). Biologicals. [2] Shinefield HR. (2010). Vaccine. [3] Avci FY, et al. (2011). Nature Medicine.

Other names

CRM197-MHC II complexCRM197-peptide-MHC-IIDiphtheria toxin CRM197-MHC II complexCRM197-derived peptides presented by MHC II

The complex acts as a ligand for T-cell receptors (TCR) on CD4+ T-helper cells, triggering T-cell activation and subsequent cytokine release to support B-cell antibody production.