Purkerson J M, Isakson P C
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville.
Eur J Immunol. 1991 Mar;21(3):707-14. doi: 10.1002/eji.1830210325.
Anti-immunoglobulin (Ig)-activated B lymphoblasts, prepared by culturing high-density B cells with anti-Ig-Sepharose for 48 h, can be induced to secrete IgM and IgG1 by a mixture of T cell-derived lymphokines containing interleukin (IL) 4. In this study we have examined the conditions required for lymphokine-mediated induction of IgG1 secretion and membrane (m)IgG1 expression in B lymphoblasts. Resting B cells exposed to IL 4 (10-100 U/ml) during anti-Ig-mediated blast transformation did not secrete IgG1 upon subsequent culture with lipopolysaccharide (LPS) regardless of whether IL 4 was present or absent during the secondary culture. In contrast, B lymphoblasts previously exposed to IL 4 did secrete IgG1 in response to T cell-derived lymphokines [EL 4 supernatant depleted of IL 4; (D)EL 4 SN]. However, optimal IgG1 secretion was obtained when B lymphoblasts were simultaneously exposed to IL 4 and other lymphokines. Pre-exposure to (D)EL 4 SN, which contains IL 5 and IL 2, failed to prepare anti-Ig blasts to secrete IgG1 in response to LPS and IL 4. Inhibition of IL 5 and IL 2 activity in EL 4 SN suppressed IL 4-mediated IgG1 secretion. Together, these data indicate that B lymphoblasts require IL 5 and IL 2 in addition to IL 4 to secrete IgG1, and that the IL 4 signal(s) must precede or accompany those provided by the other lymphokines. As a measure of the fraction of cells capable of switching to IgG1, we assessed expression of mIgG1 on B lymphoblasts by fluorescence flow cytometry. B lymphoblasts cultured for 3 days with (D)EL 4 SN and IL 4 (10-100 U/ml) were 8% to 20% mIgG1+; in the absence of IL 4 blasts did not express detectable mIgG1. Although anti-Ig blasts treated with LPS and IL 4 did not secrete appreciable IgG1, a substantial fraction of B lymphoblasts (4% - 19%) cultured with LPS and IL 4, but not LPS alone, expressed mIgG1. These results suggest that LPS and IL 4 are sufficient to commit B lymphoblasts to mIgG1 expression, but that additional signals provided by T cell-derived lymphokines are required to elicit IgG1 secretion.
通过将高密度B细胞与抗免疫球蛋白（Ig）-琼脂糖凝胶培养48小时制备的抗Ig激活的B淋巴母细胞，可被含有白细胞介素（IL）4的T细胞衍生淋巴因子混合物诱导分泌IgM和IgG1。在本研究中，我们检测了淋巴因子介导的B淋巴母细胞分泌IgG1及表达膜（m）IgG1所需的条件。在抗Ig介导的母细胞转化过程中暴露于IL 4（10 - 100 U/ml）的静息B细胞，在随后用脂多糖（LPS）培养时，无论二次培养过程中是否存在IL 4，均不分泌IgG1。相反，先前暴露于IL 4的B淋巴母细胞确实会响应T细胞衍生的淋巴因子[去除IL 4的EL 4上清液；（D）EL 4 SN]而分泌IgG1。然而，当B淋巴母细胞同时暴露于IL 4和其他淋巴因子时，可获得最佳的IgG1分泌。预先暴露于含有IL 5和IL 2的（D）EL 4 SN，未能使抗Ig母细胞响应LPS和IL 4而分泌IgG1。抑制EL 4 SN中的IL 5和IL 2活性可抑制IL 4介导的IgG1分泌。总之，这些数据表明，B淋巴母细胞除了IL 4外还需要IL 5和IL 2来分泌IgG1，并且IL 4信号必须先于或伴随其他淋巴因子提供的信号。作为能够转换为IgG1的细胞比例的一种衡量方法，我们通过荧光流式细胞术评估了B淋巴母细胞上mIgG1的表达。用（D）EL 4 SN和IL 4（10 - 100 U/ml）培养3天的B淋巴母细胞中，8%至20%为mIgG1阳性；在没有IL 4的情况下，母细胞不表达可检测到的mIgG1。尽管用LPS和IL 4处理的抗Ig母细胞不分泌可观的IgG1，但用LPS和IL 4（而非单独的LPS）培养的相当一部分B淋巴母细胞（4% - 19%）表达mIgG1。这些结果表明，LPS和IL 4足以使B淋巴母细胞定向表达mIgG1，但需要T细胞衍生淋巴因子提供的额外信号来引发IgG1分泌。
