Diffusible signal to murine alveolar macrophages from lipopolysaccharide- and Escherichia coli-stimulated lung Type II epithelial cells.

OBJECTIVE AND
DESIGN: To demonstrate a diffusible intercellular macrophage activation factor secreted by Type II alveolar epithelial cells (AECs) in transwell co-cultures. MATERIALS: T(7), our Type II conditionally immortalized AEC line; MH-S, an alveolar macrophage cell line; Lipopolysaccharide (LPS) or uv-killed Escherichia coli (UVEC) for antigen presentation.
METHODS: LPS or UVEC stimulation of T(7) cells in the lower chamber was investigated for ability to activate MH-S cells in the upper chamber, as assayed by nitric oxide production and western blots for inducible nitric oxide synthase-2.
RESULTS: Both transwell and UVEC-conditioned medium experiments showed secretion of an MH-S activation factor by T(7) cells. Many common inflammatory cytokines were ruled out as this immunoactivator.
CONCLUSION: Demonstration of a diffusible activation factor produced by Type II AECs supports their potential role as first responders of innate immunity in the lung.