Antibody-inhibiting activity of bone marrow cells in vitro.

Abstract

Mouse bone marrow and thymus cells have been studied according to their immunological reactivity. The test system involved measurement of the levels of IgM plaque-forming cells following the immunization of spleen cells <i>in vitro</i> in the presence of graded numbers of syngeneic bone marrow and/or thymus cells. All experimental evidence showed the existence of a radiosensitive subpopulation of cells in the bone marrow, capable of inhibiting both the primary and secondary IgM-antibody production irrespective of the dose of antigen used in the system. That this inhibition of antibody production may represent a central control mechanism was indicated by a small change in reactivity of antibody-inhibiting cells derived from the bone marrow of tolerant or normal animals. Furthermore, the inability of supernatants from bone marrow cells, premaintamed <i>in vitro</i> with or without antigen, to suppress the immune response suggested the absence of a released humoral factor responsible for their antibody-inhibiting activity. An enhancement of the immune response with all doses of thymus cells and their inability to overcome the inhibiting activity of bone marrow cells suggested that these immunological events are operating independently of each other.