Constitutive expression of mRNAs for GROalpha, GRObeta, GROgamma, and MCP-1, belonging to the chemokine family of 8-10 kD cytokines with chemotactic properties for granulocytes and monocytes, has been identified in freshly isolated human nasal and bronchial epithelium, and in bronchoalveolar macrophages (AM). Using a semiquantitative RT/PCR technique, the authors found constitutive expression of IL-8 > GROalpha > GROgamma and MCP1, but not GRObeta, in airway epithelial cells. In comparison, AM expressed less GROalpha, similar levels of IL-8, but at least 10 times more GROgamma and MCP1 than the epithelial cells. In addition, AM expressed GRObeta mRNA. Upon reverse transcription, chemokine mRNAs yielded 0.5 to 30 cDNA molecules/cell, depending on the chemokine and cell type. Modulation of chemokine expression by TNFalpha(10 ng/ml) or endotoxin (LPS, 100 ng/ml) exposure was studied in primary nasal epithelial cell and alveolar macrophage cultures. In epithelial cells, LPS did not induce chemokine expression but GROalpha and IL-8 were upregulated approximately 100 fold by TNFalpha; GROgamma expression was elevated 5-10 fold while MCP-1 was increased approximately 40 fold. In AM cultures, all three GROs were strongly induced by LPS with peak mRNA expression 24 h after stimulation. MCP1 mRNA expression, on the other hand, was not induced by LPS. GRO protein was present in supernatants of stimulated epithelial cells and AM while MCP-1 protein was not detectable by western blot anlaysis with a sensitivity limit of 20 ng/ml MCP-1. Together these data emphasize the potential importance of the chemokine family of polypeptides in airway inflammation, as well as the importance of both airway epithelium and AM in these processes.