ACTIVATION OF HUMAN BLOOD-LYMPHOCYTES BY HOUSE-DUST MITE PROTEIN AND MYCOBACTERIUM-TUBERCULOSIS PURIFIED PROTEIN DERIVATIVE - EFFECTS OF INTERFERON-GAMMA, INTERLEUKIN-4, DEXAMETHASONE AND CYCLOSPORINE-A

Peripheral blood mononuclear cells (PBMC) from nonatopic donors sensit ive to Mycobacterium tuberculosis purified protein derivative (PPD) an d from atopic donors sensitive to PPD and house dust mite antigen (HDM ), were stimulated in vitro to proliferate in response to exogenous IL -2. In the presence of exogenous IFN-gamma, the response of cells from atopic donors to PPD was either unaffected or slightly enhanced, wher eas the response to HDM was inhibited in a dose-dependent manner. The response of cells from nonatopic donors to PPD remained unchanged or w as only slightly inhibited and this was not dose-dependent. Exogenous IL-4 did not reverse the inhibitory effects of IFN-gamma and a neutral izing antibody to IL-4 did not inhibit the proliferative response of c ells to HDM and IL-2. Dexamethasone inhibited the IL-2-mediated respon se of cells from atopic donors stimulated with HDM, whereas the IL-2-m ediated response of cells induced by PPD was either unchanged or stimu lated by dexamethasone. Cyclosporin A inhibited the response of cells to both HDM and PPD. These results suggest that IFN-gamma can exert a selective effect on the response of T lymphocytes to different antigen s and that it is possible to identify compounds able to regulate this activity.