The effects of recombinant bacteria-derived bovine interferon-alpha I1 (rBoIFN-alpha I1) and -gamma (rBoIFN-gamma) on some in vitro immune functions of bovine intestinal leukocytes were studied. The proliferative response of intraepithelial leukocytes (IEL) to concanavalin A (Con A) was significantly inhibited by the addition of 5-1,000 U/ml of either IFN type. In contrast, addition of rBoIFN-alpha I1 to lamina propria leukocytes (LPL) from the same animal, showed significant inhibition only above 500 U/ml, whereas rBoIFN-gamma revealed significant enhancement when added as low as 50 U/ml. The concentration of mitogen and the time of incubation were both critical factors in determining the outcome of IFN-leukocyte interactions. While both IFN types could inhibit DNA synthesis of both leukocyte cultures at suboptimal (0.5 microgram/ml) Con A concentration throughout the time of incubation, their modulatory activities varied significantly at optimal (5.0 micrograms/ml) and supraoptimal (50.0 micrograms/ml) Con A concentrations. Preexposure of cells to IFNs or prestimulation with Con A did not significantly change the kinetics of IFNs with both leukocyte cultures. Pretreatment of leukocyte cultures with either IFN type for 18 h significantly enhanced the expression of MHC surface antigens. These data demonstrate that purified IFNs produced by recombinant DNA technology can significantly alter some in vitro immune functions of cells other than circulating leukocytes and that different IFNs have different capabilities to alter leukocyte functions.
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