Activation and proliferation signals in mouse B cells I. A comparison of the capacity of anti‐Ig antibodies or phorbol myristic acetate to activate B cells from CBA/N or normal mice into G1

Abstract

B lymphocytes from the CBA/N mouse do not synthesize DNA when cultured with anti‐Ig antibodies. However, these cells like normal B cells, do manifest increased Ia antigen expression and RNA synthesis (i.e. enter G₁) when stimulated by anti‐Ig, even at doses which are nonmitogenic for normal B cells. Pretreatment of both normal and CBA/N B cells with anti‐Ig also primes them to give an enhanced proliferative reponse to lipopolysaccharide (LPS). The tumor promoter phorbol myristic acetate (PMA) also enhances RNA synthesis and Ia antigen expression in B cells from both normal and CBA/N mice. However, PMA only primes CBA/N B cells to respond to LPS: pretreatment of normal B cells with PMA causes a modest suppression of LPS‐induced, and a marked suppression of anti‐Ig induced, DNA synthesis. These results therefore confirm and extend earlier data showing that there are distinct activating (G₀ to G₁) vs. proliferative (G₁ to S) signals discernible in B cells. They also suggest that the activation mechanism of CBA/N B cells is subtly different from that of any known subpopulation of normal B cells.