TGFB1 and infection: Previous studies have identified distinct populations of circulating neutrophils (N1 and N2) present in the peripheral blood.37,38 TGF-β can drive neutrophils to convert neutrophils to the N2 phenotype (a protumor phenotype similar to M2 macrophages),40 and chronic exposure to nicotine also skews neutrophils toward the N2 phenotype.2 Our data showed that N2 neutrophils dramatically accumulated in the lungs of tumor-bearing mice after chronic PAO1 infection.