Autoimmune diseases and thalidomide. I. Experimental allergic encephalomyelitis and experimental allergic neuritis of the guinea pig.

The teratogenic effect of thalidomide (Th) is well-known. Current theories about the mechanism of action of this effect have been well summarized by Woollam (21), There is controversy about the possible immunosuppressive action of this compound (1 , 2,4,5, 10) and its influence on chromosome aberrations (9. 14. 15). It seems clear, however, that the drug does not have an all-inclusive "blanket" effect over immune responses. Thalidomide is very active, sometimes dramatically so, on signs and symptoms of reactional lepromatous leprosy (3). It does not have, however, any direct effect over Mycobacterium leprae and cannot be considered as an anti-leprosy drug (16). Reactional lepromatous leprosy has many clinical and histologic features of hypersensitivity reactions as has been stressed recently (20). We decided to explore the possibility of a suppressive effect of this drug over autoimmune experimental diseases, in which delayed hypersensitivity is all important, and where tissue components and mycobacteria have to be administered together as they occur, for instance, in lepromatous neuritis. In a first series of experiments, experimental allergic encephalomyelitis ( EAE ) and experimental allergic neuritis (EAN)