Congenitally athymic nude (nu/nu) mice have Thy-1-bearing immunocompetent helper T cells in their peritoneal cavity

Heavily irradiated peritoneal cells (PC) from congenitally athymic nude (nu/nu) mice markedly restored the impaired in vitro antibody response of nu/nu spleen cells to sheep erythrocyte antigens (T-dependent antigen), whereas irradiated spleen or lymph node cells from nu/nu mice had no effect on the response. This activity of the irradiated PC of nu/nu mice was completely abolished by treatment with anti-Thy-1.2 antiserum plus normal guinea pig serum (C') and is, therefore, attributable to a function of matured T cells.