HELPER FUNCTIONS OF ANTIGEN-INDUCED SPECIFIC AND AUTOREACTIVE T-CELL COLONIES

  • 1 January 1984
    • journal article
    • research article
    • Vol. 1  (2) , 65-73
Abstract
Helper T cells are distinguished on the basis of whether the provide carrier-specific or nonspecific helper functions. It has been determined that the predominant class of helper T cell in populations of primed lymph node cells is a nonspecific helper T cell unable to provide carrier-specific signals. Initial induction of nonspecific helper T cells in vitro requires restimulation with the immunogen. This suggested that such T cells may express antigen-specific receptors. In this case they would constitute a unique subpopulation distinct from T cells with identical antigen-specificity that are able to provide carrier-specific help. Alternatively, the requirement for antigen restimulation might reflect a role for antigen-specific T cells in the recruitment of T cells with unrelated specificity. To distinquish between these possibilities, the specificity and function of [mouse] helper T cell colonies selected from primed lymph node cells were characterized. Isolation of autoreactive as well as antigen-specific helper T cells is reported. All antigen-specific T cell colonies provide carrier-specific help in the presence of the homologous hapten-carrier conjugate. Only autoreactive T cells are limited to providing nonspecific helper function. Although selection of autoreactive T cells is initially dependent on antigen restimulation in vitro, activation of an established autoreactive T cell line requires restimulation with MHC [major histocompatibility complex]-syngeneic spleen cells but does not require stimulation with either the immunogen or fetal calf serum. The results suggest that nonspecific helper T cells induced in the course of a normal immune response to randomly chosen foreign antigens are autoreactive. Such T cells may serve to enhance proliferation and maturation to Ig secretion of B cells activated by limiting numbers of carrier-specific helper T cells. The demonstration of large numbers of precursors to MHC-specific autoreactive T cells in antigen-primed populations raises important issues concerning regulation of the expansion of autoreactive T cells in vivo.

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