Simon H U, Mills G B, Hashimoto S, Siminovitch K A
Department of Medicine, University of Toronto, Ontario, Canada.
J Clin Invest. 1992 Oct;90(4):1396-405. doi: 10.1172/JCI116006.
B lymphocytes from patients expressing the X chromosome-linked immune deficiency disorder, Wiskott-Aldrich syndrome (WAS), fail to produce antibodies in response to stimulation with polysaccharides and other type-2 T cell-independent antigens. To investigate whether this abnormality reflects a defect in the signal transduction cascade normally triggered by ligation of surface immunoglobulin (sIg) on B cells, we have examined early signaling events induced by anti-Ig antibody stimulation of EBV B lymphoblastoid cell lines from WAS patients and healthy controls. Despite the expression of comparable levels of sIg and sIgM on WAS and control EBV B cells, WAS cells failed to manifest the increased proliferation in response to anti-Ig treatment observed in the control cell lines. WAS and control EBV B cells also differed in the magnitude of the change in cytosolic free calcium ([Ca2+]i) induced by sIg ligation; WAS cells showed either markedly diminished or no changes in [Ca2+]i levels whereas control EBV B cells consistently showed increases in [Ca2+]i. Anti-Ig-induced changes in inositol phosphate release were also markedly reduced in WAS compared with control cells. As protein tyrosine phosphorylation is thought to represent a proximal event in the activation of B cells, inducing increases in [Ca2+]i by virtue of tyrosine phosphorylation of phospholipase C (PLC)-gamma, profiles of protein tyrosine phosphorylation and expression of tyrosine-phosphorylated PLC-gamma 1 were compared between WAS and normal EBV B cells before and after sIg cross-linking. These studies revealed that in addition to defective mobilization of Ca2+, the WAS cells manifested little or no increase in tyrosine phosphorylation of PLC-gamma 1 or other intracellular proteins after sIg ligation. Together these results indicate the association of WAS with a defect in the coupling of sIg to signal transduction pathways considered prerequisite for B cell activation, likely at the level of tyrosine phosphorylation. The abnormalities observed in these early transmembrane signaling events in WAS EBV B cells may play a role not only in the nonresponsiveness of WAS patient B cells to certain T independent antigens, but also in the genesis of some of the other cellular deficits exhibited by these patients.
患有X染色体连锁免疫缺陷疾病——威斯科特-奥尔德里奇综合征（WAS）的患者的B淋巴细胞，在受到多糖和其他2型非T细胞依赖性抗原刺激时无法产生抗体。为了研究这种异常是否反映了正常情况下由B细胞表面免疫球蛋白（sIg）连接引发的信号转导级联反应中的缺陷，我们检测了来自WAS患者和健康对照的EBV B淋巴母细胞系在抗Ig抗体刺激下诱导的早期信号事件。尽管WAS和对照EBV B细胞上sIg和sIgM的表达水平相当，但WAS细胞在抗Ig处理后未能表现出对照细胞系中观察到的增殖增加。WAS和对照EBV B细胞在sIg连接诱导的胞质游离钙（[Ca2+]i）变化幅度上也存在差异；WAS细胞的[Ca2+]i水平要么显著降低，要么没有变化，而对照EBV B细胞的[Ca2+]i水平持续升高。与对照细胞相比，WAS中抗Ig诱导的肌醇磷酸释放变化也明显减少。由于蛋白酪氨酸磷酸化被认为是B细胞激活的近端事件，通过磷脂酶C（PLC）-γ的酪氨酸磷酸化诱导[Ca2+]i增加，我们比较了WAS和正常EBV B细胞在sIg交联前后的蛋白酪氨酸磷酸化谱和酪氨酸磷酸化PLC-γ1的表达。这些研究表明，除了Ca2+动员缺陷外，WAS细胞在sIg连接后PLC-γ1或其他细胞内蛋白的酪氨酸磷酸化几乎没有增加或没有增加。这些结果共同表明，WAS与sIg与被认为是B细胞激活先决条件的信号转导途径的偶联缺陷有关，可能在酪氨酸磷酸化水平上。在WAS EBV B细胞中这些早期跨膜信号事件中观察到的异常，可能不仅在WAS患者B细胞对某些非T细胞依赖性抗原的无反应性中起作用，而且在这些患者表现出的一些其他细胞缺陷的发生中也起作用。
