title: The role of IL-12 in maintaining resistance to Leishmania major.
abstract: IL-12p40 is required for the maintenance of resistance during Leishmania major infection. In this study, we addressed how IL-12 mediates this function. First, we demonstrated that both subunits of IL-12, p40 and p35, were required for continued resistance to L. major. Second, using IL-12, IL-4 doubly deficient mice, we investigated the possibility that IL-12 inhibits IL-4-induced outgrowth of Th2 cells that might compete with Th1 cells. We found that even in the absence of a Th2 response, IL-12 was still required to maintain resistance. Next, using adoptive transfer of Thy-1 disparate CD4(+) T cells from L. major-healed mice, we were able to show that the loss of a protective response in L. major-infected IL-12-deficient mice is linked with the loss of Th1 cells. In contrast, there was an equal recovery of CD4(+) Th1 cells from wild-type and IL-12-deficient mice when transferred into mice that were not challenged with L. major. The ability of Th1 cells to survive regardless of IL-12 levels in the absence of Ag stimulation was confirmed by adoptive transfer studies of CD4(+) Th1 cells from DO11.10 TCR transgenic mice. Taken together, these results indicate that, rather than modulating Th2 responses or optimizing IFN-gamma production, the critical role for IL-12 in maintaining cell-mediated immunity may be to prevent the loss of Th1 cells during a challenge infection.
authors.affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104. Department of Environmental Sciences, Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Audrey Y
authors.initials: AY
authors.lastname: Park
authors.forename: Brian
authors.initials: B
authors.lastname: Hondowicz
authors.forename: Manfred
authors.initials: M
authors.lastname: Kopf
authors.forename: Phillip
authors.initials: P
authors.lastname: Scott
mesh_terms: D000818:Animals; D005260:Female; D007111:Immunity, Cellular; D018664:Interleukin-12 / Q000502:physiology*; D053765:Interleukin-12 Subunit p35; D053762:Interleukin-12 Subunit p40; D018320:Leishmania major / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D021122:Protein Subunits; D018417:Th1 Cells / Q000502:physiology*; D018418:Th2 Cells / Q000502:physiology
chemical_list: D053765:Interleukin-12 Subunit p35; D053762:Interleukin-12 Subunit p40; D021122:Protein Subunits; D018664:Interleukin-12