The spleen is required for the suppression of experimental allergic encephalomyelitis by prostaglandin precursors.

In this paper we report a study of the effects of splenectomy on the immunosuppressive action of essential fatty acids (EFA) which is thought to be mediated through prostaglandins (PG) produced in the spleen. Experimental allergic encephalomyelitis (EAE) was induced in normal, splenectomized and sham splenectomized Lewis rats. EFA were administered orally, the animals in the control groups being treated with liquid paraffin. Treatment with EFA significantly suppressed clinical disease in those animals in which EAE was induced by the inoculation of central nervous system material of guinea-pigs or by passive transfer by Con A-stimulated spleen cells. Splenectomy abrogated the suppressive effect of EFA. This observation, together with previous results showing the abrogation of EFA immunosuppression by an inhibitor of the biosynthesis of PG from EFA, led us to postulate a close relationship between EFA, PG and a splenic factor suppressing immunopathological mechanisms in EAE.