MARGINAL ZONE B-CELLS EXHIBIT UNIQUE ACTIVATION, PROLIFERATIVE AND IMMUNOGLOBULIN SECRETORY RESPONSES

Mouse splenic B cells can be separated based on their distinctive expr ession of cell surface antigens, Marginal zone (MZ) B cells are CD38(h igh) CD21(high) CD23(low/-), while follicular (FO) B cells are CD21(in t) CD23(int) and newly formed (NF) B cells are CD21(dun/-) CD23(-). Ex ploiting these phenotypic distinctions, we isolated the three B cell s ubsets and assessed their Other phenotypic differences and functional capabilities in vitro. FO B cells proliferate more than the other B ce ll subsets in response to either IgM or CD38 cross-linking, MZ B cells proliferate better than FO B cells when stimulated with lipopolysacch aride (LPS), sub-optimal levels of LPS and CD38 cross-linking or CD40 ligation. When NE FO and MZ B cells were stimulated with either LPS or LPS and interleukin-4, MZ B cells secreted more IgM and IgG3 than the other two subsets, Similarly, calcium fluxes measured within MZ B cel ls are larger in amplitude and more sustained after B cell receptor cr oss-linking than those found in the other two subsets. Collectively, t hese results indicate that CB38(high) CD21(high) CD23(low/-) MZ B cell s are specially suited to play a unique role in response to antigens d elivered to the MZ area.