B cell subpopulations in the mouse: analysis with monoclonal antibodies NIM-R2 and NIM-R3.

Two rat monoclonal antibodies, NIM-R2 and NIM-R3, have been produced using the rat myeloma line 210RCY3-Ag1.2.3 and spleen cells from Lou rats immunized with mouse spleen cell plasma membrane or cells. The antibodies identify nonoverlapping populations of surface Ig-positive cells in the spleen and a large (95%) proportion of bone marrow cells. Both recognize differentiation antigens in that the surface representation of the markers changes during the development of the cell. The NIM-R3 specificity does not appear until three weeks of age in both the spleen and bone marrow and may be on a more mature set of cells. In contrast, the NIM-R2 antibody, which stains the pre-B cell line 70Z/3 and binds to neonatal cells, may recognize pre-B cells in the bone marrow. There was no clear-cut correlation between the presence or absence of surface IgM, surface IgD or complement receptors on B cells positive or negative for either NIM-R2 or NIM-R3. Most interesting was the finding of identical total surface Ig densities on cells which stained weakly or strongly with NIM-R2, since these two B cell subpopulations are shown to be enriched for memory and virgin B cells, respectively. To bias the production of monoclonal antibodies to distinct populations of cells, the immunogen for the NIM-R3 fusion was depleted of cells strongly reactive with NIM-R2. This method is of general applicability in the production of monoclonal antibodies to complementary populations of cells.