Effect of azathioprine on the early stages of human lymphocyte activation.

The effect of azathioprine preincubation on the early stages of mitogenic stimulation of human blood lymphocytes and on spontaneous cell proliferation in vitro was investigated. This effect was measured by the method of 3H-thymidine incorporation in microcultures. The experiments demonstrated: decrease of suppression of lymphocyte stimulation by PHA in cultures preincubated with azathioprine and non restimulated after drug removal, significant reduction of inhibition of lymphocyte stimulation in cultures preincubated with azathioprine and restimulated by PHA after drug removal, a tendency to stimulate spontaneous proliferation in nonstimulated lymphocyte cultures preincubated with AZ and cultured in the absence of the drug, interference of PHA stimulation with the induction of suppression by azathioprine: stimulated lymphocytes are more sensitive to the suppressive effect of AZ, even in the early phase of cell proliferation.