REPLACEMENT OF DENDRITIC CELLS IN THE AIRWAYS OF RAT LUNG ALLOGRAFTS

It is unknown whether dendritic cells are able to migrate normally from the recipient into the allogeneic lung graft. Using monoclonal antibodies to major histocompatibility complex class II antigens (OX6 for both donor and recipient types; HIS19 for recipient type), we studied the replacement of donor dendritic cells by recipient type cells in rat lung allografts that are indefinitely accepted with a short course of cyclosporine early after transplantation. The recipient dendritic cells started to migrate into lung allografts early (by 1 wk) after transplantation. Donor dendritic cells in the grafts were replaced by recipient cells during the first 2 months after transplantation. Dendritic cells in the perivascular tissue were replaced quickly, most of them within 1 wk, whereas those in the alveolar septa were replaced slowly. In the lung allograft surviving 2 or more months, the normal phenotypic heterogeneity of dendritic cells was preserved. Recipient dendritic cells accumulated in dense peribronchial aggregates that remained 6 months. The dendritic aggregates were associated with late airway changes in allografted lungs. The abnormal accumulation of dendritic cells peribronchially might be related to an abnormal mucosal immune response or a chronic rejection process.