Lymphocyte response depressive factor in multiple sclerosis.

Normal serum contains a lymphocyte response depressive factor and this is more active against the lymphocytes of the blood from which the serum was obtained than against lymphocytes from a different normal blood. The suppressive factor is thus "tailor-made" to its own lymphocytes though cross-reactivity with other lymphocytes does occur. The significance of this is discussed. The suppressive factor has a higher titre in serum from patients with multiple sclerosis or other destructive neurological disease than in normal serum. This may be an instance of a general phenomenon in which lymphocyte sensitization is ordinarily accompanied by production of a suppressor factor able to damp down response so that this is controlled by an "acceleratorbrake" mechanism. The possibilities of imbalance in the pathogenesis of disease and therapeutic manipulation of the level of suppressor substance are briefly discussed.