Humoral and cell-mediated immune responses of Lewis rats to syngeneic basic protein of myelin

In Lewis rats, injection of syngeneic basic protein of myelin with Freund’s complete adjuvant and pertussis vaccine induced clinical and histological signs of experimental autoimmune encephalomyelitis (EAE), humoral antibody, and cell-mediated immunity to the basic protein. Antigenic cross reactivity between the encephalitogenic basic proteins of rat and human was demonstrated. Injection into Lewis rats of graded doses of rat or human basic protein induced dose-related levels of serum antibody and severity of EAE. In growing rats, low doses of rat basic protein (0.1–1.0 µg) did not induce clinical or histological signs of EAE, nor detectable serum antibody, but did induce loss of weight. In rats receiving larger doses of basic protein, weight loss was marked, and the mean levels of serum antibody rose abruptly when the rats began to regain weight. A possible function in vivo of serum antibody to myelin basic protein may be to reestablish immunological tolerance to the basic protein at the level of the immunocompetent cell; the amount of antibody required to restore tolerance may depend on the dose of immunogen used to initiate the autoimmune response.