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免疫抑制活性を持つ同系マウス肉腫特異的CD4⁺Ｔ細胞の性状：付体輝, 沈淵,　藤本重義（高知医大・免疫）

Characteristics of specific CD4⁺T cell clone for syngeneic murine sarcoma with immunosuppressive activity : Tihui FU, Yuan SHEN, Shigeyoshi FUJIMOTO (Dept. of Immunol., Kochi Med. Sch.)

Presence of CD4⁺ suppressor T cells in tumor bearing hosts was postulated by results that depletion of CD4⁺ T cells from tumor growing mice by i.v. injection of anti-CD4 mAb induced the tumor regression in mice. In this study, in order to characterize the CD4⁺ suppressor T cells and their suppression, a CD4⁺ T cell clone designated T595B1 capable of down-regulating in vitro CTL induction, was established from a syngeneic sarcoma S713a bearing A/J mouse spleen cells. T595B1 showed specific proliferative response to T cell depleted S713a bearing syngeneic accessory cells. It expressed CD3, TCR-β, CD4, CD25, CD45RB, LFA-1 and ICAM-1 molecules on its cell surface. From secreted cytokine analyses by ELISA and bioassay, IL-4, IL-6, and IL-10 but not TNF were detected in its culture supernatant after stimulation, thus indicating that T595B1 belonged to Th-2 type subset. T595B1 cells as well as their culture supernatant remarkably down-regulated in vitro CTL induction against S713a in a dose dependent manner. Furthermore, the suppressive activity was not neutralized by anti-IL-4 and/or anti-IL-10, anti-pan TGFβor anti-VEGF neutralizing Abs., suggesting that some novel cytokine(s) will be responsible for this suppression. Since CTL induction against S713a in immune spleen cells did not require the presence of CD4 T cells, this suppressive factor(s) may directly act on CD8 CTL population.