B-lymphocyte differentiation, using pokeweed mitogen stimulation: in vitro studies in leukemic and normal cattle.

B-lymphocytes from 7 normal cattle and from 3 persistent lymphocytotic, 6 lymphosarcomatosus, and 3 bovine leukemia virus-infected animals with diverse defects in humoral immunity were examined for their capacity to undergo terminal differentiation in vitro. Pokeweek mitogen-stimulated cells from normal and leukemic cattle were stimulated to synthesize and secrete immunoglobulins, and these were detected by radial immunodiffusion. Lymphocytes from normal cattle synthesized more IgM than those from persistent lymphocytotic-, lymphosarcomatous-, and bovine leukemia virus-infected cattle. Leukemic cattle have a higher percentage of cells containing intracytoplasmic immunoglobulins; most cells are believed to contain IgG. The serum IgM in normal cattle is significantly (P less than 0.05) higher than that in leukemic cattle. The results indicate that there is an abnormality either in synthesis or secretion of IgM or in abnormal catabolism of Ig from leukemic B-lymphocytes.