Figure 1.

Mechanism of action for initiation of humoral immune responses to a target antigen aided by a secondary helper antigen when they are conjugated together (a) and spatially segregated by use of a liposome (b). (1) B cell with specific B cell receptor (BCR) for target/helper antigen binds to vaccine particle; (2) B cells engulf and digest vaccine particles; (3) vaccine particle antigens are presented on B cells class II major histocompatibility complexes (MHC II) for helper T cell recognition with specific T cell receptor (TCR) for presented antigen; (4) upon TCR binding, T cells produce ‘help’ signals to stimulate B cell differentiation; (5) B cells differentiate into plasma cells that secrete antibodies exclusively targeting antigen recognized by BCR in step 1.