In vitro proliferative response of chronic lymphocytic leukemia.

The peripheral blood lymphocytes of 13 previously untreated chronic lymphocytic leukemia (CLL) patients showed a decreased and delayed response in vitro to plant mitogens (PHA and PWM) and specific antigens (PPD and MLC). In addition, the serum of these patients inhibited the mitotic reactivity of both autologous and homologous normal lymphocytes. Since incubation with CLL serum did not affect the SRBC-rosetting capacity of normal lymphocytes, we believe that CLL serum interferes with some metabolic stage in blastogenesis rather than at the level of mitogen membrane interaction. The in vitro transformation of lymph node, bone marrow and peripheral blood lymphocytes in some of these patients was also investigated. Stimulation of peripheral blood cells with plant mitogens resulted in a more serious impairment of the response than that found with bone marrow and lymph node cells. This could be explained by the fact that, although CLL is a widespread lymphoproliferative disorder, some preferential homing of normally reactive cells in the bone marrow and lymph nodes cannot be excluded. Finally, since no stimulation was observed in mixed leukocyte cultures (MLC), our experiments provide evidence that no antigenic differences are detectable in CLL lymphoid populations.