Studies on the germinal center

Summary Ultrastructure of mitotic cells in human lymph node germinal centers was deliberately studied in contrast to that of plasma cells in mitosis which were rarely found in medullary cords or lymphatic sinuses of the same materials. It was demonstrated that the mitotic cells in germinal centers are evidently different from the latter in the absence of lamellary arranged endoplasmic reticulum with ribosomes and Golgi apparatus, and are quite similar to the ultrastructure of thymic lymphocytes in mitosis reported by Murray et al. It should be concluded from these findings that the cells produced locally within the germinal centers in human lymph nodes are lymphocytic as has been repeatedly suggested by the authors.Supported by Grant in Aid from the Ministry of Education of Japan (69-9254).