T H E Proliferative and Anamnestic Antibody Response of Rabbit Lymphoid Cells I N Vitro Ii . Requirement for Adherent and Nonadherent Cells of the Responses to Particulate Antigens in Spleen Cell

Primary and secondary immune responses to sheep erythrocytes have been obtained in tissue cultures of dispersed mouse spleen (1, 2), and such cultures provide a means of investigating, at the cellular level, the in vitro antibody response. The results of Mosier (3) suggest that at least two different cell populations in mouse spleen suspensions are required for the primary response to sheep erythrocytes in vitro, one with propensity for adhering to glass or plastic surfaces, and the other a nonadherent population. I t has been suggested that the "adherent" cells, which have been shown to be non-thymus-dependent (4), insensitive to tolerance induction (5), and resistant to 1000 R X-irradiation (6) are primarily macrophages. These cells can be incubated with the erythrocyte antigen, and then after washing recombined with the nonadherent cell population for production of a primary response. The role of these adherent cells in the secondary response is not established, since it has been reported recently that nonadherent spleen cells from sensitized mice may give a secondary in~nune response to sheep erythrocytes in vitro (7). The present studies were undertaken to examine whether primary and secondary responses could be induced in cultures of dispersed rabbit spleen cells, and to determine whether adherent and nonadherent cells were also required for an immune response in the rabbit spleen cell culture system. Since it was found that an antibody response could be obtained to Brucella abortus antigen as well as to sheep erythrocytes in rabbit spleen cell cultures, it was possible to extend the study of in vitro cell interactions to the immune response to a bacterial antigen. The results shown below indicate that the in vitro immune responses of nor-