Pascual D W, Xu-Amano J C, Kiyono H, McGhee J R, Bost K L
Department of Microbiology, University of Alabama, Birmingham 35294.
J Immunol. 1991 Apr 1;146(7):2130-6.
The IgA producing murine B lymphoma, CH12.LX.C4.4F10 (4F10) and the IgM producing murine lymphoma, CH12.LX.C4.5F5 (5F5) were found to express substantial numbers of substance P (SP) receptors having dissociation constants equal to 0.69 nM. Binding of SP by these B lymphoma cells was via the tachykinin-specific C-terminus sequence, Phe-X-Gly-Leu-Met-NH2, because SP, SP antagonist (D-Pro2-D-Phe7-D-Trp9-SP), eledoisin, and substance K could effectively inhibit radiolabeled SP binding, whereas the SP N-terminus fragment, SP (1-4), could not. The functionality of these receptors could be demonstrated by the ability of subnanomolar concentrations of SP to induce Ig secretion in a dose-dependent fashion. However, the presence of a second stimulus in these cultures was required to obtain maximal increases. IgA secretion by 4F10 cells was elevated only 25 to 37%, and IgM secretion by 5F5 cells was not significantly increased in cultures in which nanomolar concentrations of SP were present. Conversely, coculturing 5F5 cells with a suboptimal concentration of LPS (50 ng/ml) and 10(-10)M SP resulted in an approximate threefold increase in supernatant IgM when compared to control cultures stimulated with LPS alone. While not as dramatic, 10(-10) M SP also enhanced IgA secretion of LPS-stimulated 4F10 cells by approximately 45%. This enhancement of Ig secretion was SP-specific, as evidenced by the ability of 1000-fold excess of SP antagonist to block SP-induced, but not LPS-induced, Ig production. Clearly, SP could act synergistically with LPS to enhance Ig secretion; therefore, we questioned whether this augmentation was also reflected at the level of H chain mRNA expression. 10(-9)M SP induced modest increases (50 to 60%) in mu-chain mRNA expression by LPS-stimulated 5F5 cells when compared with cells stimulated with LPS alone. The 4F10 cells did not display this magnitude of difference for alpha-chain mRNA expression. Thus, although SP-induced increases of mu-chain mRNA by 5F5 cells may contribute to the increased Ig secretion observed by these LPS-activated lymphocytes, it is unlikely that increased mRNA expression can totally account for the threefold increases in secretion that were observed.
已发现产生IgA的小鼠B淋巴瘤细胞CH12.LX.C4.4F10（4F10）和产生IgM的小鼠淋巴瘤细胞CH12.LX.C4.5F5（5F5）表达大量解离常数等于0.69 nM的P物质（SP）受体。这些B淋巴瘤细胞对SP的结合是通过速激肽特异性C末端序列Phe-X-Gly-Leu-Met-NH2进行的，因为SP、SP拮抗剂（D-Pro2-D-Phe7-D-Trp9-SP）、eledoisin和物质K可有效抑制放射性标记的SP结合，而SP的N末端片段SP（1-4）则不能。这些受体的功能可通过亚纳摩尔浓度的SP以剂量依赖性方式诱导Ig分泌的能力来证明。然而，这些培养物中需要存在第二种刺激才能获得最大程度的增加。在存在纳摩尔浓度SP的培养物中，4F10细胞的IgA分泌仅升高25%至37%，5F5细胞的IgM分泌没有显著增加。相反，将5F5细胞与次优浓度的LPS（50 ng/ml）和10^(-10)M SP共培养，与仅用LPS刺激的对照培养物相比，上清液中的IgM增加了约三倍。虽然效果不那么显著，但10^(-10)M SP也使LPS刺激的4F10细胞的IgA分泌增加了约45%。这种Ig分泌的增强是SP特异性的，1000倍过量的SP拮抗剂能够阻断SP诱导而非LPS诱导的Ig产生就证明了这一点。显然，SP可与LPS协同作用以增强Ig分泌；因此，我们质疑这种增强是否也反映在重链mRNA表达水平上。与仅用LPS刺激的细胞相比，10^(-9)M SP使LPS刺激的5F5细胞的μ链mRNA表达适度增加（50%至60%）。4F10细胞在α链mRNA表达上没有显示出如此大的差异。因此，尽管5F5细胞中SP诱导的μ链mRNA增加可能有助于这些LPS激活的淋巴细胞中观察到的Ig分泌增加，但mRNA表达增加不太可能完全解释所观察到的分泌增加三倍的情况。
