Conley M E, Bartelt M S
J Immunol. 1984 Nov;133(5):2312-6.
In vitro regulation of IgA subclass synthesis was investigated in pokeweed mitogen (PWM)-stimulated cultures of peripheral blood lymphocytes. In past experiments we have demonstrated that 50% of the IgA plasma cells derived from PWM-stimulated cultures are positive for IgA1 and 50% are positive for IgA2. This observation is surprising because approximately 80% of the IgA B cells in the peripheral circulation bear IgA1 and 20% bear IgA2. To determine if the shift toward IgA2 predominance in PWM-stimulated cultures might be due to an enriched source for IgA2 plasma cells from a precursor pool of immature B cells, we used panning techniques to separate immature precursors that express surface IgM (sIgM+) from mature precursors that no longer express IgM (sIgM-). These separated B cells were cultured with equal numbers of T cells and PWM for 7 days. In all 10 experiments there was an enrichment for IgA2 in the sIgM+ cultures; 55 +/- 9.6% of the total IgA plasma cells were positive for IgA2 in the sIgM+ cultures vs 38 +/- 6.3% in the sIgM- cultures (p less than 0.001). These results indicate that both sIgM+ and sIgM- cells can give rise to IgA plasma cells in PWM-stimulated cultures and that there is an enrichment for IgA2 precursors in the sIgM+ population. Other possible regulatory mechanisms were also investigated. To determine if there was isotype switching from IgA1 to IgA2, monoclonal anti-IgA1 antibodies were added to PWM cultures. These antibodies resulted in a mean suppression of IgA1 plasma cell production of 82% with a concomitant 45% suppression of total IgA but only 4.6% suppression of IgA2. These results make it unlikely that IgA2 plasma cells in PWM-stimulated cultures are derived from cells that initially produced IgA1. To investigate the possibility that one IgA subclass might be more T cell dependent than the other, T and B cells were separated and B cells were reconstituted with T cells in ratios that varied from 1:10 to 10:1 or with irradiated T cells. These procedures did not alter the proportion of IgA plasma cells positive for IgA1 or IgA2, indicating that the two subclasses do not differ in their response to T cell signals in PWM-stimulated cultures.
在体外研究了美洲商陆丝裂原（PWM）刺激的外周血淋巴细胞培养物中IgA亚类合成的调节情况。在过去的实验中，我们已经证明，源自PWM刺激培养物的IgA浆细胞中，50%对IgA1呈阳性，50%对IgA2呈阳性。这一观察结果令人惊讶，因为外周循环中约80%的IgA B细胞携带IgA1，20%携带IgA2。为了确定在PWM刺激的培养物中向IgA2优势的转变是否可能是由于来自未成熟B细胞前体池的IgA2浆细胞来源丰富，我们使用淘选技术将表达表面IgM（sIgM+）的未成熟前体与不再表达IgM（sIgM-）的成熟前体分离。将这些分离的B细胞与等量的T细胞和PWM一起培养7天。在所有10个实验中，sIgM+培养物中IgA2都有富集；sIgM+培养物中总IgA浆细胞的55±9.6%对IgA2呈阳性，而sIgM-培养物中为38±6.3%（p<0.001）。这些结果表明，在PWM刺激的培养物中，sIgM+和sIgM-细胞都可以产生IgA浆细胞，并且sIgM+群体中IgA2前体有富集。还研究了其他可能的调节机制。为了确定是否存在从IgA1到IgA2的同种型转换，将单克隆抗IgA1抗体添加到PWM培养物中。这些抗体导致IgA1浆细胞产生平均抑制82%，同时总IgA抑制45%，但IgA2仅抑制4.6%。这些结果表明PWM刺激培养物中的IgA2浆细胞不太可能源自最初产生IgA1的细胞。为了研究一种IgA亚类可能比另一种更依赖T细胞的可能性，将T细胞和B细胞分离，并以从1:10到10:1的不同比例用T细胞或照射过的T细胞重建B细胞。这些操作没有改变对IgA1或IgA2呈阳性的IgA浆细胞的比例，表明在PWM刺激的培养物中，这两个亚类对T细胞信号的反应没有差异。
