title: Neutrophils, not monocyte/macrophages, are the major splenic source of postburn IL-10.
abstract: Burn induces myeloid-derived suppressor cells (MDSCs), a heterogeneous population of immature polymorphonuclear neutrophils (PMNs) and monocytes, which protect against infection. Previous work from our laboratory demonstrated that inflammatory monocytes (iMos) were the major MDSC source of TNF-α in the postburn spleen, and we hypothesized that they were also the major source of postburn IL-10. To test this hypothesis, we examined cytokine production by postburn CCR2 knockout (KO) mice, which have fewer iMos than burn wild-type (WT) splenocytes, but equal numbers of PMNs and F4/80 macrophages. Using cell sorting and/or intracellular cytokine techniques, we examined IL-10 production by postburn PMNs and iMos. Finally, we compared IL-10 production by postburn PMNs and iMos with culture-derived MDSCs. Splenocytes from postburn CCR2 KO mice produced less IL-6 and TNF-α than WT burn splenocytes in response to LPS, but KO and WT burn splenocytes produced equal amounts of IL-10 in response to peptidoglycan. Depletion of PMNs from postburn splenocytes led to reductions in IL-10 and increases in IL-6 and TNF-α in response to peptidoglycan, but not in response to LPS. Sorting or intracellular cytokine techniques gave consistent results: Burn PMNs made more IL-10 than sham PMNs and also more IL-10 than burn or sham iMos. Polymorphonuclear neutrophil and iMos subpopulations from culture-derived MDSCs produced the same cytokine profiles in response to LPS and peptidoglycan as did the PMNs and iMos from postburn spleens: PMNs made IL-10, whereas iMos made IL-6. Finally, LPS-induced mortality of burn mice was made worse by anti-Gr-1 depletion of all PMNs and 66% of iMos from burn mice. This suggests that PMNs play a primarily anti-inflammatory role in vitro and in vivo.
authors.affiliation: Department of Research, Shriners Hospital for Children; and †Department of Surgery, University of Cincinnati, Cincinnati, OH 45209, USA. gnoel@shrinenet.org
authors.forename: Greg
authors.initials: G
authors.lastname: Noel
authors.forename: Quan
authors.initials: Q
authors.lastname: Wang
authors.forename: Sandy
authors.initials: S
authors.lastname: Schwemberger
authors.forename: Craig
authors.initials: C
authors.lastname: Hanson
authors.forename: Nick
authors.initials: N
authors.lastname: Giacalone
authors.forename: Lauren
authors.initials: L
authors.lastname: Haar
authors.forename: Cora K
authors.initials: CK
authors.lastname: Ogle
mesh_terms: D000818:Animals; D002056:Burns / Q000276:immunology* / Q000503:physiopathology; D005434:Flow Cytometry; D016753:Interleukin-10 / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D022423:Myeloid Cells / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D054390:Receptors, CCR2 / Q000235:genetics / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C515335:Ccr2 protein, mouse; D054390:Receptors, CCR2; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10