Journal of leukocyte biology
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Although previous studies suggested that tumor necrosis factor alpha (TNF-alpha) was a critical cytokine responsible for the inflammation observed after exposure to endotoxin, other mediators may also play an important role in the regulation of systemic inflammatory responses independent of TNF-alpha. The present study compared the temporal sequence of endotoxin-induced TNF-alpha, interleukin-1 alpha (IL-1 alpha), and interleukin-10 (IL-10) gene expression and cellular localization of cytokine proteins in pulmonary tissue of two strains of mice that have a genetically based differential sensitivity to endotoxin. Lung tissue and plasma were harvested from endotoxin-sensitive C3H/HeN and endotoxin-resistant C3H/HeJ mice at 15 min, 30 min, 1 h, 2 h, 4 h, 6 h, 12 h, and 24 h after intraperitoneal (i.p.) injection of 5 mg/kg endotoxin (Escherichia coli-derived lipopolysaccharide, serotype 0111:B4). ⋯ Quantitation of neutrophil infiltration into pulmonary tissue using immunochemical detection of GR-1, a myeloid differentiation-specific antibody, demonstrated that there was a significantly decreased inflammatory infiltrate in pulmonary tissue isolated from C3H/HeJ mice following endotoxin administration, which correlated with decreased levels of proinflammatory cytokine immunoreactive protein within pulmonary cells. Pulmonary cytokine synthesis and immunoreactive protein production did not directly correlate with either the magnitude or the temporal sequence of increases in plasma cytokine levels, suggesting that systemic levels of cytokines may not accurately reflect the cytokine response within the local tissue milieu. The present observations demonstrate that the differential synthesis and production of immunosuppressive cytokines as well as proinflammatory cytokines may be important variables in the determination of the extent of infiltration of inflammatory cells into the local pulmonary site in response to endotoxin and may significantly contribute to the determination of sensitivity or resistance to endotoxin in this murine model.