Phytohaemagglutinin stimulation of peripheral lymphocytes in children with acute lymphoblastic leukaemia during remission.

PHA response in vitro of peripheral blood lymphocytes from patients with ALL was determined during remission by 3H-thymidine uptake. Short courses of intensive treatment with rubidomycin, vincristine, and prednisone significantly diminished both the PHA response and the number of circulating lymphocytes. PHA stimulation restored itself rather quickly after the cytostatic treatment. Maintenance therapy with 6-mercaptopurine, methotrexate, or cyclophosphamide did not cause a significant change in PHA response. The results are discussed in relation to the immunological status of the patients and the possibilities of active immunotherapy.