Identification of interferon-gamma as the lymphokine that activates human macrophage oxidative metabolism and antimicrobial activity.

Abstract

Human blood mononuclear leukocytes stimulated with toxoplasma antigen, concanavalin A, mezerein plus lentil lectin, or staphylococcal enterotoxin A secreted a factor (macrophage-activating factor, or MAF) that enhanced the capacity of human macrophages to release H2O2 and to kill toxoplasmas. The same lymphoid supernatants contained IFN gamma but not IFN alpha or IFN beta. The MAF activity of six of seven unfractionated supernatants was completely eliminated by a monoclonal antibody that neutralizes IFN gamma, and MAF in the remaining supernatant was almost completely neutralized. Native IFN gamma partially purified by two independent protocols to specific activities of 1 X 10(6) and 10(7) U/mg protein was enriched in MAF activity at least as much as in antiviral activity. The capacity of macrophages to secrete H2O2 after incubation in partially purified native IFN gamma (mean peak stimulation, 8.8-fold) was greater than with unpurified lymphokines (3.8-fold) and sometimes equaled or exceeded the capacity of freshly harvested monocytes. The MAF activity of the partially purified native IFN gamma preparations was abolished by monoclonal anti-IFN gamma. Finally, IFN gamma of greater than 99% estimated purity was isolated (at Genentech, Inc.) from bacteria transformed with the cloned human gene for this lymphokine. Recombinant IFN gamma had potent MAF activity, stimulating the peroxide-releasing capacity of macrophages an average of 19.8-fold at peak response and enhancing their ability to kill toxoplasmas from 2.6 +/- 1.3% for untreated cells to 54 +/- 0.4% for treated cells. Attainment of 50% of the maximal elevation in peroxide-releasing capacity required a geometric mean concentration of 0.1 antiviral U/ml of recombinant IFN gamma, which is estimated to be approximately 6 picomolar for this preparation. Peroxide secretory capacity and toxoplasmacidal activity of macrophages peaked 2-4 d after exposure to IFN gamma. Peroxide-secretory capacity remained elevated during at least 6 d of continuous exposure, but the effect of IFN gamma was reversed within about 3 d of its removal. Activation was usually but not invariably accompanied by characteristic changes in cell morphology. Thus, IFN gamma activates human macrophage oxidative metabolism and antimicrobial activity, and appeared to be the only factor consistently capable of doing so in the diverse LK preparations tested.

Successful treatment of colon cancer in rats with recombinant interferon-gamma

“…The finding that rRIFN-y had no effect in vitro, at least not during the culture period of 3 days employed in the current study, suggests that the in vivo effect was indirect; possibly mediated by an activated immune system combined with an enhanced susceptibility of the tumour (Ball et al, 1986;Feinman et al, 1986). This putative involvement of the immune system may be an explanation for the discrepancy between the effect of rRIFNv (Nathan et al, 1983) and may have contributed to the low number of liver metastases and the improved survival found in the current experiments.…”

“…In addition, a number of immunological functions influenced by IFN-y may synergize with this direct cytotoxic action. It has been demonstrated that IFN-y can enhance monocyte cytotoxicity (Kleinerman et al, 1985), macrophage activity (Nathan et al, 1983) and natural killer (NK) cell activity (Weigent et al, 1983). Furthermore, IFN-y can enhance the expression of surface antigens on tumour cells (Pfizenmaier et al, 1985) and on cells of the immune system, i.e.…”

Down-regulation of MHC class II molecules and inability to up-regulate class I molecules in murine macrophages after infection withToxoplasma gondii

“…* Significantly different compared with the non-infected control cultures (Student's t-test). down-regulated by parasitic infection, thus abrogating IFN-gmediated activation of macrophages by CD4 þ and CD8 þ T lymphocytes for anti-microbicidal activity against intracellular parasites [29]. Additionally, lysis of T. gondii-infected APC by cytotoxic CD4 þ [30] and CD8 þ [31] T lymphocytes may also be avoided by decreasing the antigen-presenting capacity of infected macrophages, while cytolytic activity in the absence of MHC restriction as described for a Toxoplasma-specific CD8 þ T cell clone [32] would not be affected.…”

In-vitro toxoplasmacidal activity of cationic electron carriers

“…Activated macrophages are able to kill Tox. gondii in vitro, and this killing seems to be associated with the ability of the macrophages to release reactive oxygen intermediates (ROI) such as superoxide anion, hydrogen peroxide and hydroxyl radical (Nathan et al, 1983;Murray, Spitalny & Nathan, 1985). Studies have shown that cationic electron carriers, which are thought to undergo redox-cycling and generating superoxide anion and hydrogen peroxide (Hassan & Fridovich, 1979), were able to inhibit intracellular Trypanosoma cruzi and Leishmania spp.…”