Unresponsiveness to experimental allergic encephalomyelitis in mice: replacement of suppressor cells by a soluble factor.

A soluble suppressor factor has been prepared from cells of mice rendered nonsusceptible to experimental allergic encephalomyelitis (EAE) by treatment with mouse spinal cord homogenate in incomplete Freund's adjuvant. The specific activity of this factor can be augmented by using a cell population enriched on plates coated with anti-mouse Fab and the specific antigen, mouse basic encephalitogen (MBE). The resultant suppressor factor had the same biologic activities as the cells from which it originated. Thus, it suppressed specifically the delayed-type hypersensitivity (DTH) response to MBE in vivo, and blocked in vitro the effector lymphocytes that adoptively transfer the DTH response. The suppressor factor reactivity was manifested also by the capacity to suppress the activity of macrophage migration inhibition factor produced by sensitized lymphocytes in the presence of the specific antigen MBE. The suppressor factor is antigen-specific and can bind the MBE in vitro and thus compete with its antibody binding. The most significant activity of the soluble suppressor factor is its ability to interfere with the induction of clinical EAE.