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Outer membrane protein A (OmpA) binds to and activates human macrophages
C Soulas1, T Baussant, J P Aubry
1Centre d'Immunologie Pierre Fabre, Saint-Julien en Genevois, France.
Abstract:
Outer membrane protein (Omp)A is highly represented and conserved in the Enterobacteriaceae family. Using a recombinant OmpA from Klebsiella pneumoniae (P40), we have analyzed the interaction between OmpA and macrophages. We report that Alexa488-labeled P40 binds (at 4 degrees C) to murine and human macrophages in a dose-dependent manner and is rapidly internalized (at 37 degrees C). No binding or internalization of the Alexa488-labeled glycophorin A control protein is observed under the same conditions. Furthermore, P40 up-regulates the production of IL-1beta, IL-8, IL-10, IL-12, and TNF-alpha 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 binds to and activates macrophages. These data suggest that recognition of OmpA by macrophages may be an initiating event in the antibacterial host response.
Insights
Outer membrane protein A (OmpA) from Klebsiella pneumoniae binds to and activates macrophages. This interaction may initiate the host
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Outer membrane protein A (OmpA) is a conserved and abundant protein in Enterobacteriaceae.
- Understanding OmpA's interaction with host immune cells is crucial for deciphering bacterial pathogenesis and host defense mechanisms.
Purpose of the Study:
- To investigate the interaction between Outer membrane protein A (OmpA) from Klebsiella pneumoniae and macrophages.
- To determine if OmpA binding and internalization by macrophages trigger an immune response.
Main Methods:
- Utilized Alexa488-labeled recombinant OmpA (P40) from Klebsiella pneumoniae.
- Assessed P40 binding and internalization by murine and human macrophages using flow cytometry at different temperatures.
- Measured cytokine (IL-1β, IL-8, IL-10, IL-12, TNF-α) and nitric oxide (NO) production by macrophages.
Main Results:
- Alexa488-labeled P40 demonstrated dose-dependent binding and rapid internalization by macrophages.
- No binding or internalization was observed for the control protein, glycophorin A.
- P40 significantly upregulated the production of key inflammatory cytokines and nitric oxide in macrophages, and synergized with IFN-γ and LPS.
Conclusions:
- Outer membrane protein A (OmpA) from Klebsiella pneumoniae binds to and activates macrophages.
- Macrophage recognition of OmpA may represent an initial step in the host's antibacterial immune response.