CELLS INVOLVED IN T H E IMMUNE RESPONSE VII. THE DEMONSTRATION, USING ALLOTYPIC MARKERS, OF ANTIBODY FOR- MATION BY IRRADIATION-REsISTANT CELLS O1~ IRRADIATED RABBITS INJECTED WITH NORMAL ALLOGENEIC BONE MARROW CELLS AND SHEEP ERYTHROCYTES*

In previous communications, it was demonstrated that normal rabbit bone marrow cells are capable of reacting with antigens in vitro (1-3). After administration of an antigen, the bone marrow cells lose the capacity to react to this particular antigen, whereas their reactivity to other antigens is not impaired. I t was demonstrated (4, S) that spleen cells of irradiated rabbits injected with homologous normal bone marrow cells and immunized with sheep erythrocytes produce many plaques when incubated with sheep erythrocytes and complement in the hemolysis in agar gel technique of Jerne et al. (6, 7). However, if the donor of the bone marrow cells had been injected with sheep erythrocytes 24 hr prior to sacrifice, the bone marrow recipient was unable to mount a successful immune response to the sheep red cells (4, 5). These results suggest the migration from the bone marrow of antigen reactive cells after contact with the antigen. However, the possibility that antibody-formlng cells (potential or actual) may normally reside in the bone marrow and may leave the bone marrow along with the antigen-reactive cells after interaction with antigen in vivo cannot be ruled out. The study presented below was designed to determine whether the antibody-forming cells in the spleen of the bone marrow recipient are of donor or recipient origin.