The cells involved in cell-mediated and transplantation immunity in the normal outbred rabbit. XIII. The identity of the responder cells and the role of phagocytic cells in the mixed leucocyte culture reaction.

The ability of rabbit spleen cells depleted of thymus, bone marrow or appendix-derived cells to respond in the one-way mixed leucocyte reaction (MLR) has been investigated. The specific subpopulations of lymphoid cells were eliminated by lysis of these cells in the presence of specific antisera and complement. Phagocytic cells (monocytes and heterophils) were removed with a strong magnet after incubation with carbonyl iron particles. The results indicate that the MLR-responding cells are thymus-derived and that neither bone marrow-derived cells nor appendix-derived cells are essential for the blastogenic response following stimulation with allogeneic cells. A minimum number of phagocytic cells is required for a significant response. These cells, however, exhibit a non-specific (accessory) role and can be supplied by either the responding or the stimulating cell population.