Mitogenic response of neoplastic B cells: comparison of reactivity to Staphylococcus aureus Cowan I and anti-immunoglobulin antibodies.

Neoplastic B cells from two patients with hyperleucocytic hairy cell leukaemia (HCL) and 19 patients with chronic lymphocytic leukaemia of B cell Type (B-CLL) were investigated to examine the mitogenic responses to the F(ab')2 fraction of anti-human immunoglobulins (anti-Igs) and Staphylococcus aureus Cowan I (STA). Neoplastic cells from both HCL patients lacked surface Tac antigen. Mononuclear cells from the two HCL patients strongly responded to both anti-Igs and STA as measured by 3H-thymidine incorporation in vitro. Although the mononuclear cells from two patients with B-CLL showed high response to STA, cells from none of the patients with B-CLL responded to anti-Igs. Mononuclear cells as well as T-cell-depleted fractions from the two HCL patients showed a strong proliferative response by anti-gamma chain antibody (anti-gamma) and the mononuclear cells from one of the patients were also induced to proliferate by anti-delta, whereas those from normal subjects responded only to a high concentration of anti-mu. Based on the difference in reactivity to anti-Ig, it is suggested that the HCL cells in this study originate from a subset equivalent to 'memory' B cells, whereas the B-CLL cells originate from a subset equivalent to 'virgin' B cells.