Abstract
On the dd strain mice thymectomized within 24 hours after birth, were examined immune response to various antigenic stimulations and acquisition of non-specific resistance following the administration of zymosan, and the following results were obtained.
1. Impairment of the primary as well as the secondary antibody responses to sheep erythrocyte, heatkilled salmonella and T2-phage antigens was noticed in the neonatally operated mice.
2. When ascites hepatoma cells of AH39 strain indigenous to rat were inoculated intraperitoneally into the thymectomized mice, the xenogeneic grafts multiplied flourishly in the peritoneal cavity leading to the death of the host. On the contrary, in the non-thymectomized control animals, the inoculated tumor cells were rejected entirely within 7 to 12 days after the transplantation.
3. The presence of the thymus seemed to be essential for the normal development of the acquired resistance to experimental typhoid and toxoplasmosis after immunization with attenuated live vaccines.
4. Even on the neonatally thymectomized mice, non-specific resistance was conferred after the admi-nistration with zymosan. Thus, the thymectomized mice, which had been administered with zymosan 1 to 14 days prior to the infection, resisted to an intraperitoneal pneumococcal infection. As a concomitant of this non-specific resistance, increase of acid phosphatase activities was obtained in the peritoneal exudate cells of these animals.
