Processing of antigen in germinal center B cells

B cells are professional antigen presenting cells in the sense that they process antigens and display the resulting antigen peptides on MHC class II complexes (reviewed in McShane and Malinova 2022, Rastogi et al. 2022). Antigens bound to the B cell receptor (BCR) are internalized, unfolded, and digested by proteases. The resulting peptide fragments are then loaded onto MHC II complexes that are made accessible by the removal of the class II-associated invariant chain peptide (CLIP) from MHC II by HLA-DM. In B cells, trafficking of the BCR:antigen complex is accelerated compared with trafficking of pinocytosed antigens and the antigen processing reactions occur in distinctive multivesicular bodies.

Summary from Reactome (R-HSA-9979719), read 2026-09-23.