Clinical Immunology Department, La Paz University Hospital, Lymphocyte Pathophysiology in Immunodeficiencies Group La Paz Institute for Health Research (IdiPAZ) and Center for Biomedical Network Research on Rare Diseases (CIBERER U767), Madrid, Spain.
Cancer Epigenetics Laboratory, INGEMM, Biomarkers and Experimental Therapeutics in Cancer Group, La Paz Institute for Health Research (IdiPAZ), Madrid, Spain.
Clin Exp Immunol. 2021 Mar;203(3):341-350. doi: 10.1111/cei.13522. Epub 2020 Oct 8.
Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by hypogammaglobulinemia and different degrees of B cell compartment alteration. Memory B cell differentiation requires the orchestrated activation of several intracellular signaling pathways that lead to the activation of a number of factors, such as nuclear factor kappa B (NF-κB) which, in turn, promote transcriptional programs required for long-term survival. The aim of this study was to determine if disrupted B cell differentiation, survival and activation in B cells in CVID patients could be related to defects in intracellular signaling pathways. For this purpose, we selected intracellular readouts that reflected the strength of homeostatic signaling pathways in resting cells, as the protein expression levels of the Bcl-2 family which transcription is promoted by NF-κB. We found reduced Bcl-2 protein levels in memory B cells from CVID patients. We further explored the possible alteration of this crucial prosurvival signaling pathway in CVID patients by analysing the expression levels of mRNAs from anti-apoptotic proteins in naive B cells, mimicking T cell-dependent activation in vitro with CD40L and interleukin (IL)-21. BCL-XL mRNA levels were decreased, together with reduced levels of AICDA, after naive B-cell activation in CVID patients. The data suggested a molecular mechanism for this tendency towards apoptosis in B cells from CVID patients. Lower Bcl-2 protein levels in memory B cells could compromise their long-term survival, and a possible less activity of NF-κB in naive B cells, may condition an inabilityto increase BCL-XL mRNA levels, thus not promoting survival in the germinal centers.
普通变异性免疫缺陷（CVID）是一种以低丙种球蛋白血症和不同程度 B 细胞区室改变为特征的原发性免疫缺陷。记忆 B 细胞分化需要几个细胞内信号通路的协调激活，这些信号通路导致许多因子的激活，如核因子 kappa B（NF-κB），其反过来促进长期存活所需的转录程序。本研究旨在确定 CVID 患者 B 细胞分化、存活和激活的缺陷是否与细胞内信号通路的缺陷有关。为此，我们选择了反映静止细胞中稳态信号通路强度的细胞内读数，如转录受 NF-κB 促进的 Bcl-2 家族的蛋白表达水平。我们发现 CVID 患者记忆 B 细胞中的 Bcl-2 蛋白水平降低。我们通过分析体外 CD40L 和白细胞介素（IL）-21 模拟 T 细胞依赖性激活时幼稚 B 细胞中抗凋亡蛋白的 mRNA 表达水平，进一步探讨了 CVID 患者这一关键存活信号通路可能发生的改变。在 CVID 患者中，幼稚 B 细胞激活后 BCL-XL mRNA 水平降低，同时 AICDA 水平降低。这些数据表明了 CVID 患者 B 细胞凋亡倾向的分子机制。记忆 B 细胞中 Bcl-2 蛋白水平降低可能会影响其长期存活，而幼稚 B 细胞中 NF-κB 活性降低可能会导致其无法增加 BCL-XL mRNA 水平，从而无法在生发中心促进存活。
