Immunosuppression by cell-free translation products from monoclonal antigen-specific suppressor T cell mRNA.

Polypeptides synthesized in a rabbit reticulocyte lysate system directed by mRNA from the T cell line LH8-105, obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (HEL)-specific suppressor T lymphocytes, are able, when injected into mice, to specifically suppress the antibody response and delayed-type hypersensitivity to HEL. The suppressive activity exerted by in vitro translated proteins appears to be independent from post-translational modifications. These in vitro translated polypeptides display fine antigenic specificity in immunosuppression and bind to HEL but not to the closely related ring-necked pheasant egg-white lysozyme immunosorbents. Suppressive molecules obtained by cell-free translation of LH8-105 mRNA or by culture supernatant of LH8-105 cells display, by gel filtration, a similar molecular mass of about 82-90 kDa.