title: M-1/M-2 macrophages and the Th1/Th2 paradigm.
abstract: Evidence is provided that macrophages can make M-1 or M-2 responses. The concept of M-1/M-2 fomented from observations that macrophages from prototypical Th1 strains (C57BL/6, B10D2) are more easily activated to produce NO with either IFN-gamma or LPS than macrophages from Th2 strains (BALB/c, DBA/2). In marked contrast, LPS stimulates Th2, but not Th1, macrophages to increase arginine metabolism to ornithine. Thus, M-1/M-2 does not simply describe activated or unactivated macrophages, but cells expressing distinct metabolic programs. Because NO inhibits cell division, while ornithine can stimulate cell division (via polyamines), these results also indicate that M-1 and M-2 responses can influence inflammatory reactions in opposite ways. Macrophage TGF-beta1, which inhibits inducible NO synthase and stimulates arginase, appears to play an important role in regulating the balance between M-1 and M-2. M-1/M-2 phenotypes are independent of T or B lymphocytes because C57BL/6 and BALB/c NUDE or SCID macrophages also exhibit M-1/M-2. Indeed, M-1/M-2 proclivities are magnified in NUDE and SCID mice. Finally, C57BL/6 SCID macrophages cause CB6F1 lymphocytes to increase IFN-gamma production, while BALB/c SCID macrophages increase TGF-beta production. Together, the results indicate that M-1- or M-2-dominant macrophage responses can influence whether Th1/Th2 or other types of inflammatory responses occur.
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis 55455, USA. mills002@tc.umn.edu
authors.forename: C D
authors.initials: CD
authors.lastname: Mills
authors.forename: K
authors.initials: K
authors.lastname: Kincaid
authors.forename: J M
authors.initials: JM
authors.lastname: Alt
authors.forename: M J
authors.initials: MJ
authors.lastname: Heilman
authors.forename: A M
authors.initials: AM
authors.lastname: Hill
mesh_terms: D000818:Animals; D001120:Arginine / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D008262:Macrophage Activation; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008819:Mice, Nude; D016513:Mice, SCID; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D013045:Species Specificity; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018417:Th1 Cells / Q000378:metabolism*; D018418:Th2 Cells / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000502:physiology
chemical_list: D016207:Cytokines; D016212:Transforming Growth Factor beta; D009569:Nitric Oxide; D001120:Arginine