title: Tumor growth alters T cell and macrophage production of and responsiveness to granulocyte-macrophage colony-stimulating factor: partial dysregulation through interleukin-10.
abstract: Tumor growth induces phenotypic and functional changes among splenic T cells and macrophages (M phi) that contribute to the immunosuppression observed in tumor-bearing hosts (TBH). These changes partly arise through alterations in immune cell production of and responsiveness to cytokines. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important T cell- and M phi-derived cytokine that is produced during normal host immunogenic challenge, but it's involvement during cancer is poorly defined. In contrast, interleukin-10 (IL-10) is an inhibitory cytokine that is produced by immune cells as a deactivation factor. IL-10 can disrupt GM-CSF synthesis and may be associated with tumor-induced changes in cytokine synthesis. We determined if tumor growth alters T-cell and M phi synthesis of and responsiveness to GM-CSF, and if these alterations occur because tumor growth heightens immune cell sensitivity to IL-10. Tumor growth significantly decreased T-cell synthesis of GM-CSF during activation by concanavalin A, and TBH T cells were more susceptible to GM-CSF synthesis inhibition by IL-10 than their normal host (NH) counterparts. This suppression was observed using both unseparated splenic lymphocyte preparations and purified CD4+ and CD8+ T cells. Similarly, TBH M phi (both splenic and peritoneal) produced less GM-CSF than NH M phi during activation by lipopolysaccharide. Tumor growth also altered major histocompatibility complex (MHC) class II- M phi GM-CSF synthesis. TBH M phi were more susceptible to GM-CSF synthesis inhibition by IL-10 than their NH counterparts. Although TBH T cells demonstrate less proliferation than NH T cells during activation, tumor growth did not compromise T-cell responsiveness to GM-CSF. However, tumor growth did increase TBH T-cell susceptibility to inhibition of proliferation by IL-10. Tumor growth suppressed M phi responsiveness to GM-CSF, and IL-10 further decreased M phi responsiveness to GM-CSF. Collectively, these results suggest that T cell and M phi production of and responsiveness to GM-CSF is disrupted during tumor growth, and that TBH T cells and M phi are more susceptible to the suppressor activity of IL-10 than their NH counterparts.
authors.affiliation: Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061-0406.
authors.forename: T M
authors.initials: TM
authors.lastname: Walker
authors.forename: C J
authors.initials: CJ
authors.lastname: Burger
authors.forename: K D
authors.initials: KD
authors.lastname: Elgert
mesh_terms: D000818:Animals; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis* / Q000494:pharmacology; D016753:Interleukin-10 / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D012513:Sarcoma, Experimental / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D016753:Interleukin-10; D016178:Granulocyte-Macrophage Colony-Stimulating Factor