Splenic and lung response to nonlethal systemic Aspergillus fumigatus infection in C57BL/6 mice

In this study, we investigated splenic and lung cell responses to nonlethal systemic Aspergillus fumigatus infection in mice. Apart from basic indices of spleen and lung cell activity, IL-17 expression by cells from both tissues was determined and compared to the expression of IFN-gamma and IL-4. Progressive decrease in tissue fungal burden correlated with increased spleen and lung cell activity. Increased IL-17 message was noted in spleen cells at all time points (3, 7 and 15 days post-infection; p.i.), while a modest increase in IFN-gamma mRNA expression was noted at day 3 p.i. Increased cytokine production at days 3 and 7 (IL-17) and throughout the experimental period (IFN-gamma) was found. In contrast, spleen cell IL-4 expression was considerably lower during infection, resulting in high IFN-gamma/IL-4 and IL-17/IL-4 ratios in the spleen. Pro-inflammatory cytokine response was observed in the lungs as well, but primarily as the result of increased production of IFN-gamma by lung cells in response to challenge with conidia and the absence of change in IL-4 response. Increased activity of cells from both tissues, as well as the pattern of cytokine production, created an optimal pro-inflammatory milieu for fungal eradication.