Marginal zone B cells exhibit unique activation, proliferative and immunoglobulin secretory responses

Mouse splenic B cells can be separated based on their distinctive expression of cell surface antigens. Marginal zone (MZ) B cells are CD38high CD21high CD23low/−, while follicular (FO) B cells are CD21int CD23int and newly formed (NF) B cells are CD21dim/− CD23−. Exploiting these phenotypic distinctions, we isolated the three B cell subsets and assessed their other phenotypic differences and functional capabilities in vitro. FO B cells proliferate more than the other B cell subsets in response to either IgM or CD38 cross‐linking. MZ B cells proliferate better than FO B cells when stimulated with lipopolysaccharide (LPS), sub‐optimal levels of LPS and CD38 cross‐linking or CD40 ligation. When NF, 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 cells are larger in amplitude and more sustained after B cell receptor cross‐linking than those found in the other two subsets. Collectively, these results indicate that CD38high CD21high CD23low/− MZ B cells are specially suited to play a unique role in response to antigens delivered to the MZ area.