34 Phagocyte collaboration for the control of Pseudomonas aeruginosa.

Pseudomonas aeruginosa (PA) is an opportunistic pathogen that causes infections in patients with compromised immunity. Several previous studies are animal based, but we have established a human neutrophil/macrophage PA infection model to investigate phagocyte collaboration in PA control. Objective i. to investigate the ability of human macrophage-neutrophil co-cultures to control Pseudomonas growth, promote inflammation and cause tissue damage, and ii. to determine how the presence of pro-inflammatory cytokines such as IFN-γ and IL-17A affect the outcome of the infection of macrophage-neutrophils co-cultures with PA. Methods A robust procedure has been established where, neutrophils or macrophages or both are infected with PA with or without cytokines under opsonic and or non-opsonic conditions, and the samples analysed for bacterial colony forming units (CFU) or Flow cytometry. Results The findings so far indicate: 1. macrophages have a minor effect on the control of PA but coordinate the immune response to PA infection; 2. phagocytosis of PA by neutrophils under non-opsonic conditions depends on cell density; 3. as expected, serum enhances neutrophil-mediated killing of PA; 4. IL-17A enhances neutrophil-mediated killing of PA under opsonic conditions and 5. neutrophils synergise with macrophages in clearing PA infection. Conclusion 1. Macrophages coordinate the immune response to PA by producing a number of cytokines. 2. Neutrophil control of PA infection is enhanced by human complement. 3. The cytokine IL-17A enhances the ability of human neutrophils to control PA infection. 4. Neutrophils and macrophages collaborate in clearing PA infections. [ABSTRACT FROM AUTHOR]