Adams P W, Lee H S, Waldman W J, Sedmak D D, Orosz C G
Department of Surgery, Ohio State University College of Medicine, Columbus 43210.
Transplantation. 1994 Aug 27;58(4):476-83.
We have investigated the contribution of monocytes (Mo) to the activation of purified human T cells by allogeneic human vascular endothelial cells (HUVEC). We have previously demonstrated that allogeneic HUVEC stimulate IL-2 production by CD8+ helper T lymphocytes (HTL), but not CD4+ HTL, in the absence of accessory Mo. We now show that addition of responder-autologous Mo to such cultures stimulates a high frequency of CD4+ HTL (1/6500), but no additional CD8+ HTL (1/35,000), as detected by limiting dilution analysis (LDA). The CD4+ HTL production of IL-2 increased with increasing numbers of Mo. Monoclonal antibodies to MHC class II interfered with HTL responses to allogeneic HUVEC in the presence, but not in the absence of autologous Mo. In contrast, IFN-gamma-treated HUVEC stimulated a high frequency of CD4+ HTL in the absence of autologous Mo. However, deletion experiments revealed that the population of HTL responsive to IFN-gamma-treated HUVEC is distinct from the population that responds to HUVEC in the presence of autologous Mo. These data suggest that Mo promote IL-2 production by presenting HUVEC-derived alloantigens via MHC class II molecules to CD4+ HTL, rather than by providing cytokines that promote more efficient IL-2 production by CD8+ HTL, or by inducing MHC class II expression on the HUVEC. In general, these data demonstrate that autologous Mo can play a significant role in the response of T cells to allogeneic HUVEC. Further, they demonstrate that the activation of human HTL by allogeneic HUVEC is complex, and can occur by at least three pathways: (1) direct stimulation of a small number of CD8+ HTL, but no CD4+ HTL, by quiescent HUVEC, (2) direct stimulation of a large number of CD4+ HTL by IFN-gamma-treated HUVEC, and (3) indirect stimulation of a different subset of CD4+ HTL by HUVEC in the presence of autologous monocytes. These three pathways of alloactivation are not unique to allogeneic HUVEC, but this experimental system provides a convenient and relevant model with which each pathway can be easily and independently investigated.
我们研究了单核细胞（Mo）在同种异体人血管内皮细胞（HUVEC）激活纯化的人T细胞过程中的作用。我们之前已经证明，在没有辅助性Mo的情况下，同种异体HUVEC可刺激CD8 +辅助性T淋巴细胞（HTL）产生白细胞介素-2（IL-2），但不能刺激CD4 + HTL产生IL-2。我们现在发现，在这种培养物中加入应答者自身的Mo可刺激高频率的CD4 + HTL（1/6500）产生，但通过有限稀释分析（LDA）检测发现，不会额外刺激CD8 + HTL产生（1/35,000）。随着Mo数量的增加，CD4 + HTL产生的IL-2也增加。针对MHC II类分子的单克隆抗体在有自身Mo存在时会干扰HTL对同种异体HUVEC的反应，但在没有自身Mo时则不会。相反，经干扰素-γ（IFN-γ）处理的HUVEC在没有自身Mo的情况下可刺激高频率的CD4 + HTL产生。然而，缺失实验表明，对经IFN-γ处理的HUVEC有反应的HTL群体与在有自身Mo存在时对HUVEC有反应的群体不同。这些数据表明，Mo通过经由MHC II类分子将HUVEC衍生的同种异体抗原呈递给CD4 + HTL来促进IL-2的产生，而不是通过提供细胞因子来促进CD8 + HTL更有效地产生IL-2，也不是通过诱导HUVEC上的MHC II类分子表达。总体而言，这些数据表明自身Mo在T细胞对同种异体HUVEC的反应中可发挥重要作用。此外，它们表明同种异体HUVEC对人HTL的激活是复杂的，并且至少可通过三种途径发生：（1）静止的HUVEC直接刺激少量CD8 + HTL，但不刺激CD4 + HTL；（2）经IFN-γ处理的HUVEC直接刺激大量CD4 + HTL；（3）在有自身单核细胞存在时，HUVEC间接刺激不同的CD4 + HTL亚群。这三种同种异体激活途径并非同种异体HUVEC所特有，但该实验系统提供了一个方便且相关的模型，利用此模型可以轻松且独立地研究每种途径。
