Inhibition of human lymphocyte stimulation by steroid hormones: cytokinetic mechanisms.

TL;DRAbstract

The steroid hormones estradiol, progesterone and testosterone, in addition to cortisol, inhibited stimulation of human peripheral blood lymphocytes by phytohaemagglutinin (PHA) and Con A. This effect upon lymphocyte transformation was assayed by three methods: quantitation of [3H]thymidine incorporation into acid precipitable material, microscopic assessment of blastic transformation and determination of the labelling index. Addition of steroid hormones at the initiation of culture resulted in a marked inhibition in all three parameters, which was observed with lower concentrations of cortisol than the other hormones. The inhibition was not attributable to cell death and could be partially reversed by removing hormones from the incubation medium after culture for 48-72 hr. Late addition of steroid hormones, 52 hr after addition of mitogen and 18 hr prior to pulse-labelling with [3H]thymidine, also resulted in reduced [3H]thymidine incorporation, accompanied by a nearly 50% reduction in

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