Antigen Activation of Effector phase recognition B lymphocytes Effector cells antibody secreting Helper T cells cells other stimuli Antibody Clonal secretion Naive IgM+ IgD+ expansion o IgG IgG B cell →-的 celle Class switching Activated B cell Microbe →◎x Affinity maturation High-affinit Ig-expressing B cell High Affinity IgG Memory B cell (ElsevierAbbas&LichtmanBasicImmunologyupDated2e-www.studentconsult.com Phases of humoral immune responsesPhases of humoral immune responses Effector phase