CYTOKINE MODULATABLE SIGNALING THROUGH MACROPHAGE HLA CLASS-II .1. IFN-GAMMA UP-REGULATES THE EFFICIENCY OF CA2-DP( MOBILIZATION IN RESPONSE TO LIGATION OF MACROPHAGE HLA)

The human macrophage line 2MAC, established recently from peripheral b lood, expresses a number of lineage-specific markers as well as a broa d array of intercellular adhesion molecules, including high levels of HLA class I and class II. We have presented evidence elsewhere that 2M AC can be productively applied to the study of signal transduction thr ough macrophage HLA class II. Namely, we showed that ligation of 2MAC HLA class II, but not HLA class I, by monoclonal antibody (mAb) elicit s an increase in free cytoplasmic Ca2+ concentration [Ca2+](i). Moreov er, this Ca2+ flux appears to be functionally relevant: ligation of HL A-DR, but not HLA class I, by mAb results in the Ca2+ mobilization-dep endent induction of tissue factor, the high-affinity cellular receptor for factor VII/VIIa. Here we show that 2MAC is uniquely valuable for addressing the efficiency of signal transduction through HLA class II. Namely, we show here that prior culture of 2MAC cells with interferon -gamma (IFN-gamma) profoundly upregulates subsequent Ca2+ mobilization in response to ligation of HLA-DP in the absence of increased cell su rface HLA-DP expression. Because IFN-gamma has no effect on 2MAC HLA-D P expression, IFN-gamma must upregulate Ca2+ mobilization by increasin g the efficiency of signal transduction through HLA class II (HLA-DP), by targeting some other component of the macrophage HLA class II sign alling pathway.