Formation of Germinal Centers in the Rat Thymus
Rats of Wistar strain were given 20 intraperitoneal injections of a saline suspension of typhoid-paratyphoid bacilli (3 × 108) plus serotonin (serotonin Creatinin sulfate 0.25 mg) at 10 day intervals. A large number of thymic germinal centers were formed in females, but not in males. However, orchidectomy induced the formation of germinal centers in the thymus of males as well as females. No thymic germinal centers were formed after injections of either typhoid-paratyphoid bacilli or serotonin only.