Compared to the ∼15-fold increase in secreted proMMP-9 that was observed in PPARγVillinCre- mice after infection (Fig. 5F and G), a mere ∼3-fold increase in the levels of secreted proMMP-9 was detected in Lcn2−/− mice after infection, suggesting reduced extracellular stability and possible degradation of MMP-9 protein in the absence of Lcn2 (Fig. 7C and D). Here, MMP9 is linked to infection.