Long lived nonadherent rabbit macrophages obtained from spleen cell cultures

During the preparation of rabbit-mouse hybridomas, an unusual degree of cellular proliferation and a high level of rabbit immunoglobulin secretion in culture was noted. The proliferation seemed to be dependent on the use of relatively high levels (10%) of fetal bovine serum because it was not seen when spleen cells were cultured using either horse serum or autologous serum in a variety of media. The peak of the proliferative response occurs at 7 to 10 d in culture, after which the lymphoblast population dies rapidly, leaving a large, granular, nonadherent cell as the predominant component in the culture. These cells did not seem to divide further but persisted in very gradually diminishing numbers for many months. This long lived cell has been characterized as a nonadherent macrophage by its morphology, intense esterase staining, expression of an Fc receptor for rabbit IgG, phagocytosis of latex particles and opsonized sheep erythrocytes, and mediation of antibody dependent cell mediated cytotoxicity on chicken erythrocytes.