B Cell Activation and Differentiation

Naive B cells become sensitized when they encounter their corresponding antigen, which binds to the B cell receptor, or BCR, on the cell surface.

After binding, the B cell engulfs the antigen by receptor-mediated endocytosis, internalizing the antigen-BCR complex.

Inside the B cell, the antigen is processed into smaller peptide fragments and combined with MHC II molecules.

The antigen-MHC II complex is transported for display on the surface of the B cell, completing the sensitization process.

Next, the sensitized B cell binds the TCR on Helper T cells, which release cytokines as a co-stimulatory signal to activate the B cell.

Upon activation, the B cell undergoes clonal expansion, rapidly proliferating to generate identical B cells capable of binding to the same antigen.

Some activated cells differentiate into effector plasma cells, producing antibodies that neutralize the antigen or mark it for destruction.

Simultaneously, other activated B cells differentiate into long-lived memory B cells that provide immunological memory upon future encounters with the same antigen