Elevated plasma levels of MMP9 in STAT3-deficient patients (25) and its role in degradation of extracellular matrix during tissue remodeling led us to hypothesize that MMP9 may be differentially expressed in myeloid STAT3-deficient as compared with WT mice during pulmonary staphylococcal infection. This evidence concerns the gene MMP9 and staphylococcal infection.