Heterogeneity of HLA-DR+ cells in normal human kidney. Immunohistological and cytochemical characterisation of discrete cell populations

Pretreatment of kidney allografts with monoclonal antibodies to CD45: results of a multicentre study. CD45 Study Group

The perfusion of human renal allografts with CD45-specific monoclonal antibodies (mAbs) may reduce their immunogenicity and the incidence of rejection. We performed a safety study in 40 patients receiving their first cadaveric renal transplant. Two milligrams each of the rat CD45 specific mAbs YTH 24.5 and YTH 54.12 were perfused into the grafts prior to transplantation. The patients were followed for 3 months. No patient died, and four grafts were lost, three to vascular causes not considered to be related to antibody perfusion and one to severe rejection. Two patients developed an anti-rat antibody response. Immunohistological double-labelling performed on cortical biopsies taken post-perfusion and prior to wound closure showed that at least 60% of the CD45+ cells were coated by perfused anti-CD45 ('antibody uptake'). Among the patients studied for uptake and episodes of rejection, the incidence of rejection was 75% in 12 patients whose antibody uptake was < 95% compared with 22% in 18 patients with antibody uptake > or = 95% (P = 0.01). We conclude that this treatment was free of adverse effects and that there is a correlation between the uptake of antibody by passenger leucocytes and reduction in acute rejection episodes.

Immunohistochemical study of actin binding protein (p55) in the human kidney

BACKGROUND

In clinical transplantation, "passenger" dendritic cells (DCs) in the allograft have been thought to induce allograft rejection. However, the presence of DCs in the normal human kidney is controversial. Most reports have relied on the examination of MHC class I and II antigen expression in combination with DC morphology for identification of DCs.

METHODS

The distribution of the p55 antigen (fascin), which is selectively expressed by human blood and lymphoid DCs, was investigated by immunohistochemistry.

RESULTS

Our study demonstrates that p55-positive DCs are absent from the normal human kidney and CD1a- and S100-positive cells are absent or very rare. Furthermore, HLA-DR and factor VIII-related antigen show almost complete colocalization in capillaries. In contrast, all 16 kidney biopsies from patients with inflammatory processes demonstrated p55-positive DCs in the cellular infiltrates.

CONCLUSIONS

These results suggest that DCs are not present or are very rare in normal renal tissues but may migrate into the renal interstitium with inflammatory changes.

Pretreatment of renal transplants with anti-CD45 antibodies: optimization of perfusion technique

Pig kidneys were perfused ex vivo with a monoclonal anti-pig CD45 antibody to determine optimum conditions for human kidney anti-CD45 perfusion, as such pretreatment may prolong renal allograft survival. Efficacy of perfused antibody uptake was assessed by immunohistochemical double-labelling of multiple renal biopsies. Antibody uptake by CD45+ cells was rapid, and maximal within one hour of perfusion. An antibody concentration of 40 micrograms/ml more effectively saturated available CD45 binding sites than lower concentrations. Whilst cortical perfusion was homogeneous (median uptake > 99%, minimum 90.0%) after 25, 50 or 100 ml perfusion with 40 micrograms/ml monoclonal antibody (mAb), the medulla was less evenly perfused with 25 ml (median uptake 82.6%) than with 50 or 100 ml (median uptake 98.5% and 98.7%, respectively). Prolongation of renal cold ischaemia of up to 46 hours prior to mAb perfusion did not adversely affect antibody binding. Clamping of the renal vein during and after mAb perfusion was associated with better cortical and medullary mAb uptake than if the vein was left unclamped. These data show that the vast majority of the kidney's CD45+ antigen-presenting cells can be bound by anti-CD45 mAb perfused ex vivo, if an adequate volume and concentration of mAb perfusate is employed and the renal vein is clamped during and after the process.

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.

The origin of Ia antigen-expressing cells in the rat kidney

The lineage of Ia antigen expressing (Ia+) cells that have been detected in the parenchyma and interstitium of the rat kidney has not been defined. The authors have studied the origins of Ia+ cells in chimeric rats using monoclonal antibodies to define cells of bone marrow and parenchymal origin. PVGc RTI rats (recipients) received intravenously 2 X 10(6) bone marrow cells from F1 hybrid PVG RTIc/RTIu rats (donors) 1 day after 1000 rads whole body irradiation. Ia chimerism was monitored in blood and isolated glomeruli by immunofluorescence and in frozen sections by immunoperoxidase, using monoclonal antibodies MRC OX3 (anti-Ia RTIu), MRC OX4 (anti-RTIc and u), and MRC OXI (anti-rat leukocyte common antigen). In normal F1 hybrid kidneys, glomerular cell counts were as follows: OXI+, 7.19 +/- 0.23/gl; OX4+, 3.03 +/- 0.14; OX3+, 2.34 +/- 0.1 (76% detectable expression of RTIu). OXI+, OX4+, and OX3+ cells were codistributed in cells in the interstitium between renal tubules. Proximal tubules were weakly OX4+, OX3+. In chimeric rats 5 days after irradiation, blood leukocytes, and renal OX1+ and OX4+ cells were depleted; OX3+ cells were not detected; by 4 weeks blood leukocytes were restored to normal numbers, and 85% of Ia+ cells were OX3+. By 6 weeks OXI+ and OX4+ cells were restored in glomeruli and interstitium, with increasing expression of OX3+ cells; at 10 weeks 75% of glomerular Ia+ cells were OX3+ (equivalent to detectable level of OX3+ cells in normal F1 hybrids) and OX1+, OX4+, and OX3+ cells appeared in equivalent numbers in the interstitium. Groups of proximal tubules were OX4+ and OX3-. These results in established bone marrow chimeras show that in the normal rat kidney bone marrow derived leukocytes expressing Ia antigen are present in the glomerulus and interstitium. Ia antigen is also expressed on some proximal tubular cells. There is no evidence for endothelial Ia positivity.

Monocyte/macrophage derived cells in normal and transplanted human kidneys

The existence of HLA-DR/Ia-like antigen (Ia)-bearing cells of the mononuclear phagocyte system, macrophages (Mac), and/or interdigitating cells (IDC), in the normal kidney is controversial. If present, such cells may be important in renal transplant rejection. We performed enzyme histochemistry using alpha-naphthyl acetate/butyrate esterases (alpha NAE, alpha NBE), 5'-nucleotidase (5'N), acid phosphatase (AcP), alkaline phosphatase (AlkP), and ATPase (ATP) as well as immunoperoxidase staining for Ia and lectin binding (Ulex europaeus I; UEA) on plastic-embedded tissue sections of normal kidneys and rejected renal allografts. Plastic embedding provides clear visualization of histologic detail and allows specific identification of immunoperoxidase-stained cells. Mac and IDC (shown to be Ia+, alpha NAE+, AcP+, ATP+ in other sites) could not be demonstrated in normal renal interstitium. IDC and Mac were not generally identified in normal mesangium, although they could not be altogether distinguished from Ia+ endothelial cells. Focal mesangial staining for alpha NAE but not alpha NBE was present. Rejected kidneys showed increased numbers of alpha NAE+ cells in glomeruli. These cells were frequently Ia negative and often appeared to be blood monocytes present in capillary lumens. Peritubular capillaries and glomerular endothelium stained strongly for UEA, 5'N, and Ia. Our results suggest that previous reports of the presence of IDC in renal tissue on the basis of staining for Ia on frozen tissue may be due to staining of compressed or obliquely sectioned vascular structures that were not adequately visualized.