title: IL-33 and M2a alveolar macrophages promote lung defense against the atypical fungal pathogen Pneumocystis murina.
abstract: We have recently reported that mice deficient in the myeloid Src-family tyrosine kinases Hck, Fgr, and Lyn (Src triple knockout [TKO]) had augmented innate lung clearance of Pneumocystis murina that correlated with a higher ability of alveolar macrophages (AMs) from these mice to kill P. murina. In this article, we show that despite possessing enhanced killing, AMs from naive Src TKO mice did not demonstrate enhanced inflammatory responses to P. murina. We subsequently discovered that both AMs and lungs from P. murina-infected Src TKO mice expressed significantly greater levels of the M2a markers RELM-α and Arg1, and the M2a-associated chemokines CCL17 and CCL22 than did wild-type mice. IL-4 and IL-13, the primary cytokines that promote M2a polarization, were not differentially produced in the lungs between wild-type and Src TKO mice. P. murina infection in Src TKO mice resulted in enhanced lung production of the novel IL-1 family cytokine IL-33. Immunohistochemical analysis of IL-33 in lung tissue revealed localization predominantly in the nucleus of alveolar epithelial cells. We further demonstrate that experimental polarization of naive AMs to M2a resulted in more efficient killing of P. murina compared with untreated AMs, which was further enhanced by the addition of IL-33. Administration of IL-33 to C57BL/6 mice increased lung RELM-α and CCL17 levels, and enhanced clearance of P. murina, despite having no effect on the cellular composition of the lungs. Collectively, these results indicate that M2a AMs are potent effector cells against P. murina. Furthermore, enhancing M2a polarization may be an adjunctive therapy for the treatment of Pneumocystis.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Nelson
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Christmann
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Werner
authors.forename: Allison E
authors.initials: AE
authors.lastname: Metz
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Trevor
authors.forename: Clifford A
authors.initials: CA
authors.lastname: Lowell
authors.forename: Chad
authors.initials: C
authors.lastname: Steele
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D007113:Immunity, Innate / Q000235:genetics; D007249:Inflammation / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D000067596:Interleukin-33; D007378:Interleukins / Q000096:biosynthesis / Q000502:physiology*; D008262:Macrophage Activation / Q000235:genetics / Q000276:immunology; D016676:Macrophages, Alveolar / Q000201:enzymology / Q000276:immunology* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000235:genetics / Q000276:immunology; D011010:Pneumocystis / Q000254:growth & development / Q000276:immunology* / Q000472:pathogenicity*; D011020:Pneumonia, Pneumocystis / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control*; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000502:physiology; D051572:Proto-Oncogene Proteins c-hck / Q000172:deficiency / Q000502:physiology; D019061:src-Family Kinases / Q000172:deficiency / Q000502:physiology
chemical_list: C506535:Il33 protein, mouse; D000067596:Interleukin-33; D007378:Interleukins; D011518:Proto-Oncogene Proteins; C496632:Hck protein, mouse; D051572:Proto-Oncogene Proteins c-hck; C060902:lyn protein-tyrosine kinase; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases