SIGNAL TRANSDUCTION THROUGH CYTOKINES AND THEIR RECEPTOR FOR B CELL GROWTH AND DIFFERENTIATION

(1) IL-5，以前称为n细胞替代因子（TRF）或B细胞生长因子II，诱导活化的B细胞产生Ig-。在非洲爪蟾卵母细胞中翻译的活性形式的IL-5的Mr为45 - 50 Kd，在还原条件下迁移到25 - 30 Kd，表明成熟的IL-5由同型二聚体组成。二聚体的形成是IL-5活性表达的必要条件。在2-ME存在的情况下，用n -聚糖酶处理IL-5使单体IL-5的Mr从25 - 30kd降低到12 - 14kd，表明IL-5是一个高度n -糖基化的蛋白。将tunicamycin和IL-5 MRNA共同注射到卵母细胞中，诱导产生27 Kd二聚体分子，发挥TRF和BCGF II的活性，这表明n -连接的碳水化合物部分在IL-5的生物活性中并不起重要作用。(2) IL-5诱导IgA的产生：ppd刺激的tbc型T细胞上清液可以提高dnp - ova刺激的dnp型B细胞中dnp特异性IgA的产生。纯化的rIL-5也能以剂量依赖性的方式增强抗dnp IgA的产生。这种增强作用不能被IL-1、IL-2、IL-3或IL-4所取代。lps刺激的B细胞多克隆IgA分泌优先被IL-5增强。表面iga阳性（sIgA^+） B细胞对IL-5有反应，而sIgA^- B细胞对IL-5无反应。这些结果表明，IL-5在抗原特异性和多克隆iga的形成中起重要作用。我们还研究了转化生长因子- β (tgf - β)对LPS刺激的B细胞产生IgA的影响。tgf - β本身可以选择性地增加多克隆IgA的产生。tgf - β)和IL-5协同增强了IgA的产生。IgA产生的动力学分析表明，tgf - β在培养早期发挥活性，而IL-5在培养后期才需要。sIgA^- B细胞对tgf - β有反应，从而产生分泌iga的细胞。综合所有结果，tgf - β在诱导IL-5产生IgA-方面具有不同的作用，并可能诱导IgA特异性的类别转换和sIgA^-细胞的成熟。(3) IL-5受体及功能：IL-5通过特定受体作用于靶细胞，IL-5有高亲和力和低亲和力两类。放射性标记IL-5的交联研究得到了两个92.5和160 Kd的交联复合物。用富集的T88-M细胞膜免疫大鼠获得了两种针对IL-5应答的T88-M细胞的单抗（H7和T21）。选择单克隆抗体竞争性抑制^<35> s标记IL-5的受体结合和IL-5的生物活性。来自腹膜的sIgM^< b> B细胞中90%以上为h7阳性，67%为Ly-l^+，并对IL-5有高频率的多克隆IgM产生反应。最后，H7和T21抗体特异性地从^<125> i标记的il - 5r阳性细胞裂解液中析出60 Kd蛋白。少

(1) IL-5, formerly called n-cell-replacing factor (TRF) or B-cell growth factor II, induces Ig- production of activated B cells. Active forms of IL-5 translated in Xenopus oocytes has Mr of 45 to 50 Kd, and migrate to a Mr of 25 to 30 Kd under reducing condition, indicating that mature IL-5 consists of homodimers. Dimer formation is obligatory for the expression of IL-5 activity. Treatment of the IL-5 with N-glycanase in the presence of 2-ME decreased Mr of monomer IL-5 from 25 to 30 Kd to 12 to 14 Kd, indicating that IL-5 is a heavily N-glycosylated protein. Co-injection of tunicamycin and IL-5 MRNA into oocytes induced the production of 27 Kd dimer molecules which exert TRF and BCGF II activity, suggesting that the N-linked carbohydrate moiety does not play an essential role in the biological activity of IL-5.(2) Induction of IgA production by IL-5: Supernatants from PPD-stimulated Tbc-primed T cells can enhance DNP-specific IgA production in cultures of DNP-OVA-stimulated DNP-primed … More B cells.Purified rIL-5 could also enhance anti-DNP IgA production in a dose dependent manner. This enhancing effect was not substituted by IL-1, IL-2, IL-3, or IL-4. Polyclonal IgA secretion of LPS-stimulated B cells was preferentially augmented by IL-5. Surface IgA-positive (sIgA^+) B cells, but not sIgA^- B cells responded to IL-5 for the development of IgA-secreting cells.These results indicate that IL-5 plays an essential role in the antigen-specific and polyclonal IgA-formation. Effects of transforming growth factor-beta (TGF-beta) on IgA production by LPS- stimulated B cells was also studied. TGF-beta itself could selectively augment polyclonal IgA production. TGF-beta) and IL-5 synergistically augmented IgA production. Kinetic analysis for IgA production revealed that TGF-beta exerted its activity early in the culture and IL-5 was required for late in the culture. sIgA^- B cells responded to TGF-beta for the development of IgA-secreting cells. Taking all results together, TGF-beta has differential role in the induction of IgA- production from IL-5 and may induce IgA-specific class-switching and maturation of sIgA^- cells.(3) IL-5 receptor and function: IL-5 acts on target cells via a specific receptor and there are two classes (high- and low-affinity) of IL-5. Cross-linking studies of radiolabeled IL-5 yielded two cross-linked complexes with 92.5 and 160 Kd. Two mabs (H7 and T21) to IL-5 responsive T88-M cells were obtained by immunizing a rat with enriched T88-M cell membranes. MAbs were selected for competitive inhibition of receptor binding of ^<35>S-labeled IL-5 and of IL-5 biological activities. More than 90% of sIgM^<> B cells from peritoneum are H7-positive and 67% of them are also Ly-l^+, and respond to IL-5 for polyclonal IgM production in a high frequency. Finally, both H7 and T21 antibodies specifically precipitate from ^<125>I-labeled IL-5R-positive cell lysates the 60 Kd protein. Less