Nonresponsiveness of immature B lymphocytes to anti-immunoglobulin is reversed by pronase.

Splenic B cells are induced to proliferate upon culture with antibody having specificity for surface membrane immunoglobulins. Cells treated with pronase, washed and then cultured with antibody, exhibited a greater than 5-fold enhancement of DNA synthesis whereas pronase treatment, per se, was not mitogenic. The pronase effect exhibited specificity in that the induction of proliferation with either lipopolysaccharide or dextran sulfate was not enhanced by prior enzyme treatment. Cells from mice at two weeks of age which essentially do not show a proliferative response to antibody become responsive subsequent to pronase treatment. These results are interpreted to suggest a possible growth regulatory role for the pronase sensitive surface membrane component.