Lung allograft rejection in the rat. I. Accelerated rejection caused by graft lymphocytes

To find out to what extent rejection of lungs differs from that of other organs, functional rejection of lung allografts was studied in five combinations of inbred rat strains. Rejection could be monitored accurately by perfusion scintigraphy, and equally well by chest roentgenography. The rejection of lung grafts was found to proceed remarkably fast, when compared with heart grafts, in combinations with strong RT1-incompatibilities. This accelerated rejection pattern could be converted into rejection at a normal pace by pretreatment of the donor with 10 Gy roentgen irradiation one day before transplantation. Donor pretreatment depleted the lung graft's bronchus-associated lymphoid tissue (BALT) of lymphocytes. When grafts were depleted of all other passenger cells as well--by retransplantation from a cyclosporine-treated intermediate host--they showed an even more reduced immunogenicity, probably because of the loss of donor-type dendritic cells. These results indicate that lymphocytes from the BALT of lung grafts are capable of accelerating the rejection response.