Multiplicity of potential outcomes following encounter of a B cell with antigen. Antigen, the ligand for the B-cell receptor, varies in properties that influence outcome including avidity, molecular form, concentration, and time of exposure. In the presence of CD40L-expressing Th cells, differentiation and proliferation can occur. In the absence of T-cell help, possible fates of the B cell include activation/maintenance, apoptosis, or anergy with receptor desensitization.