ANALYSIS OF ISOTYPE AND IDIOTYPE EXPRESSION IN XID MICE

T非依赖性（TI）B细胞应答对于产生 针对细菌荚膜多糖（TI-2抗原）的抗体，和 因此在抗细菌免疫应答中起重要作用。 它有 有人提出这些反应是由免疫球蛋白（IG）介导的 通过多糖上的重复决定簇进行受体交联， 某些具有X染色体连锁遗传缺陷xid的小鼠品系， 不会产生这种抗体反应。 据报道，这些老鼠 缺失拟定需要的B细胞亚群，即LyB-5+细胞 用于TI B细胞应答。 某些免疫球蛋白同位素的血清水平 由T非依赖性B细胞应答产生的IgG 3和IgM， XID小鼠相对于其他遗传上相同的无缺陷小鼠。 相反，xid小鼠中伊加水平较高。 有人建议 Lyb-5细胞转换为并产生IgG 3的能力较低， 同种型 我们的数据表明，第三种同种型，IgG 2b，是超过- 在一些xid小鼠中表达。 我们还发现使用LPS培养 引导B细胞从xid转换为IgG 3和IgG 2 B的系统 小鼠在转换为IgG 3或产生IgG 3方面没有损伤， 他们是否有倾向于转换为IgG 2b。 因此， 低IgM和IgG 3是由xid B细胞缺乏反应引起的 细菌TI-2抗原的环境刺激。 我们 目前正在研究IgG 2b表达升高的基础， 和伊加。 以前曾报道，来自xid小鼠的B细胞 与正常B细胞在免疫球蛋白V区的使用上不同。 我们实验室 已经使用B细胞集落滤纸片杂交试验证明 尽管V区域使用在xid和xd之间平均相似， 正常小鼠，小鼠之间的差异在xid中是明显的，但在正常B中不是 细胞 我们目前正在研究这种情况的遗传基础 现象

T-independent (TI) B cell responses are critical for the production of antibodies to bacterial capsular polysaccharides (TI-2 antigens), and thus play an important role in anti-bacterial immune responses. It has been proposed that these responses are mediated by immunoglobulin (Ig) receptor cross-linking by repeating determinants on the polysaccharides, Certain strains of mice with an X chromosome linked genetic defect, xid, do not mount such antibody responses. These mice are reported to be missing a subset of B cells, the Lyb-5+ cells, proposed to be required for TI B cell responses. Serum levels of certain immunoglobulin isotopes produced by T independent B cell responses, IgG3 and IgM, are lower in xid mice relative to otherwise genetically identical non-defective mice. Conversely, IgA levels are higher in xid mice. It has been suggested that Lyb-5- cells are less able to switch to and produce the IgG3 isotype. Our data demonstrates that a third isotype, IgG2b, is over- expressed in some xid mice. We also have found using an LPS culture system that directs switching to IgG3 and IgG2b that B cells from xid mice do not have an impairment in switching to or production of IgG3, nor do they have a propensity to switch to IgG2b. Thus, it is more likely that the low IgM and IgG3 is caused by a lack of response of xid B cells to environmental stimulation by bacterial TI-2 antigens. We are currently investigating the basis for the elevated expression of IgG2b and IgA. It has been reported previously that B cells from xid mice differ from normal B cells in usage of immunoglobulin V regions. Our lab has demonstrated using a B cell colony filter disk hybridization assay that although V region usage is on the average similar between xid and normal mice, variation between mice is evident in xid but not normal B cells. We are currently investigating the genetic basis of this phenomenon.