Studies on experimental autoimmune thymitis in guinea-pigs

Abstract

Normal and thymectomized outbred guinea-pigs were immunized with extracts of calf thymus, calf skeletal muscle or calf heart muscle emulsified in Freund's complete adjuvant. Immunization with either thymus or skeletal muscle produced a significant incidence of thymitis and a partial neuromuscular block in contrast to control animals either untreated or injected with an extract of calf lymph node or saline in Freund's complete adjuvant. The incidence of thymitis and partial neuromuscular block in animals that were injected with an extract of calf heart muscle in Freund's complete adjuvant was found not to be significant when compared to the control animals.

Neuromuscular transmission was studied using Copeland–Davis clip electrodes or a bipolar silver wire electrode threaded through the flexor digitorum muscle. The development of partial neuromuscular block in the test animals was found to be dependent on the presence of the thymus. All animals with a partial neuromuscular block had evidence of experimental thymitis.

These findings are in keeping with the hypothesis that a factor released by the thymus may be important in the development of the neuromuscular block characteristic of myasthenia gravis.