Thymus dependence of theta-bearing cells in the peripheral lymphoid tissues of mice.

In mice thymectomized as newborns, thymectomized as adults and irradiated, and in nude mice with congenital absence of the thymus, there is a marked reduction in the number of θ-bearing lymphocytes in the lymph nodes and spleen. This suggests that θ is present on those lymphocytes which are thymus-derived. Using 51Cr and dye exclusion cytotoxic testing, approximately 65–85 per cent of lymph node and thoracic duct lymphocytes and 30–50 per cent of spleen lymphocytes were found to have θ on their surface.