in vitro complementation experiments with nude mice. i. the allogeneic effect in the antibody response to sheep red cells

Complementation experiments were carried out in which allogeneic spleen cells were added to the spleen cells from nude mice. Evidence is presented that anti‐Θ sensitive T cells are responsible for the complementation. Experiments are described in which the anti‐sheep red cell response is followed as a function of the number of allogeneic spleen cells used to supplement the nude spleen cell cultures. With increasing numbers of allogeneic cells, optimum complementation is observed and then, a rapid drop of the response as the number of allogeneic cells is increased further. As few as 20 x 103 allogeneic spleen cells are able to complement 20 x 106 nude spleen cells to give a significant response. A delay in the addition of allogeneic cells up to 24 h does not change the kinetics of the response.