Farrar J J, Fuller-Bonar J
J Immunol. 1976 Jul;117(1):274-82.
Studies were conducted on the mechanism of action of a soluble mediator which was generated in human mixed lymphocyte cultures and assayed for helper activity in T cell-deficient murine spleen cell cultures. The mediator, termed xenogeneic reconstitution factor or XFR, restored the anti-sheep erythrocyte plaque-forming cell response of spleen cells from thymectomized, lethally irradiated, and syngeneic bone marrow transplated (TxB) mice. It was found that in order to obtain a maximal antibody response, the XRF had to be present sometime during the first 24 to 40 hr of the induction process. XRF was also required during the last 24 hr of the incubation period. A striking synergistic effect was obtained by combined exposure of the T cell-deficient spleen cell cultures to XRF during the first and last days of culture. These data suggested a bi-modal mechanism of action of XRF, and raised the possibility that in addition to providing a signal to the B cells, XRF-mediated activation of the residual TxB splenic T cells was crucial to the successful restoration of the antibody response. Treatment of the nonadherent splenocytes from the TxB mice with anti-T cell serum and guinea pig complement completely abrogated the antibody response of these cells in the presence of adherent spleen cells, sheep erythrocytes, and the helper factor XRF. The antibody response of this combination of cells, antigen, and XRF was reconstituted by a population of unimmunized murine T cells which, in the absence of XRF, were totally unable to restore responsiveness. These results suggest that B cell activation to the formation of antibody involves the mandatory co-participation of two functionally distinct helper activities.
对一种可溶性介质的作用机制进行了研究，该介质是在人混合淋巴细胞培养物中产生的，并在T细胞缺陷的小鼠脾细胞培养物中检测其辅助活性。这种介质被称为异种重建因子或XFR，它恢复了来自经胸腺切除、致死性照射和同基因骨髓移植（TxB）小鼠的脾细胞对绵羊红细胞的空斑形成细胞反应。研究发现，为了获得最大的抗体反应，XRF必须在诱导过程的最初24至40小时内的某个时间存在。在培养期的最后24小时也需要XRF。通过在培养的第一天和最后一天将T细胞缺陷的脾细胞培养物联合暴露于XRF，获得了显著的协同效应。这些数据提示了XRF的双相作用机制，并提出了一种可能性，即除了向B细胞提供信号外，XRF介导的残余TxB脾T细胞的激活对于抗体反应的成功恢复至关重要。用抗T细胞血清和豚鼠补体处理TxB小鼠的非贴壁脾细胞，在存在贴壁脾细胞、绵羊红细胞和辅助因子XRF的情况下，完全消除了这些细胞的抗体反应。一组未免疫的小鼠T细胞重建了这种细胞、抗原和XRF组合的抗体反应，而在没有XRF的情况下，这些T细胞完全无法恢复反应性。这些结果表明，B细胞激活形成抗体涉及两种功能不同的辅助活性的强制性共同参与。
