Human immunity to rat antigens.

A test has been devised with the object of assaying immune responsiveness in normal and immunodepressed persons. It has been based on the graft-versus-host model of Ford et al. (Transplantation 10: 258, 1970) and employs rat antigens as the immunological stimuli. Peripheral blood lymphocytes were injected into the hind feet of young Wistar rats, and 7 days later the popliteal lymph nodes were removed and weighed. It was found that the unwanted host-versus-graft activity could be suppressed in the rats by total body irradiation. Inactivated lymphocytes were injected into the right hind foot as a control and the result was expressed as a ratio: weight of left node to weight of right node. Lymphocytes from 45 healthy individuals were examined in this way. The response was readily suppressed by administering daily injections of steroid or antilymphocyte globulin to the rats, but was not influenced by the presence or absence of antirat antibodies in these individuals.