ALVEOLAR MACROPHAGES FROM PATIENTS WITH AIDS AND AIDS-RELATED COMPLEX CONSTITUTIVELY SYNTHESIZE AND RELEASE TUMOR-NECROSIS-FACTOR-ALPHA

To verify the hypothesis that alveolar macrophages (AMs) from patients infected with HIV-1 could synthesize and release TNF-alpha, AMs recovered from the BAL fluid of 11 patients with seropositive HIV-1 (six with AIDS and five with ARC) were tested in vitro for their ability to destroy TNF-alpha-susceptible targets. Furthermore, the presence of TNF-alpha was assessed in AM-conditioned supernatants on the basis of their cytotoxic activity and by using an immunoenzymatic test and immunoblotting. Transcription of the TNF-alpha-gene in AMs was also studied by means of the Northern blot analysis. AMs freshly recovered from patients infected with HIV-1 exhibited high levels of cell-mediated cytotoxicity against U937 targets, and the addition of a polyclonal anti-TNF-alpha-antibody resulted in a significant inhibition of the target lysis. Cell-free supernatants conditioned by unstimulated AMs exerted high levels of cytotoxic activity against TNF-alpha-sensitive targets, whereas duplicate, neutralization experiments performed in the presence of an anti-TNF-alpha-antibody proved that the observed cytotoxic activity was mostly mediated by TNF-alpha. The presence of high amounts of TNF-alpha in the conditioned media was confirmed by the immunoenzymatic test. In addition, the immunoblot analysis showed that the TNF-alpha released by AMs has a M(r) 17,000 band, identical to a standard preparation of recombinant TNF-alpha. The Northern blot demonstrated that unstimulated AMs express detectable levels of mRNA transcripts for TNF-alpha. Taken together, our data support the concept that AMs from patients with HIV-1 infection constitutively release TNF-alpha. Because normal human AMs do not express detectable levels of mRNA for TNF-alpha or release this cytokine, the hypothesis is formulated that in the lung of patients with AIDS, AMs, either by a direct effect of HIV-1 infection or as a consequence of the pulmonary opportunistic infections, are triggered to synthesize TNF-alpha. This in situ overproduction might play a role in the pathogenesis of AIDS-related pulmonary complications.