Mycobacterial Suppression of Delayed Hypersensitivity in Experimental Allergic Encephalomyelitis

Experimental allergic encephalomyelitis, induced by injection of myelin basic protein in Freund's adjuvant, can be suppressed either by pretreatment with Freund's adjuvant alone (heat-killed mycobacteria in an oil—Aquaphor emulsion) or by addition of extra heat-killed mycobacteria to the encephalitogenic emulsion. Suppression of disease is accompanied by disappearance of skin reactivity to myelin basic protein. No circulating antibody to BP was detected in the sera of the suppressed animals prior to or at any time up to 26 days after challenge. Thus the suppression of delayed hypersensitivity noted in the present experiments cannot be attributed to presence of circulating antibody to myelin basic protein. Simultaneous suppression of skin sensitivity and CNS lesions strengthens the hypothesis that the two phenomena are related manifestations of delayed hypersensitivity.