抄録
Effect of long-lasting suppression of the thymic lympho-poiesis on the development of the splenic lymphoid components was investigated using male white leghorn chickens. The thymic lobes of young chickens were kept rudimentary and alymphocytic by an exposure to 650 r of whole body X-irradiation at one day of age and subsequent repeated exposures of the neck to 650 r X-rays. The bursae showed no morphological evidence of damage to the lymphopoietic activity. In the spleens, a near-complete loss of the small lymphocyte population and a marked suppression of the germinal center formation were observed, while the periellipsoidal lymphoid tissue and the plasma cell series, both being the bursa-dependent elements, were well developed. Lymphocytic repopulation in the thymus after the termination of the repeated X-irradiations was followed by the appearance: of small lymphocytes and the development of germinal centers in the spleen. These observations lead us to conclude that the germinal center formation in chickens is not merely a bursa-dependent process but may be influenced by certain thymus-dependent factor or factors.
