Chen J C, Leon M A
J Immunol. 1976 Feb;116(2):416-22.
Normal and congenitally athymic mice respond to immunization with dextran, thus indicating that the response is thymus independent. Athymic mice have lower plaque-forming cell (PFC) response than normal mice 3 days after immunization, but similar PFC response as normal mice by 5 days. Seven to 10 days after immunization, athymic mice maintain a high level of PFC response whereas the PFC response declines sharply in normal mice. Concanavalin A (Con A), added at initiation of in vitro culture, enhances the response of spleen cells from primed normal mice. Treatment with methyl-alpha-D-mannoside (MAM), a competitive inhibitor of binding of Con A, immediately after addition of Con A, abolishes the enhancement. Treatment with MAM, 3 to 6 hr after Con A addition, partially blocks the enhancement. The enhancing effect is dependent on the dose of Con A and the duration of in vivo priming before in vitro culture. Con A does not enhance the in vitro PFC response of cells from primed athymic mice. Supernatants from Con A-treated non-primed normal spleen cell cultures enhance the PFC response of "nude" cells, thereby indicating that enhancement by Con A is mediated through a soluble T cell product(s) with no apparent antigen specificity. Hydroxyurea, an inhibitor of DNA synthesis, blocks the enhancement by Con A of cells primed for 1 to 3 days. Release of hydroxyurea block after 19 hr incubation does not restore the PFC response, thereby indicating the responding anti-dextran PFC precursor cells are engaging actively in DNA synthesis. PFC response of primed cells taken at the peak of anti-dextran response (day 5) shows that they are less susceptible to the hydroxyurea block. Con A enhances the PFC response of cells primed for 5 days even in the absence of DNA synthesis.
正常小鼠和先天性无胸腺小鼠对右旋糖酐免疫均有反应，这表明该反应不依赖胸腺。免疫后3天，无胸腺小鼠的空斑形成细胞（PFC）反应低于正常小鼠，但到5天时其PFC反应与正常小鼠相似。免疫后7至10天，无胸腺小鼠维持高水平的PFC反应，而正常小鼠的PFC反应则急剧下降。在体外培养开始时添加刀豆球蛋白A（Con A），可增强经致敏的正常小鼠脾细胞的反应。添加Con A后立即用Con A结合的竞争性抑制剂α-D-甘露糖苷（MAM）处理，可消除这种增强作用。添加Con A后3至6小时用MAM处理，可部分阻断这种增强作用。增强作用取决于Con A的剂量和体外培养前体内致敏的持续时间。Con A不会增强经致敏的无胸腺小鼠细胞的体外PFC反应。Con A处理的未致敏正常脾细胞培养物的上清液可增强“裸”细胞的PFC反应，从而表明Con A的增强作用是通过一种无明显抗原特异性的可溶性T细胞产物介导的。DNA合成抑制剂羟基脲可阻断Con A对致敏1至3天细胞的增强作用。孵育19小时后解除羟基脲阻断并不能恢复PFC反应，这表明反应性抗右旋糖酐PFC前体细胞正在积极参与DNA合成。在抗右旋糖酐反应高峰期（第5天）采集的致敏细胞的PFC反应表明，它们对羟基脲阻断的敏感性较低。即使在没有DNA合成的情况下，Con A也可增强致敏5天细胞的PFC反应。
