Effects of staphylococcal protein A-treated human leukemic serum on autologous leukemic blast growth and mitogenesis of lymphocytes.

Sera and leukemic blasts of 14 patients with acute myelogenous leukemia were stored at -70 degrees C. In eight patients in whom a remission was achieved, peripheral blood lymphocytes were cultured together with irradiated autologous leukemic cells in treated serum (serum adsorbed with protein A Sepharose) or control serum (Sepharose-treated). Lymphocyte activation was determined after 7 days in culture by [3H]thymidine incorporation. In the absence of stored leukemic blasts, significantly more [3H]thymidine incorporation occurred in six of the eight patients' lymphocytes cultured in treated serum compared to control. Enhanced activity was observed in all eight patients when irradiated leukemic blasts were cocultured with autologous lymphocytes in treated serum. In five patients, the addition of 10% or more of control serum to treated serum inhibited lymphocyte mitogenesis. Protein A immunoadsorption may allow increased stimulation of acute myelogenous leukemia remission peripheral blood lymphocytes, which is further enhanced in some patients by the presence of autologous leukemic cells. This change in lymphocyte activation may contribute to the antitumor effects of treating serum with protein A.