NIM-R7, a novel marker for resting B1 and marginal-zone B lymphocytes, is also expressed on activated T and B cells

Abstract

In mice, follicular B cells have been studied in detail, while two other B-cell subpopulations - marginal-zone B and B1 cells - are less well understood. In this work we report the expression pattern of p58, a lymphocyte-activation marker, recognized by rat monoclonal antibody, NIM-R7, and present on the latter two cell subpopulations. Staining with NIM-R7 showed that undisturbed marginal-zone B cells, as well as peritoneal cavity and splenic B1a cells, constitutively expressed p58, whereas follicular B cells and resting T lymphocytes did not. Ontogenic analysis of different compartments showed that p58 did not appear at any stage of development, prior to the development of mature T or B2 lymphocytes. Upon polyclonal stimulation, however, p58 appeared on both T and B2 lymphocytes. Finally, ricin A-conjugated NIM-R7 was able to kill the BCL1 lymphoma without effect on mature resting B2 cells. Therefore, p58 may be a potential target for diagnosis or therapy of B1 and marginal-zone B-cell malignancies.

Figure 1

Expression of p58 on splenic B-cell subpopulations. p58 is expressed on marginal-zone (MZ) B cells and on B1a cells, but not on immature B cells (a), while it is expressed on follicular B cells (FO) with activated characteristics (b). A total of 10⁶ B cells, enriched from panning with anti-B220 antibody, were stained with immunoglobulin M antibody (anti-IgM), CD21 antibody (anti-CD21), CD5 antibody (anti-CD5) and NIM-R7 monoclonal antibody (mAb) or an isotype-matched control mAb. The shadow line shows the staining with the isotype-control mAb.

Figure 2

The p58 molecule is expressed on peritoneal cavity B1 cells. p58 is expressed on B cells, but not on T cells from the peritoneal cavity (a). p58 is expressed on B1 cells, defined by immunoglobulin (Ig)M and IgD staining (b), or on B1 cells, as defined by Mac-1 and IgM staining (c). A total of 10⁶ cells were stained with anti-B220 and anti-CD3 (a), anti-IgM and anti-IgD (b), or anti-Mac-1 and IgM (c), and NIM-R7 monoclonal antibody (mAb) or an isotype-matched control mAb. In all panels, a gate in the lymphocyte region (according to size and granularity) is shown. In (b) and (c) the shadow lines show the staining with the isotype control; the thick lines are B2 cells and the thin lines are B1 cells.

Figure 3

The p58 molecule is expressed upon lymphocyte activation. p58 is expressed on anti-CD40 activated (a), lipopolysaccharide (LPS)-activated (b), or concanavalin A (Con A)-activated (c) B cells, and on Con A-activated T cells (d). A total of 10⁶ cells were activated for 0, 24, 48, 72 or 96 hr, and then stained with anti-B220 or anti-CD3 and NIM-R7 monoclonal antibody (mAb) or an isotype-matched control mAb. The analysis was performed on activated cells (according to size and granularity). Shadow histograms show the staining with the isotype control.