Interdigitating reticulum cells in human renal grafts.

Seventeen human renal graft biopsies taken 1 h to 50 days after transplantation and 3 human renal non-graft biopsies (2 minimal change and 1 non-tumour portion of angiomyolipoma) were investigated with immunoelectron microscopy in order to identify interdigitating reticulum cells (IDC) or dendritic cells (DC) in renal tissues. The antibodies used consisted of a rabbit polyclonal antibody of antihuman S100 beta protein, mouse monoclonal antibodies of antihuman HLA-DR, anti-CD3, and anti-CD1a. IDC or DC were identified in 11 renal grafts. They were found both in the glomerular and interstitial (peritubular) capillary lumens but not in the interstitium of 1 case: both were present in the interstitial capillary lumens and interstitium of another case, and in the interstitium only of 9 cases. In the remaining 6 grafts and 3 non-grafts they were not detected. These 6 grafts and 3 non-grafts did not show any pathological change except for foot process fusion of the glomerular epithelia in 2 cases of minimal change. These findings suggest that IDC or DC are not normally present in human renal tissues. The presence of the cell in the glomerular and peritubular capillary lumens of a biopsy taken after 1 h and their presence in the interstitial capillary lumens of another graft biopsy, suggest that the IDC or DC in human renal grafts are derived from recipients, not donors, and that they migrate from the circulating blood toward the interstitium.