Hybridoma 2.4G2: dissociation of the B-lymphocyte-triggering activity from the monoclonal anti-Fc IgG receptor antibody.

Previously, we have reported that monoclonal antibody specific for mouse Fc IgG receptors (Fc gamma R) [purified by affinity chromatography using goat F(ab')2 anti-rat Ig linked to Sepharose from supernatants of hybridoma 2.4G2] can induce both proliferation and antibody secretion of normal B-lymphocytes in the absence of T-lymphocytes. The current studies have shown that the B-cell-triggering activity is associated with a substance produced by 2.4G2 which can be distinguished from the 2.4G2 antibody by several criteria: (1) different preparations of 2.4G2 antibody with identical binding capacity for Fc gamma R differ markedly in their ability to trigger B-lymphocytes; (2) the B-lymphocyte-triggering substance and the anti-Fc gamma R antibody can be separated using insolubilized monoclonal mouse anti-rat kappa-antibody columns; and (3) the B-lymphocyte-triggering substance has a mol. wt of less than 50,000, while the 2.4G2 antibody has a mol. wt of 160,000. The B-lymphocyte-triggering moiety produced by the 2.4G2 hybridoma may be a previously undescribed lymphokine.