title: IL-6 enhances the cytotoxic activity of thymocyte-derived CD56+ cells.
abstract: Thymocyte-derived lymphokine-activated killer (LAK) cells were used as a model for the study of the cytokine driven development of cytotoxicity. These cells are devoid of initial cytotoxic activity but upon culture in IL-2 they develop into cytotoxic effectors. The parameters of the response of thymocytes to IL-6 are similar to that of PBL in that IL-6, at concentrations as low as 1 mu/ml, increases cytotoxicity of thymocyte-LAK cells when generated in low doses (25-50 mu/ml) of IL-2. IL-6-enhanced thymocyte-LAK cytotoxicity is observed when tested against both NK-resistant and NK-sensitive tumor cell lines. IL-6 alone does not induce any cytotoxicity from thymocytes nor does IL-6 change the time course of thymocyte-LAK cell generation in IL-2 culture. IL-6 does not affect DNA synthesis, total cell number, proportion of CD56+ cells, or the expression of IL-2R (both P55 and P75 glycoproteins) in IL-2-cultured thymocytes. Instead, IL-6 used to treat mature thymocyte-LAK effector cells for as little as 1 hr prior to 51Cr-release assay increases LAK cytotoxicity. This enhancement is abrogated by pretreatment of effector cells with cycloheximide, suggesting that protein synthesis is required for IL-6 to enhance LAK cell activity. The precursor phenotypes of IL-6-responsive thymocyte-LAK cells are CD3-/CD5-. The effector phenotypes of IL-6-enhanced thymocyte-LAK cells are CD5-/CD56+. Thus, IL-6 depends on synthesis of rapid-turnover proteins to act on mature CD56+/CD5- LAK cells to increase their cytotoxic function.
authors.affiliation: Department of Surgery, UCLA School of Medicine 90024.
authors.forename: S
authors.initials: S
authors.lastname: Iho
authors.forename: H
authors.initials: H
authors.lastname: Shau
authors.forename: S H
authors.initials: SH
authors.lastname: Golub
mesh_terms: D015703:Antigens, CD / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D019002:CD56 Antigen; D002454:Cell Differentiation; D002478:Cells, Cultured; D002648:Child; D003513:Cycloheximide / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D005786:Gene Expression Regulation; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology*; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects* / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology; D000093242:Interleukin-6 Inhibitors
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D019002:CD56 Antigen; D003513:Cycloheximide; D007376:Interleukin-2; D015850:Interleukin-6; D000093242:Interleukin-6 Inhibitors