Memory B cells and CD27

Following antigen activation in germinal centers, B cells develop into memo ry B cells or plasma cells. Triggering via B-cell immunoglobulin receptors by antigens, cytokines and direct cell-to-cell contact by B and T cells pla ys an important role in the B cell differentiation into memory or plasma ce lls. Adult human peripheral blood B cells are separated into three subtypes by the expression of IgD and CD27, which belong to the tumor necrosis fact or receptor (TNFR) family: IgD+ CD27-naive B cells, IgD+ CD27+ and IgD- CD2 7+ B cells. CD27+ B cells are larger cells with abundant cytoplasm carrying somatic hypermutation, and have an ability to produce immunoglobulin, indi cating that CD27 is a memory marker of B cells. The ligation of CD27 yields crucial signals that positively control the entry of B cells into the path way to plasma cells. We review observations on subpopulations and different iation of mature B-cells by T/B cell interaction via CD27/CD70 as compared with CD40/CD154 interaction, and discuss about memory B cells.