In vitro changes in cell mediated immunity following tuberculin skin testing in humans.

Tuberculin skin testing with purified protein derivative (PPD) was found to induce alterations of in vitro measures of cell mediated immunity. T lymphopenia with proportionate decreases of TM and TG cell numbers were observed two days after skin testing. A relative augmentation of TM cells was demonstrated after one week. Peripheral blood mononuclear cells from negative skin responders had normal in vitro reactivity to PPD stimulation suggesting a cutaneous abberation in these individuals. Macrophage dependent depressed PHA reactivity of mononuclear cells was demonstrated two days after skin testing. No change in natural killer cell cytotoxicity was observed. Cytotoxicity was positively correlated to the number of TG cells in the assay.