Lycke N, Strober W
Mucosal Immunity Section, National Institute of Allergy and Infectious Disease, Bethesda, MD 20892.
J Immunol. 1989 Jun 1;142(11):3781-7.
Cholera toxin (CT) is a powerful oral immunogen and adjuvant that elicits strong IgG and IgA antibody responses. In our study we investigated whether this property of CT was associated with an effect on B cell isotype differentiation. Initially, we determined the effect of CT on normal LPS-induced Peyer's patch B cells and found that whereas CT is strongly inhibitory of IgM production, it increases by approximately three-fold the number and frequency of IgG- and IgA-producing cells. Subsequently, using cell sorting technology, we demonstrated that CT acts on membrane (m)IgM+, mIgG/mIgA- B cells rather than mIgG/mIgA+ B cells. In addition, we showed that CT does not cause selective inhibition of mIgM, or enhancement of mIgG/mIgA B cell proliferation. In parallel studies we determined the effect of CT on the differentiation of a clonal B cell population, CH12.LX cells, i.e., a population comprised mainly of mIgM+ cells (98%) admixed with a small subpopulation of mIgA+ cells (2%). Here we found that CT (in the absence of LPS) causes a rapid decrease (24 h) in the intensity of mIgM expression as well as a marked increase in the size of the subpopulation expressing mIgA. In addition, we found that CT (in the presence of LPS), inhibits CH12.LX IgM production while increasing the absolute number and frequency of IgA-producing cells. In contrast, CT inhibits IgA production by CH12.LX.A2 cells, a subclone of CH12.LX cells that bears only IgA. Finally, we demonstrated that CT is equally inhibitory of the proliferation of CH12.LX cells and CH12.LX.A2 cells. Taken together, these effects of CT on normal B cells and a clonal B cell line indicate that CT induces substantial numbers of mIgM+ cells to undergo isotype differentiation into mIgG+ or mIgA+ B cells. In a final series of studies we showed that the effect of CT on isotype differentiation was mimicked by the B subunit of CT, i.e., the subunit that does not activate intracellular adenylate cyclase; thus the induction of isotype differentiation by CT is not mediated by a perturbation in cAMP level.
霍乱毒素（CT）是一种强大的口服免疫原和佐剂，可引发强烈的IgG和IgA抗体反应。在我们的研究中，我们调查了CT的这一特性是否与对B细胞同种型分化的影响有关。最初，我们确定了CT对正常LPS诱导的派尔集合淋巴结B细胞的影响，发现虽然CT强烈抑制IgM的产生，但它使产生IgG和IgA的细胞数量和频率增加了约三倍。随后，使用细胞分选技术，我们证明CT作用于膜（m）IgM +、mIgG/mIgA - B细胞，而不是mIgG/mIgA + B细胞。此外，我们表明CT不会导致mIgM的选择性抑制，也不会增强mIgG/mIgA B细胞的增殖。在平行研究中，我们确定了CT对克隆B细胞群体CH12.LX细胞分化的影响，即主要由mIgM +细胞（98%）与一小部分mIgA +细胞（2%）混合组成的群体。在这里，我们发现CT（在没有LPS的情况下）会导致mIgM表达强度迅速下降（24小时），以及表达mIgA的亚群大小显著增加。此外，我们发现CT（在有LPS的情况下）抑制CH12.LX IgM的产生，同时增加产生IgA的细胞的绝对数量和频率。相反，CT抑制CH12.LX.A2细胞（CH12.LX细胞的一个亚克隆，仅携带IgA）产生IgA。最后，我们证明CT对CH12.LX细胞和CH12.LX.A2细胞的增殖具有同等的抑制作用。综上所述，CT对正常B细胞和克隆B细胞系的这些作用表明，CT诱导大量mIgM +细胞经历同种型分化为mIgG +或mIgA + B细胞。在最后一系列研究中，我们表明CT对同种型分化的作用被CT的B亚基模拟，即不激活细胞内腺苷酸环化酶的亚基；因此，CT诱导的同种型分化不是由cAMP水平的扰动介导的。
