Immunoregulatory circuits which modulate responsiveness to suppressor cell signals: contrasuppressor cells can convert an in vivo tolerogenic signal into an immunogenic one.

The intravenous injection of 2,4,6-trinitrophenyl (TNP)-labeled peritoneal exudate cells (TNP-PEC) into CBA mice fails to produce a state of hypersensitivity; rather, it renders recipient mice incapable of mounting a contact hypersensitivity response when they are subsequently immunized with a reactive form of the specific hapten. However, if precultured neonatal spleen cells are injected along with the cells that induce tolerance (TNP-PEC), not only is the development of tolerance inhibited but sensitization to TNP develops. The neonatal spleen cell responsible for turning the tolerogenic signal into an immunogenic one is I-J+ and adheres to the Vicia villosa lectin. Thus, it expresses markers that distinguish contrasuppressor effector cells from helper cells (D. R. Green et al., Eur. J. Immunol. 1981. 11:973), indicating that activated contrasuppressor cells can act as potent, helpful regulatory cells in vivo.