In this paper we describe the first in vitro response to the liver alloantigen F. The anti-F response serves as a valuable model for autoimmune phenomena since priming appropriate strains of mice (responders) with allogeneic but not syngeneic type F leads to autoantibody production. The in vitro system is based on the proliferation of T cells, from mice primed in vivo with F, when coincubated with splenic adherent cells (SAC) prepulsed with F in vivo. The system displays two important correlates of the in vivo antibody response to F:1.T cells from mice primed with syngeneic F do not proliferate when incubated with SAC prepulsed with syngeneic F and 2. Mice that do not make antibody responses to allo F in vivo (DBA/2) do not show in vitro proliferative responses. These findings indicate that the proliferative assay is a good in vitro model for the F response.