As shown in Fig. 7b, no AZD2014 significant reduction in TNF-α expression was detected by this treatment. These results suggested that F4/80+ cells may contribute to the expression of this cytokine as additional cells to Gr-1+ cells. The current study demonstrated that (1) administration of anti-TNF-α mAb led to shortened survival and

impaired the recruitment of neutrophils in the lungs of mice infected with S. pneumoniae, (2) in a flow cytometric analysis, TNF-α was expressed in Gr-1bright+ and Gr-1dull+ cells at an early stage of infection, (3) the Gr-1bright+ and Gr-1dull+ cells sorted from BALF cells consisted of neutrophils and macrophage-like cells, respectively, (4) the Gr-1dull+ cells expressed CD11c and partially expressed CD11b and MHC class II, but did not express or marginally expressed CD80, (5) the Gr-1dull+ cells were committed to secrete TNF-αin vitro irrespective of stimulation with this bacterium and (6) depletion of Gr-1+ cells

by administration of the specific mAb caused the reduced production of TNF-α in lungs. These results indicated that neutrophils and Gr-1dull+ macrophage-like cells contributed to the synthesis of this cytokine in lungs after infection with ROCK inhibitor S. pneumoniae, which may play an important role in the host defense to this infection. In previous investigations (Romani et al., 1997; Bliss et al., 1999, 2000; Cassatella, 1999; Denkers et al., 2003; Tsuda et al., 2004; Bennouna & Denkers, 2005), it was demonstrated that neutrophils played critical BCKDHA roles in the host defense to infection not only by killing microbial pathogens but also by regulating inflammatory responses through generation of a variety of cytokines and chemokines. These cells were reported to secrete

TNF-α and interleukin-12 (IL-12) after stimulation with lipopolysaccharides and infection with Candida albicans, Staphylococcus aureus and Toxoplasma gondii (Cassatella, 1995, 1999; Romani et al., 1997; Bliss et al., 1999, 2000; Denkers et al., 2003; Tsuda et al., 2004; Bennouna & Denkers, 2005). In the current study, we identified these cells as the cellular source of early production of TNF-α in lungs after infection with S. pneumoniae. Neutrophils intracellularly expressing this cytokine appeared and increased in BALF at as rapid a stage as 1.5–12 h post-infection. TNF-α is known to be secreted through the cell membrane of neutrophils after cleavage of its precursor form prestored in the cytosolic compartments (Black et al., 1997; Black, 2002; Bennouna & Denkers, 2005), raising the possibility that an increase in the intracellular expression of this cytokine does not necessarily mean its secretion as an active form at the infected tissues. Here, we have not confirmed the secretion of TNF-α from the Gr-1bright+ neutrophils sorted at 24 h postinfection in the in vitro cultures.