title: Role of endogenously produced interleukin-6 as a second signal in murine thymocyte proliferation induced by multiple cytokines: regulatory effects of transforming growth factor-beta.
abstract: Previous studies have demonstrated that murine thymocytes proliferate in the presence of submitogenic concentrations of phytohemagglutinin-P (PHA-P) and various cytokines such as interleukin-1 (IL-1), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6). We report that C3H/HeJ thymocytes stimulated with PHA-P and IL-1, IL-4, or TNF-alpha secrete significant levels of IL-6 as determined on B9 hybridoma cells. The possibility that thymocyte proliferation induced by these cytokines was mediated through IL-6 was investigated utilizing a neutralizing monoclonal antibody against murine IL-6, MP5 20F3.1. The results demonstrate that MP5 20F3.1 inhibited the proliferative response of thymocytes and B9 hybridoma cells to recombinant MuIL-6 (but not HuIL-6) and neutralized the endogenous IL-6 produced in the thymocyte cultures, but did not have any measurable effects on the proliferative responses induced by IL-1, IL-4, or TNF-alpha. Although the level of endogeneously produced IL-6 did not play a measurable role in the proliferative response induced by TNF-alpha, the addition of higher concentrations of IL-6 augmented the proliferation of murine thymocytes induced by rMu TNF-alpha. In addition, recombinant human transforming growth factor-beta 1 (rHu TGF-beta 1) significantly inhibited thymocyte proliferation induced by HuIL-1, rMuIL-4, rMuIL-6, and rMuTNF-alpha. The studies suggest that IL-1, IL-4, or TNF-alpha mediate a proliferative signal on murine thymocytes independent of IL-6 and that the proliferative signals provided by these cytokines as well as IL-6 are inhibitable by rHu TGF-beta 1.
authors.affiliation: Department of Immunology Research and Assay Technologies, Genentech, Inc., South San Francisco, California 94080.
authors.forename: K J
authors.initials: KJ
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Abrams
authors.forename: M
authors.initials: M
authors.lastname: Alphonso
authors.forename: M
authors.initials: M
authors.lastname: Pearce
authors.forename: G J
authors.initials: GJ
authors.lastname: Thorbecke
authors.forename: M A
authors.initials: MA
authors.lastname: Palladino
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D016207:Cytokines / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D011994:Recombinant Proteins / Q000494:pharmacology; D013950:Thymus Gland / Q000166:cytology* / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D015847:Interleukin-4