Distribution of different cell types in the lymphoid organs of the mouse, as determined with sera against thymus and Peyer's patches.

Anti-thymus serum (ATS) absorbed with Peyer's patch cells and anti-Peyer's patch serum (APS) absorbed with thymus cells were prepared. ATS treatment of mice resulted in a suppression of the immune response, measured with as an antigen. APS did not have this effect. ATS and APS were used in the indirect fluorescence test to detect T and B cells. The cells staining with APS were called B cells to indicate that APS might only detect a special fraction of B cells (mature B cells). In Peyer's patches 66 per cent of the cells reacted with APS (B cells), whereas only 19 per cent cells reacted with ATS (T cells). The percentage of T cells in the lymph nodes was high (73 per cent), whereas only 14 per cent B cells were found in this organ. In the spleen almost equal numbers of B and T lymphocytes (32 per cent and 33 per cent) were detected. However, 35 per cent of the lymphocytes were non-reactive with either anti-serum. Bone marrow contained only small numbers of reactive cells (1 per cent T and 2 per cent B cells). Treatment of mice with dimethylbenzanthracene (DMBA) caused an increase in the number of non-reactive cells in Peyer's patches and a dramatic decrease in the number of B cells. The relative increase of the number of T cells in spleen and lymph nodes was not found in Peyer's patches. Cortisone acetate seems also to act primarily on B cells, especially on those of Peyer's patches. In this case also an increase in the proportion of T cells in the spleen was detected.