Turnover of dendritic cells in rat heart.

Taking advantage of the high class II (I-region-associated) antigen content of the tissue dendritic cells and monoclonal antibodies directed to the backbone determinants of the bone marrow donor strain, we have investigated the location and analysed the turnover rate of tissue dendritic cells in rat heart. Low numbers of class II-expressing, factor VIII-negative, non-phagocytic cells with dendritic appearance were observed between the heart muscle fibres. After irradiation with 960 rad, these cells were no longer visible but they reappeared (in lower numbers) on day 20, indicating that they are relatively radioresistant but the antigen expression is radiosensitive. Transplantation of allogeneic bone marrow demonstrated that similar cells appeared from the transplanted bone marrow on day 10, and that these cells populated the heart at a maximum of 20-25 days after transplantation. This indicates a relatively rapid turnover rate, comparable with the turnover rate of dendritic cells in rat kidney and mouse lymphoid tissue.