de Graav Gretchen N, Hesselink Dennis A, Dieterich Marjolein, Kraaijeveld Rens, Weimar Willem, Baan Carla C
Department of Internal Medicine, Section of Transplantation and Nephrology, Erasmus MC, University Medical Center, Rotterdam, the Netherlands.
PLoS One. 2016 Feb 26;11(2):e0148604. doi: 10.1371/journal.pone.0148604. eCollection 2016.
The co-stimulatory inhibitor of the CD28-CD80/86-pathway, belatacept, allows calcineurin-inhibitor-free immunosuppression in kidney transplantation. However, aggressive T-cell mediated allogeneic responses have been observed in belatacept-treated patients, which could be explained by effector-memory T-cells that lack membrane expression of CD28, i.e. CD28-negative (CD28NULL) T-cells. CD28-positive (CD28POS) T-cells that down regulate their surface CD28 after allogeneic stimulation could also pose a threat against the renal graft. The aim of this study was to investigate this potential escape mechanism for CD28POS T-cells under belatacept treatment.
MATERIALS & METHODS: PBMCs, isolated T-cell memory subsets and isolated CD28POS T-cells were obtained from end-stage renal disease (ESRD) patients and co-cultured with allo-antigen in the presence of belatacept to mimic allogeneic reactions in kidney-transplant patients under belatacept treatment. As a control, IgG was used in the absence of belatacept.
Despite high in vitro belatacept concentrations, a residual T-cell growth of ±30% was observed compared to the IgG control after allogeneic stimulation. Of the alloreactive T-cells, the majority expressed an effector-memory phenotype. This predominance for effector-memory T-cells within the proliferated cells was even larger when a higher dose of belatacept was added. Contrary to isolated naïve and central-memory T cells, isolated effector-memory T cells could not be inhibited by belatacept in differentiation or allogeneic IFNγ production. The proportion of CD28-positive T cells was lower within the proliferated T cell population, but was still substantial. A fair number of the isolated initially CD28POS T-cells differentiated into CD28NULL T-cells, which made them not targetable by belatacept. These induced CD28NULL T-cells were not anergic as they produced high amounts of IFNγ upon allogeneic stimulation. The majority of the proliferated isolated originally CD28POS T-cells, however, still expressed CD28 and also expressed IFNγ.
This study provides evidence that, apart from CD28NULL T-cells, also CD28POS, mostly effector-memory T-cells can mediate allogeneic responses despite belatacept treatment.
CD28 - CD80/86通路的共刺激抑制剂贝拉西普可使肾移植患者在无钙调神经磷酸酶抑制剂的情况下实现免疫抑制。然而，在接受贝拉西普治疗的患者中观察到了侵袭性T细胞介导的同种异体反应，这可能是由缺乏CD28膜表达的效应记忆T细胞（即CD28阴性（CD28NULL）T细胞）所导致的。同种异体刺激后下调其表面CD28的CD28阳性（CD28POS）T细胞也可能对肾移植构成威胁。本研究的目的是探讨在贝拉西普治疗下CD28POS T细胞的这种潜在逃逸机制。
从终末期肾病（ESRD）患者中获取外周血单个核细胞（PBMCs）、分离的T细胞记忆亚群和分离的CD28POS T细胞，并在贝拉西普存在的情况下与同种异体抗原共培养，以模拟接受贝拉西普治疗的肾移植患者的同种异体反应。作为对照，在无贝拉西普的情况下使用IgG。
尽管体外贝拉西普浓度较高，但同种异体刺激后与IgG对照相比，仍观察到约±30%的残余T细胞生长。在同种异体反应性T细胞中，大多数表现出效应记忆表型。当添加更高剂量的贝拉西普时，增殖细胞中效应记忆T细胞的这种优势更加明显。与分离的初始和中枢记忆T细胞不同，分离的效应记忆T细胞在分化或同种异体干扰素γ产生方面不能被贝拉西普抑制。增殖的T细胞群体中CD28阳性T细胞的比例较低，但仍然可观。相当数量的最初分离的CD28POS T细胞分化为CD28NULL T细胞，这使得它们不能被贝拉西普靶向。这些诱导产生的CD28NULL T细胞并非无反应性，因为它们在同种异体刺激后产生大量干扰素γ。然而，大多数增殖的最初分离的CD28POS T细胞仍表达CD28并产生干扰素γ。
本研究提供了证据，表明除了CD28NULL T细胞外，CD28POS（主要是效应记忆T细胞）在贝拉西普治疗下也可介导同种异体反应。
