Toker Ori, Broides Arnon, Lev Atar, Simon Amos J, Megged Orli, Shamriz Oded, Tal Yuval, Somech Raz, Lee Yu Nee, Nahum Amit
Faculty of Medicine, The Allergy and Immunology Unit, Hebrew University of Jerusalem, Shaare Zedek Medical Center, 12 Bayit Street, 91031, Jerusalem, Israel.
Immunology Clinic, Soroka University Medical Center, Beer-Sheva, Israel.
Immunol Res. 2022 Apr;70(2):216-223. doi: 10.1007/s12026-022-09263-2. Epub 2022 Jan 10.
X-linked agammaglobulinemia (XLA) is caused by mutations in the Bruton tyrosine kinase) BTK) gene. Affected patients have severely reduced amounts of circulating B cells. Patients with atypical XLA may have residual circulating B cells, and there are few studies exploring these cells' repertoire. We aimed to study the B cell repertoire of a novel hypomorphic mutation in the BTK gene, using the next generation sequencing (NGS) technology. Clinical data was collected from our clinical records. Real-time PCR was used to determine KREC copies, and NGS was used to determine the immunoglobulin (Ig) heavy chain (IgH) repertoire diversity. Both patients had a relatively mild clinical and laboratory phenotype, residual BTK protein expression, and the same novel mutation in the BTK gene, c.1841 T > C, p. L614P. Signal-joint kappa-deleting recombination excision circles (sj-KREC) for both patients were completely absent reflecting lack of naïve B cells. The intron RSS-Kde coding joints (cj) were significantly reduced, reflecting residual replicating B cells. NGS displayed restricted IgH repertoire with highly uneven distribution of clones, especially for Pt2. We report a novel BTK mutation, c.1841 T > C (p. L614P) that is associated with a relatively mild phenotype. We conclude that the IgH repertoire in atypical XLA is restricted with highly uneven distribution of clones. This phenomenon may be explained by extremely reduced to non-existent levels of BTK in B cells. This report sheds further light on atypical cases of XLA.
X连锁无丙种球蛋白血症（XLA）由布鲁顿酪氨酸激酶（BTK）基因突变引起。患病患者循环B细胞数量严重减少。非典型XLA患者可能有残余循环B细胞，而探索这些细胞库的研究很少。我们旨在利用下一代测序（NGS）技术研究BTK基因一种新的低表达突变的B细胞库。从我们的临床记录中收集临床数据。采用实时聚合酶链反应（PCR）测定KREC拷贝数，并用NGS测定免疫球蛋白（Ig）重链（IgH）库多样性。两名患者均有相对较轻的临床和实验室表型、残余BTK蛋白表达，且BTK基因存在相同的新突变，即c.1841 T＞C，p.L614P。两名患者的信号连接κ缺失重组切除环（sj-KREC）均完全缺失，这反映出幼稚B细胞缺乏。内含子RSS-Kde编码接头（cj）显著减少，反映出残余的增殖B细胞。NGS显示IgH库受限，克隆分布高度不均，尤其是Pt2患者。我们报告了一种与相对较轻表型相关的新的BTK突变，即c.1841 T＞C（p.L614P）。我们得出结论，非典型XLA中的IgH库受限，克隆分布高度不均。这种现象可能是由于B细胞中BTK水平极低甚至不存在所致。本报告进一步阐明了XLA的非典型病例。
