Linomide, a synthetic quinoline carboxamide, has the ability to stimulate various lymphocyte subpopulations. We have shown its inhibitory effect on the clinical and histological signs of acute and chronic relapsing EAE. In these models linomide induces suppression of lymphocyte response to antigens, production of autoantibody, antigen presentation to specific T-cell lines and Mac-I expression, and induces activation of NK and suppressor-inducer cells. We have subsequently shown its inhibitory effect on clinical and MRI signs of patients with secondary progressive multiple sclerosis. Results of a double blind, placebo controlled, short term pilot study with p.o. linomide, showed a significant effect on the clinical disability scale (EDSS) (P = 0.045) and on the mean total number of new lesions in serial monthly MRI scans (P = 0.021). The increase of CD45Ra, CD8 and CD16 positive cells in linomide treated patients may indicate the importance of suppressor-inducer, suppressor and NK cells for the inhibition of the autoimmune response in the disease.