Bone Marrow as Source of Cells in Reactions of Cellular Hypersensitivity

The precise origin of cells infiltrating tuberculin skin reactions was studied with the technique of immunofluorescence. Thymectomized, irradiated Lewis rats were restored with bone marrow from allogeneic or F(1) donors. They were passively sensitized to tuberculin by a subsequent transfer of Lewis lymph node cells and were given intradermal skin tests with tuberculoprotein. In 24 hr reactions the majority of cells were shown to be derived from the infused marrow. These results were the same regardless whether the lymphocyte transfer was performed on the day of irradiation and marrow injection or 7 days later. The cells in the tuberculin reactions, marrow, spleen, and lymph nodes not derived from the bone marrow were found to originate in the transferred lymph node cells. The relative percentages of marrow-derived and lymph node-derived cells in the tuberculin reactions remained the same during the 9-24 hr period following skin test.