[Cytochemical differentiation of T- and B-lymphocytes in the short-tailed mouse (Clethrionomys glareolus)]

Using the cytochemical demonstration of alkaline phosphatase (AP) two different populations of lymphocytes are seen in the short-tailed mouse Clethrionomys glareolus: AP-positive and PA-negative lymphocytes. The aim of this study was to find out as to whether in this species AP represents a cytochemical marker for differentiating T- and B-lymphocytes. For this purpose, we analysed the frequency of AP-positive lymphocytes in the peripheral blood, bone marrow, thymus, lymph node, spleen, and Peyer's patches of normal adult animals 3 months after neonatal thymectomy, and at varying times following administration of intraperitoneal injections of a maximum dose of 16-methylenprednisolone. In normal mice the frequency of AP-positive lymphocytes in peripheral blood and bone marrow corresponds to that of T-lymphocytes in other species. In the thymic cortex, nearly 100% of the lymphocytes show an AP-positive reaction. In the peripheral lymphatic organs these cells are prevailing in the T-dependent areas (paracortex of lymph node, periarteriolar lymph sheet of spleen, and serosa-near region of Peyer's patches). Neonatal thymectomy as well as administration of corticosteroid cause a significant loss of enzyme-positive lymphocytes in the organism. This T-cell reduction becomes particularly evident in B-dependent regions, because in these areas AP-positive (T-) and AP-negative (B-) cells are usually intermingled, and this provides the necessary condition of T/B-interaction, which is of immunological significance. In T-dependent zones, populated mainly by AP-positive cells, neonatal thymectomy results in overall atrophy, while T-cell depletion, expressed as a percentage, is less pronounced within these atrophied areas. Based on these findings the conclusion may be drawn that in Clethrionomys glareolus committed thymocytes, recirculating T-lymphocytes as well as T-helper cells show an AP-positive reaction in contrast to prethymic T-cells, T-suppressor cells and B-cells, which do not express this enzyme. The histochemical demonstration of lymphocytic AP therefore permits an easy visualisation and quantification of T-lymphocytes in Clethrionomys glareolus.