Effects· of the Azathioprine Administered during Pregnancy on the Lymphoid Orga n s of the Neonatal Rats.

The following experiment was performed to study the effect of azathioprine administered during pregn' ancy on the development of lymphoid organs of neo' natal rats. The experimental animals were the three hundred Sprague·Dawley neonatal rats which were divided into four groups. The animals born from the azathioprine' administered adults during pregnancy were named for group 1 and 2. and were injected with antigen to group 1 and saline to group 2 respectively after birth. The animals of group 3 and 4 were born from the adults free of azathioprine during pregnancy and were injected with antigen to group 3 and saline to group 4 respectively after birth. Antigen or saline was injected intraperitoneally on the 1st. 4th. 9th. 12th and 16th week after birth. Then the spleen and thymus were resected on the 1st. 3rd. and 7th day after the injection for the plaque assay and histochemical studies The following results were obtained: 1. No plaque·forming cells and large pyroninophilic cells were observed in the spleens of all groups on the first week after birth 2. The number of plaque·forming cells and large pyroninoph i1ic cells observed in the spleens was much less after antigen injection but a little less after saline injection in the group of azathioprine admini stration than in the control group on the 4th. 8th and 12th week after birth. 3. A similar number of many plaque·forming cells and large pyroninophi1ic cells were observed in the all groups on the 16th week after birth. 4. While the development of thymus was retMded histologically for the groups of azathioprme acimini· stration than the control groups until the· 8th week after birth. a similar development of thymus between the two groups was observed on the 12th and 16h week after birth. 5. It may be suggested that adminislration of azathioprine did interfere with the development of T·lymphocyte and censequently affected the formation of antibody due to the insu뻐cient collaboration between T cells and B cells