Motyka B, Bhogal H S, Reynolds J D
Department of Medical Physiology, University of Calgary, Canada.
Eur J Immunol. 1995 Jul;25(7):1865-71. doi: 10.1002/eji.1830250711.
The ileal Peyer's patch (PP) in sheep plays a central role in the development and production of B cells. Associated with a tremendous amount of B cell proliferation in this site is the extensive diversification of the Ig repertoire by somatic hypermutation. Very few (< 5%) of the B cells produced in the ileal PP differentiate and emigrate; instead, the vast majority of these cells soon die, and we have previously shown that death is associated with apoptosis. When placed in culture, ileal PP B cells die rapidly by apoptosis, such that after 24 h, 60 +/- 1% of DNA is fragmented. Here, we show that the extent of this spontaneous B cell apoptosis in culture, as quantitated by DNA fragmentation, was significantly increased in a dose-dependent manner by the glucocorticoids hydrocortisone or dexamethasone. Furthermore, treatment of lambs with 2-2.5 mg/kg of dexamethasone resulted in a marked increase in the number of apoptotic cells in the ileal PP and an increase in ileal PP B cell DNA fragmentation to 20 +/- 6%, compared with 2.4 +/- 0.1% in untreated lambs. Anti-immunoglobulin (Ig) antibodies also increased the extent of DNA fragmentation in cultured ileal PP B cells. After 24 or 48 h of culture with anti-Ig (PIg47A), DNA fragmentation was 74 +/- 2% and 75 +/- 3%, respectively. Ileal PP B cells are rescued from apoptosis by agents that activate protein kinase C and increase cytosolic Ca2+, and here we show that this treatment also results in apoptotic rescue in the presence of dexamethasone or anti-Ig. We speculate that the apoptosis of ileal PP B cells in situ may be modulated by glucocorticoids and by the cross-linking of surface Ig. Apoptosis, induced by a signal through surface Ig, may be an important mechanism in the deletion of self-reactive B cells during the expansion of the Ig repertoire in the ileal PP.
绵羊回肠派尔集合淋巴结（PP）在B细胞的发育和产生过程中发挥着核心作用。与该部位大量B细胞增殖相关的是，通过体细胞超突变实现免疫球蛋白库的广泛多样化。在回肠PP中产生的B细胞只有极少数（<5%）分化并迁移；相反，这些细胞中的绝大多数很快死亡，我们之前已经表明这种死亡与细胞凋亡有关。当置于培养中时，回肠PP B细胞会迅速通过凋亡死亡，以至于在24小时后，60±1%的DNA发生片段化。在此，我们表明，通过DNA片段化定量，培养中这种自发B细胞凋亡的程度会因糖皮质激素氢化可的松或地塞米松而以剂量依赖的方式显著增加。此外，用2 - 2.5mg/kg地塞米松处理羔羊，导致回肠PP中凋亡细胞数量显著增加，回肠PP B细胞DNA片段化增加至20±6%，而未处理羔羊为2.4±0.1%。抗免疫球蛋白（Ig）抗体也增加了培养的回肠PP B细胞中DNA片段化的程度。在用抗Ig（PIg47A）培养24或48小时后，DNA片段化分别为74±2%和75±3%。激活蛋白激酶C并增加胞质Ca2+的试剂可使回肠PP B细胞免于凋亡，在此我们表明这种处理在存在地塞米松或抗Ig的情况下也能导致凋亡挽救。我们推测，回肠PP B细胞在原位的凋亡可能受糖皮质激素和表面Ig交联的调节。由通过表面Ig的信号诱导的凋亡可能是在回肠PP中免疫球蛋白库扩展期间清除自身反应性B细胞的重要机制。
