The different process of class switching and somatic hypermutation and proposed generation of plasma cells in humans.

After B-cell precursors succeed in generating functional antigen receptors in bone marrow, they are released into the B-cell pool as naive B cells. Naive B cells without CD27 undergo oligoclonal expansion, class switching, and somatic hypermutation in GCs, and CD27 is expressed on their surface, which results in their differentiation into memory B cells. Plasma cells generated from memory B cells, which carry a high load of somatic mutation, may produce high-affinity antibodies (IgG, IgM, IgA, IgE). Plasma cells from unmutated B cells outside GCs or through GCs before carrying somatic hypermutation may produce low-affinity antibodies (IgG, IgM, IgE).