Abstract
Normal bone marrow antigen-reactive cells could be stimulated to commence the sequence of intracellular reactions characteristic of the afferent limb of the immune response by incubation with antigen in vitro in cell culture. Injection of these in vitro-stimulated bone marrow cells, along with antigen, into irradiated immunoincompetent recipients resulted in a reconstitution of the host's immune competence that was characterized by plaque-forming capacity in the spleen cells 7 days later. Recipients of cells irradiated following in vitro incubation with the antigen gave normal immune responses, whereas irradiation of the cells before in vitro incubation with the antigen completely suppressed the capacity of these cells to transfer immunocompetence. Bone marrow cells irradiated in vitro could exclude the trypan blue dye but failed to undergo blastogenesis and mitosis when cultured in the presence of phytohemagglutinin.
Data in support of the clonal selection theory, with respect to the antigen reactive cells (ARC) present in the normal rabbit bone marrow, were also presented. Precommitment of the ARC to one antigen could not be subverted even if the cells were incubated for 24 hr in vitro in the presence of a second non-cross-reacting antigen in high concentration. Therefore, the ARC is unipotential with respect to antigenic specificity.
Footnotes
This investigation was supported by a grant (to M. R.) from the Medical Research Council, Canada.
