| Summary: | 碩士 === 國立臺灣大學 === 免疫學研究所 === 91 === Inhibitory signals that govern the CD8+ T lymphocyte effector functions have been linked to the expression of natural killer cell receptors (NKRs) on effector CTLs. Abnormal up-regulation of inhibitory NKRs can potentially decrease the tumor-specific CTL activities by tumor-infiltrating lymphocytes (TILs). In order to evaluate the expression of inhibitory NKRs by TILs, we measured and compared the proportions of CD158a+, CD158b+, NKB1+, CD16/56+, CD161+, CD94+, and NKG2A+ fractions within gated T lymphocytes and their CD4/CD8+ subpopulations from PBMCs and TILs. Noted that when CD4+ T generally did not express any of the tested NKRs, CD3+CD8+ TILs from human cervical cancer (CC) expressed significantly higher CD94 and NKG2A and lower CD161 (NKR-P1A) than autologous counterparts from peripheral blood or normal cervixes. Comparisons on the expression of CD16/56, CD161, perforin, and granzyme B by gated T lymphocytes stressed the irrelevance of the CD56/CD161+, potentially cytotoxic NK-T and/or CD8+ CTL effector lineages to the tumor-specific immunity in CC milieu. The exploration of the co-expression of CD161 or CD56 and CD94/NKG2A further revealed that the majority of the induced NKG2A+CD8+ T lymphocytes, like the CC-infiltrating NKG2A+CD8+ T cells, were both CD56— and CD161—. Mixed autologous lymphocyte and tumor cell co-culture (MLTC) model demonstrated that up-regulated expression of CD94/NKG2A could be induced by certain CC tissue-derived mediators. From in vitro kinetic studies we further clarified that small amount of rIL-15 induced both high levels of CD94 and NKG2A up-regulation. Induced CD94 reached the highest level within 24 hours after rIL-15 treatment followed by the gradual up-regulation of NKG2A that initiated 1 -2 days behind and attained the comparative level at day 5. High dosages of rIL-12 (up to 30-100 ng/mL) or rIL-2 (up to 100-200 ng/mL) could also induce comparable levels of up-regulated CD94/NKG2A+ lymphocytes in vitro, but only carried different Th1/Tc1 cytokine-secreting and potential cytotoxicity abilities. IL-15-induced CD94/NKG2A up-regulation was mainly restricted to non-proliferating CD8bright T lymphocytes (compared with the up-regulation by CD8dim NK cells), which stressed the de novo nature of the expression. Like CC cells, rIL-15 could induce an almost uniformed NKG2A expression on CD3+CD94+NKG2A T cell fraction of PBMCs that was barely found in TILs. Immnohistochemical studies further showed the existence of IL-15 and TGF- within CC tissues, but not normal cervixes. Subsequently in ex vivo MLTC experiments we also found the possible dependence of endogenous IL-15, together with various amounts of endogenous IL-2, in CC tissue-induced CD94/NKG2A up-regulation. In conclusion, the up-regulation of inhibitory NKRs on CD8+ TILs revealed an as yet unidentified way modulated by cancer-derived mediators to impede the tumor-specific immune functions.
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