Kasid A, Bell G I, Director E P
Surgery Branch, National Cancer Institute, Bethesda, MD 20892.
J Immunol. 1988 Jul 15;141(2):690-8.
With subpopulations of human lymphoid cells that were enriched for lymphokine-activated killer (LAK) cell precursors, studies were performed to examine the effects of transforming growth factor-beta (TGF-beta) on their IL-2-dependent growth and differentiation to killer cells. The majority of the LAK precursor cells appeared to reside in nonadherent, non-T, and non-B lymphocyte populations that expressed CD11 and CD16 Ag. These cells were induced to proliferate and become LAK cells by high concentrations of rIL-2 alone in the apparent absence of any prior activation with mitogen or Ag. The partially purified lymphocyte subpopulations generated varying but several-fold greater levels of LAK killing on a per cell basis than did unfractionated lymphocytes. The exogenous addition of TGF-beta to the LAK precursor cultures, markedly inhibited IL-2-stimulated growth as well as the development of LAK activity in a dose-dependent manner. The antimitotic effect of TGF-beta was reversible; inhibition of proliferation could be largely restored by increasing the concentration of IL-2 in culture. In contrast, TGF-beta inhibition of cytotoxicity was relatively independent of the concentration of IL-2. Further, LAK precursors constitutively expressed TGF-beta mRNA and high affinity receptor for TGF-beta. Activation of LAK precursors with IL-2 alone, resulted in a three- to fivefold up-regulation of intracellular TGF-beta mRNA and TGF-beta biologic activity secreted in the culture media. Furthermore, Northern blotting revealed that the resting LAK precursors did not express the Tac-mRNA. Receptor binding studies with 125I-IL-2 suggested the presence of a single class of IL-2R with an apparent Kd of intermediate range (beta-chain of IL-2R) on the unstimulated cells. Stimulation with high concentrations of Il-2 induced Tac-mRNA (both the 3.5- and 1.5-kb transcripts) and resulted in the expression of high affinity IL-2R (Kd approximately 10(-11) M) on these cells. Suppression of IL-2-dependent responses by TGF-beta was accompanied by a selective down-regulation of the 1.5-kb Tac-mRNA as well as by reduction in high affinity IL-2R. The results suggest a negative autocrine control of TGF-beta on IL-2-dependent growth and differentiation of human LAK cells, possibly related to regulate the killer activation function.
利用富含淋巴因子激活的杀伤（LAK）细胞前体的人淋巴细胞亚群，开展了研究以检测转化生长因子-β（TGF-β）对其依赖白细胞介素-2（IL-2）的生长以及向杀伤细胞分化的影响。大多数LAK前体细胞似乎存在于表达CD11和CD16抗原的非黏附、非T和非B淋巴细胞群体中。在明显没有任何丝裂原或抗原预先激活的情况下，仅高浓度的重组人IL-2就能诱导这些细胞增殖并成为LAK细胞。与未分级的淋巴细胞相比，部分纯化的淋巴细胞亚群在每个细胞基础上产生的LAK杀伤水平有所不同，但高出数倍。向LAK前体培养物中外源添加TGF-β，以剂量依赖的方式显著抑制了IL-2刺激的生长以及LAK活性的发展。TGF-β的抗有丝分裂作用是可逆的；通过增加培养物中IL-2的浓度，增殖抑制作用可在很大程度上得到恢复。相比之下，TGF-β对细胞毒性的抑制相对独立于IL-2的浓度。此外，LAK前体组成性表达TGF-β mRNA和TGF-β的高亲和力受体。仅用IL-2激活LAK前体，导致细胞内TGF-β mRNA和培养基中分泌的TGF-β生物学活性上调三至五倍。此外，Northern印迹显示静息的LAK前体不表达Tac-mRNA。用125I-IL-2进行的受体结合研究表明，未刺激的细胞上存在一类表观解离常数处于中等范围的单一IL-2受体（IL-2R的β链）。用高浓度IL-2刺激可诱导Tac-mRNA（3.5 kb和1.5 kb转录本）表达，并导致这些细胞上高亲和力IL-2R（解离常数约为10^(-11) M）的表达。TGF-β对IL-2依赖反应的抑制伴随着1.5 kb Tac-mRNA的选择性下调以及高亲和力IL-2R的减少。结果表明TGF-β对人LAK细胞依赖IL-2的生长和分化存在负自分泌控制，这可能与调节杀伤激活功能有关。
