Inhibition of mitogen-induced human lymphocyte responsiveness by polymixin antibiotics

Polymixin antibiotics, polymixin B and polymixin E (colistin) inhibited the mitogen-induced lymphoproliferative response of human lymphocytes. Inhibition of the lymphocyte response to PHA, PWM and Con A was evident at a low concentration of 1 U/ml of antibiotics. Lymphocytes in which the signals for proliferation had occurred were similarly prevented from proliferating. The effects were not due to cell death (toxicity). Since polymixin concentrations at which inhibition of lymphocyte proliferation was observed are employed in tissue culture medium and are also attained in plasma of patients, the results suggest that the use of the antibiotics in lymphocyte cultures limits lymphocyte responsiveness and that patients receiving polymixin antibiotics may experience a state of immunosuppression