Hence, the individual variabilities upon infection needs to take into account when judging for the biological relevance of the observed effects in the absence of htrA. In line with these unexpected data derived from livers of infected mice, splenic IFN-γ, IL-6, and TNF-α levels increased only upon ΔhtrA knockout mutant, but not parental WT strain infection when compared to naive controls. This evidence concerns the gene IL6 and infection.