B cells undergo somatic hypermutation and class switching in the germinal center after binding to antigen and activation by helper T cells. Somatic hypermutation introduces random mutations into the B cell receptor which are selected for increased affinity for the antigen. Class switching changes the isotype of antibodies produced, allowing B cells to activate different immune functions. These developmental changes in the germinal center ensure that B cells produce antibodies that are highly specific for and effective at eliminating the invader.