Nonoyama S, Tsukada S, Yamadori T, Miyawaki T, Jin Y Z, Watanabe C, Morio T, Yata J, Ochs H D
Department of Pediatrics, University of Washington, Seattle 98195, USA.
J Immunol. 1998 Oct 15;161(8):3925-9.
X-linked agammaglobulinemia (XLA) is a primary immunodeficiency disease caused by mutations of Bruton tyrosine kinase (Btk); Btk plays an essential role in the development of mature B cells. However, small numbers of B cells ("leaky B cells") are present in the peripheral blood of most XLA patients. In this study, we analyzed the function of these leaky B cells obtained from XLA patients. Enough numbers of B cells were available for analysis from five of nine XLA patients originally screened. Sequence analysis revealed missense mutations of Btk in four of the five XLA patients. No mutation was found in the coding region of Btk in one patient. Western blotting and/or flow cytometric analysis failed to detect Btk protein in all five patients. B cells isolated from peripheral blood of these XLA patients were CD5-, CD20+, CD19+, and CD21-. If stimulated with anti-CD40 and IL-4, XLA B cells proliferated normally and produced significant amounts of IgE. Anti-CD40 stimulation of XLA B cells resulted in normal expression of CD23. In addition, three of the five XLA patients studied were immunized with bacteriophage phiX174 and produced low but detectable levels of antiphage-specific Ab. Similarly, X-linked immunodeficiency mice, which carry a missense mutation in Btk, produced substantial amounts of antiphage Ab. These results indicate that CD40 signaling is intact in B cells lacking demonstrable Btk, and that leaky B cells in XLA patients can proliferate, undergo isotype switching, and differentiate into specific Ab-producing cells.
X连锁无丙种球蛋白血症（XLA）是一种由布鲁顿酪氨酸激酶（Btk）突变引起的原发性免疫缺陷病；Btk在成熟B细胞的发育中起关键作用。然而，大多数XLA患者外周血中存在少量B细胞（“渗漏B细胞”）。在本研究中，我们分析了从XLA患者获得的这些渗漏B细胞的功能。最初筛查的9例XLA患者中有5例可获得足够数量的B细胞用于分析。序列分析显示，5例XLA患者中有4例存在Btk错义突变。1例患者的Btk编码区未发现突变。在所有5例患者中，蛋白质印迹法和/或流式细胞术分析均未检测到Btk蛋白。从这些XLA患者外周血中分离的B细胞为CD5-、CD20+、CD19+和CD21-。用抗CD40和IL-4刺激后，XLA B细胞正常增殖并产生大量IgE。抗CD40刺激XLA B细胞导致CD23正常表达。此外，所研究的5例XLA患者中有3例用噬菌体phiX174免疫，产生了低水平但可检测到的抗噬菌体特异性抗体。同样，携带Btk错义突变的X连锁免疫缺陷小鼠产生了大量抗噬菌体抗体。这些结果表明，在缺乏可证实的Btk的B细胞中，CD40信号通路是完整的，并且XLA患者中的渗漏B细胞可以增殖、进行同种型转换并分化为产生特异性抗体的细胞。
