title: Alloantigen-reactive Th1 development in IL-12-deficient mice.
abstract: IL-12p70, a 70- to 75-kDa heterodimer consisting of disulfide-bonded 35-kDa (p35) and 40-kDa (p40) subunits, enhances Th1 development primarily by its ability to induce IFN-gamma production by NK and Th1 cells. Although homodimers of the p40 subunit of IL-12 are potent IL-12 receptor antagonists in some systems, we have reported that p40 homodimer may accentuate alloreactive CD8+ Th1 function. To test the role of endogenously produced p40 in alloimmunity, Th1 development was assessed in either IL-12 p35 knockout (p35-/-) mice, the cells of which are capable of secreting p40, or p40 knockout (p40-/-) mice. Compared with IL-12 wild-type controls, splenocytes obtained from both p35-/- and p40-/- mice produced markedly less IFN-gamma after in vitro stimulation with Con A or alloantigens. Interestingly, in vivo-sensitized Th1 were detected in both p35-/- and p40-/- cardiac allograft recipients. However, in vivo Th1 development was enhanced in p35-/- recipients compared with p40-/- animals, suggesting that endogenous p40 produced in p35-/- mice may stimulate alloreactive Th1. Indeed, neutralizing endogenous p40 with anti-IL-12 p40 mAb reduced Th1 development in p35-/- allograft recipients to that seen in p40-/- mice. To determine whether Th1 development that occurred in the absence of IL-12p70 and p40 required IFN-gamma, p40-/- allograft recipients were treated with anti-IFN-gamma mAb. Neutralizing IFN-gamma did not inhibit in vivo Th1 development in p40-/- recipients and resulted in a unique pathology of rejection characterized by vascular thromboses. Collectively, these data suggest that 1) endogenous p40 may substitute for IL-12p70 in alloantigen-specific Th1 sensitization in vivo and 2) in vivo alloreactive Th1 development may occur independent of IL-12 and IFN-gamma, suggesting an alternate Th1-sensitizing pathway.
authors.affiliation: Department of Surgery, University of Michigan School of Medicine, Ann Arbor 48109, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Piccotti
authors.forename: K
authors.initials: K
authors.lastname: Li
authors.forename: S Y
authors.initials: SY
authors.lastname: Chan
authors.forename: J
authors.initials: J
authors.lastname: Ferrante
authors.forename: J
authors.initials: J
authors.lastname: Magram
authors.forename: E J
authors.initials: EJ
authors.lastname: Eichwald
authors.forename: D K
authors.initials: DK
authors.lastname: Bishop
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology; D016027:Heart Transplantation / Q000276:immunology; D007114:Immunization; D016130:Immunophenotyping; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D018664:Interleukin-12 / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D007519:Isoantigens / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008819:Mice, Nude; D018417:Th1 Cells / Q000276:immunology* / Q000378:metabolism; D018418:Th2 Cells / Q000378:metabolism
chemical_list: D016207:Cytokines; D007519:Isoantigens; D003208:Concanavalin A; D018664:Interleukin-12; D007371:Interferon-gamma