Cho S W, Kilmon M A, Studer E J, van der Putten H, Conrad D H
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298, USA.
Cell Immunol. 1997 Aug 25;180(1):36-46. doi: 10.1006/cimm.1997.1174.
The capacity of CD23 to regulate IgE production was evaluated in both an in vitro and an in vivo system. The decreased IgE response seen in CD23 transgenic mice was confirmed and observed to occur at all antigen doses used. In addition, purified B cells from the Tg animals in general exhibited lower IgE production when stimulated with CD40L and IL-4. To examine this down-regulating activity of CD23 an in vitro model system was developed. CHO cells were transfected with CD23, ICAM-1, or both CD23 and ICAM-1. ICAM-1 was chosen to enhance B cell-B cell interaction. Purified resting B cells were placed into culture with the mitomycin C-treated transfected or control CHO cells and activated with IL-4, IL-5, and CD40L-CHO. A dose-dependent decrease in IgE production was observed with increasing cell numbers of the CHO transfectants that expressed CD23. The effect lasted up to Day 3 of culture. B cell proliferation was also inhibited in a dose-dependent fashion by increasing numbers of CD23-expressing cells suggesting a potential effect of CD23 on B cell apoptosis. In contrast, ICAM-1-transfected or CHO control cells had minimal effects on either Ig production or B cell proliferation. While IgE production was inhibited up to 95% by high numbers of CD23-transfected CHO cells, some inhibition of IgG and IgM production was also seen. Finally, the mechanism of CD23-mediated inhibition of IgE production was compared with the inhibition in IgE production seen when B cell were coactivated with multivalent anti-IgD in conjunction with CD40L plus optimal IL-4. To this end we used RT-PCR to compare the relative levels of epsilon-germline transcripts in control cultures and cultures coactivated by anti-IgD, CD40L, and IL-5 or activated in the presence of high levels of CD23-expressing cells. CD22 was used as an internal standard since levels change little with B cell activation. Coactivation strongly inhibited epsilon-germline transcript levels but the presence of CD23-expressing cells did not. Thus, coactivation potentially operates prior to isotype switching, while high CD23 coculture blocks either recombination or more likely B cell differentiation to high Ig producers stage. Our data support the hypothesis that IL-4 induces both IgE and a controlling agent for IgE, namely, CD23.
在体外和体内系统中评估了CD23调节IgE产生的能力。在CD23转基因小鼠中观察到的IgE反应降低得到了证实，并且在所有使用的抗原剂量下均出现这种情况。此外，一般来说，来自转基因动物的纯化B细胞在用CD40L和IL-4刺激时表现出较低的IgE产生。为了研究CD23的这种下调活性，开发了一种体外模型系统。用CD23、ICAM-1或CD23和ICAM-1两者转染CHO细胞。选择ICAM-1来增强B细胞与B细胞的相互作用。将纯化的静息B细胞与经丝裂霉素C处理的转染或对照CHO细胞一起培养，并用IL-4、IL-5和CD40L-CHO激活。随着表达CD23的CHO转染细胞数量增加，观察到IgE产生呈剂量依赖性降低。这种作用持续到培养的第3天。表达CD23的细胞数量增加也以剂量依赖性方式抑制B细胞增殖，提示CD23对B细胞凋亡可能有影响。相比之下，转染ICAM-1的或CHO对照细胞对Ig产生或B细胞增殖的影响最小。虽然大量转染CD23的CHO细胞可将IgE产生抑制高达95%，但也观察到对IgG和IgM产生有一定抑制作用。最后，将CD23介导的IgE产生抑制机制与B细胞与多价抗IgD联合CD40L加最佳IL-4共激活时所见的IgE产生抑制进行了比较。为此，我们使用RT-PCR比较对照培养物以及由抗IgD、CD40L和IL-5共激活或在高水平表达CD23的细胞存在下激活的培养物中ε-种系转录本的相对水平。使用CD22作为内标，因为其水平随B细胞激活变化很小。共激活强烈抑制ε-种系转录本水平，但表达CD23的细胞的存在则不然。因此，共激活可能在同种型转换之前起作用，而高CD23共培养阻断重组或更可能阻断B细胞分化至高Ig产生细胞阶段。我们的数据支持IL-4诱导IgE和一种IgE控制因子即CD23的假说。
