In contrast to IL-5 protein expression, IL-5 gene expression (mRNA levels) in homogenates of infected lungs, while paralleling the kinetics of release of this cytokine into the BAL fluid early during infection (Figure 1B), IL-5 transcripts remained readily detectable beyond 8 d.p.i. in spite of the absence of detectable IL-5 protein in the BAL at this time. This evidence concerns the gene IL5 and infection.