Smith M A, Naziruddin B, Poindexter N J, Haynes A E, Howard T, Mohanakumar T
Department of Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
Transplantation. 2000 Jan 15;69(1):157-62. doi: 10.1097/00007890-200001150-00026.
Significant levels of donor soluble human leukocyte antigen (HLA) class I (sHLA) are present in patients after transplants. We investigated the possibility that sHLA may inhibit cytolytic T lymphocyte (CTL) activity by inducing apoptosis of the CTL, thereby serving as a mechanism for specific tolerance.
sHLA-A2 and A3 were isolated from the sera of liver transplant recipients by affinity chromatography. T cell bulk lines directed against HLA-A2 and HLA-A3 were generated by stimulation with HLA-A2, A3+ peripheral blood leukocytes and B-lymphoblastoid cells. Induction of T cell apoptosis by sHLA was analyzed by adding sHLA to allospecific CTL 4 or for 24 hr before flow cytometric analysis of propidium iodide and fluorescein isothiocyanate-conjugated annexin V stained cells. T cell receptor (TCR) engagement by sHLA was demonstrated using a monoclonal antibody specific for the TCR.
sHLA-A3 inhibited CTL activity of a HLA-A3 T cell line by 53%, whereas sHLA-A2 had no effect. sHLA-A3 also increased T cell death by 77% over the control, whereas sHLA-A2 had no significant effect. However, sHLA-A2 induced 21% apoptosis of an anti-HLA-A2 T cell line, whereas sHLA-A3 caused only 3% apoptosis. The antibody complexed form of sHLA was ineffective in the induction of apoptosis. Preincubation of the T cells with anti-T cell receptor monoclonal antibody protected the T cells from sHLA-induced apoptosis, indicating that sHLA-TCR engagement is necessary for this process to occur.
TCR-mediated apoptosis of alloreactive CTL may serve as a mechanism by which sHLA can modulate the immune response.
移植后患者体内存在高水平的供体可溶性人类白细胞抗原I类分子（sHLA）。我们研究了sHLA通过诱导细胞毒性T淋巴细胞（CTL）凋亡来抑制CTL活性的可能性，从而将其作为一种特异性耐受的机制。
通过亲和层析从肝移植受者血清中分离出sHLA-A2和A3。用HLA-A2、A3 +外周血白细胞和B淋巴母细胞刺激产生针对HLA-A2和HLA-A3的T细胞群体系。在对碘化丙啶和异硫氰酸荧光素偶联的膜联蛋白V染色细胞进行流式细胞术分析之前，将sHLA加入同种异体特异性CTL中4小时或24小时，分析sHLA对T细胞凋亡的诱导作用。使用针对T细胞受体（TCR）的单克隆抗体证明sHLA与TCR结合。
sHLA-A3抑制HLA-A3 T细胞系的CTL活性达53%，而sHLA-A2无作用。与对照组相比，sHLA-A3还使T细胞死亡增加了77%，而sHLA-A2无显著作用。然而，sHLA-A2诱导抗HLA-A2 T细胞系21%的凋亡，而sHLA-A3仅引起3%的凋亡。sHLA的抗体复合形式在诱导凋亡方面无效。用抗T细胞受体单克隆抗体预孵育T细胞可保护T细胞免受sHLA诱导的凋亡，表明sHLA-TCR结合是该过程发生所必需的。
TCR介导的同种反应性CTL凋亡可能是sHLA调节免疫反应的一种机制。
