Cutting edge: Outer membrane protein A (OmpA) binds to and activates humanmacrophages

Outer membrane protein (Omp)A is highly represented and conserved in the En terobacteriaceae family. Using a recombinant OmpA From Klehsiella pneumonia e (P40), we have analyzed the interaction between OmpA and macrophages. We report that Alexa(488)-labeled P40 binds (at 4 degreesC) to murine and huma n macrophages in a dose-dependent manner and is rapidly internalized (at 37 degreesC), No binding or internalization of the Alexa(488)-labeled glycoph orin A control protein is observed under the same conditions, Furthermore, P40 up-regulates the production of IL-1 beta, IL-8, IL-10, IL-12, and TNF-a lpha by human macrophages and of NO by the RAW 264.7 murine macrophage cell line, P40 also synergizes with IFN-gamma and suboptimal concentrations of LPS to up-regulate the production of these mediators. In conclusion, P40 bi nds to and activates macrophages, These data suggest that recognition of Om pA by macrophages may be an initiating event in the antibacterial host resp onse.