Suppressor cells in Lewis rats with experimental allergic encephalomyelitis: prevention of the disease and inhibition of lymphocyte proliferation by the suppressor cells or their products.

Lewis rats primed with myelin basic protein (MBP) in complete Freund's adjuvant develop experimental allergic encephalomyelitis (EAE) and suddenly recover 15 to 17 days later. It was previously found that nondraining lymph node (non-DLN) cells taken at the time of convalescence and transferred into syngeneic normal animals inhibit the subsequent induction of EAE. In this report, it is shown that a suppressive factor can be extracted from non-DLN cells which mimics the inhibitory effect of cells when injected into the recipients. Non-DLN cells keep their suppressive activity on the induction of EAE after a culture of 48 h but their supernatant of culture failed to exert any protective effect in vivo. However, in vitro both the culture supernatant and the suppressor cells were found to have an inhibitory effect on the proliferative response of immune lymphoid cells to the antigen (MBP).