Chronic lymphocytic leukemia (CLL) is characterized by the peripheral accumulation of neoplastic B cells and is frequently complicated by the systemic immunosuppression associated with an impairment in B and T lymphocyte activation. We hypothesized that the expression of immune checkpoint suppressors B and T lymphocyte attenuator (BTLA) and cytotoxic T lymphocyte antigen (CTLA-4) is disturbed in both lymphocyte subpopulations in CLL. The expression of CTLA-4 and BTLA mRNA was determined by real-time PCR, while CTLA-4 protein expression (surface or intracellular) was estimated in BTLA+ lymphocytes by flow cytometry. In CLL patients, we observed a higher gene transcript level of BTLA and CTLA-4 than in healthy individuals in both freshly isolated and PMA stimulated B and T cells. Remarkably, lower amounts of both inhibitory proteins were found in peripheral blood (PB) CLL B cells, whereas normal BTLA and elevated CTLA-4 were found in T cells. Consistently, there was a prevalence of CTLA-4+ cells within circulating BTLA+ T cells cells of patients confronting PB healthy cells. After in vitro stimulation, the only change found in CLL patients was a decrease in BTLA expression in B and T lymphocytes. In contrast, healthy lymphocytes responded more vigorously as regards the BTLA and CTLA expression with substantially higher frequency of CD69+ cells under the stimulating condition compared to corresponding cells from the CLL group. Our results indicate that CLL development is associated with the affected expression of BTLA and CTLA-4 checkpoint receptors in PB and its impaired expression might be associated with lowering of the threshold for B cell activation and proliferation, while upregulated CTLA-4 expression in CLL peripheral BTLA+ T cells may contribute to suppressed T cell effector functions. This hypothesis needs to be validated in future studies, which would allow us to explain how the increased or decreased expression of these molecules affects the cell function.

中文翻译：

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慢性淋巴细胞白血病患者中BTLA和CTLA-4免疫检查点分子的异常表达。

慢性淋巴细胞性白血病（CLL）的特征是肿瘤性B细胞在周围积累，并经常因与B和T淋巴细胞活化受损相关的全身性免疫抑制而复杂化。我们假设在CLL的两个淋巴细胞亚群中，免疫检查点抑制剂B和T淋巴细胞减毒剂（BTLA）和细胞毒性T淋巴细胞抗原（CTLA-4）的表达均受到干扰。通过实时PCR确定CTLA-4和BTLA mRNA的表达，而通过流式细胞术估计BTLA +淋巴细胞中CTLA-4蛋白的表达（表面或细胞内）。在CLL患者中，我们观察到新鲜分离的和PMA刺激的B和T细胞中BTLA和CTLA-4的基因转录水平均高于健康个体。值得注意的是 在外周血（PB）CLL B细胞中发现两种抑制蛋白的含量较低，而在T细胞中发现正常的BTLA和升高的CTLA-4。一直以来，面对PB健康细胞的患者的循环BTLA + T细胞细胞中普遍存在CTLA-4 +细胞。后体外刺激，CLL患者唯一发现的改变是B和T淋巴细胞中BTLA表达的降低。相反，与来自CLL组的相应细胞相比，在刺激条件下，健康的淋巴细胞对BTLA和CTLA的表达反应更为强烈，其中CD69 +细胞在刺激条件下的频率要高得多。我们的结果表明，CLL的发展与PBLA中BTLA和CTLA-4检查点受体表达的受影响有关，其表达受损可能与降低B细胞活化和增殖的阈值有关，而CLL周围组织中CTLA-4表达上调BTLA + T细胞可能有助于抑制T细胞效应子的功能。这个假设需要在未来的研究中得到验证，