No 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.

No abstract

To determine the relative contributions of respiratory burst–derived reactive oxygen intermediates (ROI) versus reactive nitrogen intermediates (RNI) to macrophage-mediated intracellular host defense, mice genetically deficient in these mechanisms were challenged with Leishmania donovani, a protozoan that selectively parasitizes visceral tissue macrophages. During the early stage of liver infection at wk 2, both respiratory burst–deficient gp91phox −/− (X-linked chronic granulomatous disease [X-CGD]) mice and inducible nitric oxide synthase (iNOS) knockout (KO) mice displayed comparably increased susceptibility. Thereafter, infection was unrestrained in mice lacking iNOS but was fully controlled in X-CGD mice. Mononuclear cell influx into infected liver foci in X-CGD and iNOS KO mice was also overtly impaired at wk 2. However, granuloma assembly in parasitized tissue eventually developed in both hosts but with divergent effects: mature granulomas were functionally active (leishmanicidal) in X-CGD mice but inert in iNOS-deficient animals. These results suggest that (a) ROI and RNI probably act together in the early stage of intracellular infection to regulate both tissue recruitment of mononuclear inflammatory cells and the initial extent of microbial replication, (b) RNI alone are necessary and sufficient for eventual control of visceral infection, and (c) although mature granulomas have traditionally been associated with control of such infections, these structures fail to limit intracellular parasite replication in the absence of iNOS.

Clinical features of 49 episodes of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome were compared with those of 39 episodes in patients with other immunosuppressive diseases. At presentation patients with the syndrome were found to have a longer median duration of symptoms (28 days versus 5 days, p = 0.0001), lower mean respiratory rate (23.4 versus 30, p = 0.005), and higher median room air arterial oxygen tension (69 mm Hg versus 52 mm Hg, p = 0.0002). The survival rate from 1979 to 1983 was similar for the two groups (57% and 50% respectively). Patients with the syndrome had a higher incidence of adverse reactions to trimethoprim-sulfamethoxazole (22 of 34 versus 2 of 17, p = 0.0007). Survivors with the syndrome at initial presentation had a significantly lower respiratory rate, and higher room air arterial oxygen tension, lymphocyte count, and serum albumin level compared to nonsurvivors. Pneumocystis carinii pneumonia presents as a more insidious disease process in patients with the syndrome, and drug therapy in these patients is complicated by frequent adverse reactions.