T cell receptor on CD4+ T helper cell recognizing CRM197 peptide–MHC II complex (TCR-CRM197-MHCII) (TCR-CRM197-MHCII)

The T cell receptor (TCR) on CD4+ T helper cells that recognizes CRM197 peptide–MHC II complexes is a critical component of the immune response to conjugate vaccines (Bröker et al., 2011). CRM197 is a genetically detoxified version of the diphtheria toxin, containing a G52E mutation, that serves as a highly effective carrier protein for polysaccharide antigens (Pichichero, 2013). When a conjugate vaccine is administered, antigen-presenting cells process the CRM197 protein into peptides and present them via MHC Class II molecules to these specific CD4+ T cells (Avci et al., 2011). The subsequent TCR-mediated activation of these T cells provides essential "help" to B cells, facilitating the production of high-affinity antibodies and the establishment of long-term immunological memory against bacterial pathogens like Streptococcus pneumoniae and Neisseria meningitidis (Stefanetti et al., 2022). This mechanism is fundamental to the efficacy of several widely used pediatric and adult vaccines, transforming T-independent carbohydrate antigens into T-dependent ones (Pollard et al., 2009).

Other names

CRM197-specific T-cell receptorCD4+ T-cell receptor for CRM197TCR recognizing CRM197-MHC II complexCRM197-reactive T-cell receptor

Vaccines containing the CRM197 carrier protein provide peptides that are processed and presented by MHC Class II molecules on antigen-presenting cells. The T cell receptor (TCR) on specific CD4+ T helper cells recognizes these CRM197 peptide-MHC II complexes, leading to T cell activation, proliferation, and the secretion of cytokines (Avci et al., 2011). This activation provides the necessary help to B cells that have recognized the polysaccharide component of the vaccine, enabling them to undergo isotype switching and differentiate into long-lived plasma cells and memory B cells (Pichichero, 2013; Bröker et al., 2011).