Tony H P, Phillips N E, Parker D C
J Exp Med. 1985 Nov 1;162(5):1695-708. doi: 10.1084/jem.162.5.1695.
Resting murine B lymphocytes can present rabbit anti-Ig to T cell lines specific for normal rabbit globulin. The T cell-B cell interaction is major histocompatibility complex (MHC)-restricted, and leads to activation, proliferation, and differentiation of the resting B cell into an antibody-secreting cell. Efficient antigen presentation and B cell activation depends upon binding of rabbit globulin to (membrane) mIg. To investigate the role of mIg in this polyclonal model for a T cell-dependent primary antibody response, we determined whether crosslinking of mIg is required either for efficient antigen presentation, as measured by helper T cell activation, or for the B cell response to T cell help, since all the direct effects of anti-Ig on B cells require crosslinking of mIg. We found that monovalent Fab' fragments of anti-IgM or anti-IgD work as efficiently as their divalent counterparts. Therefore, a signal transduced through the antigen receptor seems not to be required when T cell help is provided by an MHC-restricted T helper cell recognizing antigen on the B cell surface. Moreover, rabbit globulin bound to class I MHC molecules in the form of anti-H-2K also results in efficient antigen presentation and T cell-dependent B cell activation. However, mIg still appears to be specialized for antigen presentation, since anti-Ig is presented about three- to fivefold more efficiently than anti-H-2K.
静息的小鼠B淋巴细胞能够将兔抗Ig呈递给对正常兔球蛋白特异的T细胞系。T细胞与B细胞的相互作用受主要组织相容性复合体（MHC）限制，并导致静息B细胞激活、增殖并分化为抗体分泌细胞。高效的抗原呈递和B细胞激活取决于兔球蛋白与（膜）mIg的结合。为了研究mIg在这种T细胞依赖性初次抗体应答的多克隆模型中的作用，我们确定，对于通过辅助性T细胞激活来衡量的高效抗原呈递，或者对于B细胞对T细胞辅助的应答而言，mIg的交联是否是必需的，因为抗Ig对B细胞的所有直接作用都需要mIg的交联。我们发现，抗IgM或抗IgD的单价Fab′片段与它们的二价对应物一样有效。因此，当由识别B细胞表面抗原的MHC限制的辅助性T细胞提供T细胞辅助时，似乎不需要通过抗原受体转导信号。此外，以抗H-2K形式与I类MHC分子结合的兔球蛋白也能导致高效的抗原呈递和T细胞依赖性B细胞激活。然而，mIg似乎仍专门用于抗原呈递，因为抗Ig的呈递效率比抗H-2K高约三至五倍。
