RESUMO
The following experiment was performed to clarify distributional changes of the Ly1, L3T4, Ly2 positive T cells and IgM positive B cells 1, 4, 8, 12 and 40 weeks after birth. Thymus, spleen and lymph node were removed and immunohistochemical staining such as avidin -biotin -peroxidase complex method was used. The results obtained from above epxperiment were as follows; 1. Ly1 positive T cells were decreased after 8 weeks in the thymus and spleen. these were decreased after 40 weeks in the lymph node. 2. There was no difference L3T4 positive T cells in the thymus, but in the spleen decrease of cell number was shown after 40 weeks. 3. Ly2 postive T cells were decreased after 4 weeks in the thymus, after 40 weeks in the spleen. There was no change of distribution in the lymph node. 4. There was no difference distribution of IgM positive B cells. The results suggest that the age related decrease of the immunity is caused by decrease of cellular immunity related to T cell depletion.