Topographical Distribution of T Cells in Lymphatic Organs of B Rat : Immunoperoxidase Study

Inbred PVG/c strain rats were thymectomized 3-4 weeks after birth. Later, usually a few weeks, the rats were lethally irradiated and then reconstituted with bone marrow cells from syngeneic donors. Rats that have been subjected to this procedure are tentatively called ”B” rats in the present study. The topographical distribution of T cells in the lymphatic tissues of B rats was studied by the indirect immunoperoxidase staining using anti-T cell monoclonal antibody. This technique clearly showed the T cells in the paraffin sections of Carnoy-fixed tissue. Results obtained are as follows. 1. The deep cortex in the lymph nodes and the periarterial lymphoid sheath of the spleen were depleted of small lymphocytes. 2. However, a considerable number of T cells were found in these areas. 3. Such depletion of T cells in the lymphatic tissues were nearly restored to its normal level by transfusion of syngeneic thymocytes. In addition, the origin of T cells in the lymphatic tissues of B rats was discussed. These T cells seem to be derived from both the host and donor. However, the origin is still unsettled.