Supplementary Studies on Postnatal Histogenesis of Thymolymphatic Tissues of Albino Rats II. Age Changes in Plasma Cell Occurrence.

It was shown in the previous paper that in the rat peripheralization of lymphoid organs started in about 3 weeks of age.An appearance of plasma cells-antibody producer is also considered to be an important factor of the peripheralization.In the present study, an initial appearance of plasma cells and futher changes in the cells in response to aging were studied in the same material as used in the previous report.The chief findings are shown in the table 1 and fig.1.Plasma cells were first noted at the 2nd week in the mesenteric lymph nodes, at the 4th week in the spleen, and at the 2nd month in the thymus.Thereafter, the average values of number of plasma cells showed a gradual increase, reaching the maximum at the 6th month of age.After this period the values showed a progressive decrease.It is of interest that in the rat the initial appearance of plasma cells agrees practically with the time of peripheralization of the lymphatic tissue in the mesenteric lymph nodes and spleen.