Interferon-γ is a critical factor in the activation of several mononuclear phagocyte effector and immunoregulatory properties. However, it remains uncertain if IFN-γ is capable of concurrent activation of both functions in the same cell population. Plastic adherent mononuclear cells (80-98% MN by cytochemical criteria) were cultivated in the absence or presence of recombinant interferon-γ (rIFN-γ, 0.1-100 U/ml) for 48 hr. MN surface DR antigen was assessed by flow cytometry (EPICS V) after staining with monoclonal antibodies OKIa1 or L243. Exposure to rIFN-γ (100 U/ml) increased MN surface DR antigen (mean fluorescence intensity) by 80 ± 20% (P <0.01) and 121 ± 52% (P <0.001), respectively, compared to untreated cells. The increase in DR antigen was maximal at 100 U/ml, dependent on protein and RNA synthesis and blocked by agents that increase cAMP levels. IL-1 activity was determined in the mouse thymocyte assay; rIFN-γ (100 U/ml) increased IL-1 activity in the supernatants of MN cultured in medium alone from 0.5 ± 0.2 to 7.8 ± 4.7 U/ml (P <0.05), and lipopolysaccharide-stimulated MN from 20.4 ± 19.1 to 71.7 ± 38.9 U/ml (P <0.05). Following rIFN-γ exposure, MN stimulation of the AMLR was increased at 6 days (29,269 ± 5224 vs 13,252 ± 4938 cpm, P <0.01). Spontaneous cytotoxicity (SC) and antibody-dependent cell cytotoxicity (ADCC) were studied in a 51Cr release microculture assay using the human lymphoblastoid cell line CCRF-CEM as target. SC by MN increased linearly as a function of log[rIFN-γ] for effector: target (E:T) ratios of 5:1 (r = 0.95, P <0.01) and 10:1 (r = 0.99, P <0.01). ADCC by MN increased following rIFN-γ exposure (100 U/ml) at E:T ratios of 5:1 (22 ± 13 to 31 ± 4%, P <0.025) and 10:1 (31 ± 4 to 38 ± 4%, P <0.01). Thus, rIFN-γ not only activates MN effector function, but has concurrent stimulatory effects on multiple MN properties critical to immunoregulation.
ASJC Scopus subject areas
- Cell Biology