Dissociation of murine B-cell proliferation and differentiation by monoclonal antibody, NIM R2

The rat monoclonal antibody NIM-R2 has been shown to be directed towards a cell surface differentiation antigen of murine B lymphocytes which is expressed to a greater or lesser extent at different phases of B-cell activation. In this report, NIM-R2 is shown to be capable of modulating the functional capacity of B cells. In the presence of the monoclonal antibody, the ability of fully mature antibody-forming cells to secrete their product is inhibited. This effect is, however, short-lived, with the cells quickly recovering secretory capacity, even in the continued presence of the monoclonal antibody. NIM-R2 also inhibits the generation of antibody-forming cells in culture, the addition of antibody as late as the third day of a 4-day culture period being effective in this respect. The evidence presented here suggests that these inhibitory effects of NIM-R2 are mediated through interference with separate mechanisms. Our data also indicate that, although NIM-R2 inhibits the generation of antibody-forming cells from their B-cell precursors, it does not affect the B-cell proliferative response. The findings are discussed in terms of their relevance to current models of B-cell activation and differentiation.