Primary antibody response of rabbit blood lymphocytes in vitro

This paper describes a method for in vitro induction of a primary response of rabbit peripheral blood lymphocytes to sheep red blood cells. The response is measured by visualizing and enumerating the plaque-forming cells (PFC). Removal of an adhering suppressor cell and use of a low cell concentration in culture are among the crucial requirements. Maximum response was usually reached after 10--15 days of culture. The number of PFC then decreased or stayed at roughly plateau level at least up to the fourth week of culture, when most of the experiments were terminated. In several instances the response had a cyclical character with repeating peaks of PFC. Only plaques of the direct type were found.