Improvement of Phytohemagglutinin Responsiveness of Lymphocytes from Cancer Patients after Washing in Vitro

Summary

The in vitro response to phytohemagglutinin (PHA) stimulation of the peripheral blood lymphocytes from 23 patients with a variety of metastatic solid-tissue cancers was studied after one washing and again after six washings of the lymphocytes in tissue culture medium. The response of each patient's lymphocytes was compared with that of the lymphocytes from a simultaneously studied normal control individual. After one in vitro washing, it was found that the lymphocytes of 14 of the 23 cancer patients were suppressed in their response to PHA, at at least 1 PHA dosage, as indicated by a proliferative response of less than one-half of that of control lymphocytes (measured by incorporation of [³H]thymidine). These suppressed cancer patients, as a group, had a significantly lower maximal stimulation in response to PHA than the control group (23,673 ± 5,079 cpm versus 89,373 ± 9,725 cpm, p < 0.001), whereas nine nonsuppressed cancer patients did not (74,146 ± 9,471 cpm, p > 0.3). After six in vitro washings, the lymphocytes of 12 of the 14 suppressed cancer patients improved in response to PHA stimulation, at one or more dosages, as defined by an increase in proliferative response of two or more times that of the same cells in response to the same PHA dosage after one washing. By this criterion, the lymphocytes of 2 of 14 controls and 2 of 9 nonsuppressed cancer patients improved in response to PHA after six washings. The improvement in response of the suppressed cancer patient's lymphocytes after six washings, as compared with the controls, was highly significant (p < 0.01). The nonsuppressed cancer patients resembled the controls (p > 0.6). These results suggest that the nonspecific defect in lymphocyte activation noted in certain patients with advanced cancer may be caused by a suppressor substance or substances loosely associated with the lymphocyte cell membrane.