Effect of alpha 1-acidic glycoprotein in the ascitic fluid of cancer patients on human NK cells: selective suppression of interferon-induced NK activation.

The in vitro effect of C-AGP (pure alpha1-acid glycoprotein from the ascitic fluid of cancer patients) on NK cell cytotoxicity was tested using normal healthy human PBMC. C-AGP had no inhibitory effect on basal NK cell activity. C-AGP selectively suppressed the augmentation of NK cell activity by rIFNalphaA and rIFNgamma, but C-AGP did not prevent the NK activation by rIL-2. NK cells in PBMC treated with C-AGP for 12 h and then washed just once, to remove the C-AGP, fully recovered the ability to respond to rIFNalphaA. However, after the treatment of PBMC with C-AGP for 5 or 6 days, NK cells failed to respond to rIFNalphaA, in spite of washing to remove C-AGP from the cultures. Monocytes were necessary for the suppressive effect of C-AGP on rIFNalphaA activation of NK cells. Indomethacin restored the ability of NK cells to respond to rIFNalphaA in C-AGP-treated PBMC. These results suggest that monocytes are able to selectively suppress the response of NK cells to IFNs in the presence of, or following treatment with C-AGP.