Tromp Samantha A M, van Leeuwen Ester M M, Jansen Machiel H, Kwakernaak Arjan J, Bomers Marije K, Jonkers René E, van Spaendonk Resie M L, Kuijpers Taco W, de Bree Godelieve J
Department of Pediatric Immunology, Rheumatology and Infectious Diseases, Emma Children's Hospital & Center for Immunodeficiency and Immune dysregulation Amsterdam, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands; Department of Experimental Immunology, Center for Immunodeficiency and Immune Dysregulation Amsterdam, Amsterdam Institute for Immunology and Infectious Diseases, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
Department of Experimental Immunology, Center for Immunodeficiency and Immune Dysregulation Amsterdam, Amsterdam Institute for Immunology and Infectious Diseases, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands; Department of Laboratory Medicine, Laboratory Specialized Diagnostics and Research, Section Medical Immunology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
Clin Immunol. 2025 Jul 10;280:110565. doi: 10.1016/j.clim.2025.110565.
Genetic variants in Cytotoxic T-Lymphocyte-associated protein 4 (CTLA4) and LPS responsive beige-like anchor protein (LRBA), involved in the same biological pathways, are implicated as monogenic causes of Common Variable Immunodeficiency Disorder (CVID). The pitfall in the recognition of CVID possibly related to CTLA-4 haploinsufficiency or LRBA deficiency is a clinical picture that is very heterogeneous. In the present study, we illustrate this challenge by means of clinical and immunological analysis of five patients with novel genetic variants in CTLA4 and LRBA.
Whole-exome sequencing (WES) was performed to identify genetic variants in the currently known immune genes in patients. Extensive immunophenotyping, lymphocyte proliferation assays and expression of CTLA-4 and a panel of 17 co-stimulatory molecules, both in rest and upon activation, were performed to gain insight into the impact of the genetic variants on B and T cell phenotype and function.
A novel heterozygous variant in CTLA4 (c.457 + 5G > A) was identified in three members of a single family, all presenting with different clinical manifestations. In two additional patients, two genetic variants in LRBA (c.1771 T > C; c.2450-3C > A) were found, of which one is novel as well. The B cell phenotype was naïve with absence of non-switched and switched memory B cells in all patients except of the genetically affected elderly woman without any clinical manifestations. CD4 and CD8 T cell numbers and phenotype were normal. Differentiation of B cells into antibody secreting cells in vitro was reduced, especially in response to T cell-independent stimulation. The T cells showed impaired upregulation of CTLA-4 expression, which was most pronounced in CD4CD25FoxP3 regulatory T cells, which helped to biologically support the genetic diagnosis.
The described novel genetic variants in CTLA4 and LRBA show immunological impact and are therefore likely to underly an immune dysregulation syndrome with a highly variable clinical presentation. Apart from the immunophenotypic abnormal findings in activated T cells, the intrinsic B cell defect aids in the interpretation of novel genetic variants in these two genes in the context of a highly suspected clinical presentation.
细胞毒性T淋巴细胞相关蛋白4（CTLA4）和LPS反应性米色样锚定蛋白（LRBA）中的基因变异参与相同的生物学途径，被认为是常见可变免疫缺陷病（CVID）的单基因病因。识别可能与CTLA - 4单倍体不足或LRBA缺乏相关的CVID的陷阱在于其临床表现非常异质性。在本研究中，我们通过对5例CTLA4和LRBA基因新变异患者进行临床和免疫学分析来说明这一挑战。
对患者进行全外显子测序（WES）以鉴定目前已知免疫基因中的基因变异。进行广泛的免疫表型分析、淋巴细胞增殖试验以及CTLA - 4和一组17种共刺激分子在静息和激活状态下的表达分析，以深入了解基因变异对B细胞和T细胞表型及功能的影响。
在一个单一家族的三名成员中鉴定出CTLA4中的一种新的杂合变异（c.457 + 5G > A），他们均表现出不同的临床表现。在另外两名患者中，发现了LRBA中的两种基因变异（c.1771 T > C；c.2450 - 3C > A），其中一种也是新的。除了无任何临床表现的受基因影响的老年女性外，所有患者的B细胞表型均为幼稚型，缺乏未转换和转换记忆B细胞。CD4和CD8 T细胞数量及表型正常。体外B细胞分化为抗体分泌细胞的能力降低，尤其是对非T细胞依赖性刺激的反应。T细胞显示CTLA - 4表达上调受损，这在CD4CD25FoxP3调节性T细胞中最为明显，这有助于从生物学上支持基因诊断。
所描述的CTLA4和LRBA中的新基因变异显示出免疫学影响，因此可能是一种临床表现高度可变的免疫失调综合征的基础。除了激活的T细胞中免疫表型异常发现外，内在的B细胞缺陷有助于在高度怀疑的临床背景下解释这两个基因中的新基因变异。
