Abstract
Bronchoalveolar washings (BAW) were obtained from rats primarily infected with N. brasiliensis during the early infection stage that coincides with the lung passage of the parasite and the recruitment of inflammatory cells. BAW were tested for IL-1, IL-6 and tumour necrosis factor (TNF) activities. We found that IL-1 production occurred only on day 1 post infection and ceased thereafter. IL-6 activity was present as from day 1 with a maximum on day 3 post infection and then returned to its normal levels on day 5 post infection. TNF activity was not recovered in BAW at any time of the early infection. Results obtained from the in vitro culture of BAW-adherent cells demonstrated that on day 1 post infection IL-1, but also large amounts of TNF were produced spontaneously, whereas IL-6 was continuously released. Bacterial lipopolysaccharide (LPS) stimulation of the cell culture resulted in an amplification of the cytokine production. Our results suggest that pulmonary cytokines detected in BAW were at least in part produced by alveolar macrophages. Furthermore, the kinetics of IL-1, TNF and IL-6 production show that these monokines are induced at different times during the course of infection, suggesting that cytokine production may follow different regulation patterns during the early phase of N. brasiliensis infection.