Suppressor activity of splenocytes from mice treated with Ecteinascidia turbinata extract.

Extracts of a marine tunicate, Ecteinascidia turbinata (Ete) were previously shown to be capable of suppressing humoral and cellular immune responses in vivo and in vitro. In the present work we have examined the mechanisms of suppression in Ete-treated DBA/2 and BALB/c mice. Treatment with Ete resulted in a significant splenomegaly accompanied by a diminished response to mitogenic stimulation, reaching coincident maxima of effect at days 4 to 6. Spleen size and blastogenic reaction returned to normal at 12 to 21 days. Cells from enlarged spleens inhibited blastogenic responses of normal splenocytes to Con A. Marker studies indicated that the suppressor activity was exerted by cells possessing T lymphocyte characteristics.