IFN-gamma potentiates the release of TNF-alpha and MIP-1alpha by alveolar macrophages during allergic reactions.

Viral infections play an important role in the exacerbation of asthma. The production of interferons (IFNs) is well known to limit viral spread, but IFN-gamma can also prime alveolar macrophages to release more inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-1alpha (MIP-1alpha). Given the importance of these cytokines, we have investigated the effect of IFN-gamma on their release by alveolar macrophages during stimulation by immunoglobulin (Ig)E/anti-IgE. Alveolar macrophages from normal or Nippostrongylus brasiliensis-infected rats, the latter having increased numbers of low-affinity receptors for IgE (Fcepsilon RII) on their alveolar macrophages, were treated with IgE for 2 h and stimulated with anti-IgE for 18 h. The increase of TNF-alpha release (153 +/- 48 pg/10(6) cells) by IgE/anti-IgE occurred only with alveolar macrophages from infected rats. The messenger RNA level for TNF-alpha in rat alveolar macrophages was also increased by stimulation with IgE/anti-IgE. Treatment with IFN-gamma prior to stimulation with IgE/anti-IgE showed a time- and concentration-dependent increase of TNF-alpha release. Interestingly, IgE/anti-IgE treatment did not stimulate the release of MIP-1alpha (15 +/- 5 pg/10(6) cells), but IFN-gamma treatment alone and with IgE /anti-IgE significantly increased and potentiated MIP-1alpha release (98 +/- 40 pg/10(6) cells) by alveolar macrophages, respectively. These results suggest that IFN-gamma produced at times such as during viral infections primes alveolar macrophages for enhanced release of inflammatory mediators during allergic reactions, thereby contributing to the inflammatory process.