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Introduction: Chronic allograft nephropathy is the major cause of long-term graft failure in human allografted kidney transplantation. In addition to macrophages and T lymphocytes, mast cells have been shown to increase in chronic allograft nephropathy. The present study examined tryptase-positive mast cells and microvessels in the allografted kidney., Materials and Methods: We selected 131 biopsy specimens obtained from 100 allografted, 14 non-grafted renal biopsy specimens and nine nephrectomy specimens due to renal cell carcinomas. Formalin-fixed, paraffin- embedded specimens were immunostained using primary antibodies for mast cell tryptase, mast cell chymase and CD34. The number of the mast cells and microvessels was counted in at least 20 high-power fields (10 x 40)., Results: Tryptase-positive mast cells outnumbered chymase, toluidine blue or naphthol-AS-D choloacetate-positive mast cells. The mean number of the tryptase-positive mast cells was significantly higher in the 36 specimens with chronic allograft nephropathy (5.1 +/- 3.5) among the grafted kidneys with other disease categories (P < 0.001). In the chronic allograft nephropathy, the mean numbers of mast cells was significantly higher in Ci 2 + Ci 3 (n = 20; 6.4 +/- 3.89) than in Ci 1 (n = 16; 3.6 +/- 2.65) (P < 0.01). In the non-grafted kidney, the number of mast cells was highest in the four specimens with diabetic nephropathy. Mast cells and microvessels were analysed in the two representative cases, which subsequently developed chronic allograft nephropathy. Both of the cases showed the highest number of mast cells in chronic allograft nephropathy. In contrast, the mean number of microvessels tended to decrease along with interstitial fibrosis., Conclusions: This study demonstrated clearly a close association between renal interstitial fibrosis and mast cells, which might play an important role in the development of chronic allograft nephropathy.

This study was conducted to examine the validity and accuracy of telepathology for biopsy specimens from allografted kidney. The still video images of paraffin sections were transmitted via a two-way telephone by use of a digitized telephone network, ISDN. The quality of the transmitted images was sufficient for the diagnosis, especially at higher magnification. A total of 37 needle biopsy specimens from the 31 allografted kidneys were presented for consultation and diagnosed by an expert pathologist at Tottori University, until July 2000. The average number of transmitted images was 7.1 (range 3-12). Of the 37 specimens, diagnoses by telepathology agreed well with those made through direct microscopy in the 30 specimens. Insufficient or improper diagnosis was made in four specimens, in which proper and pathognomonic still images were not transmitted. Three cases were not diagnosed by telepathology because of the difficulty in making differential diagnosis. From these results, we concluded that telepathology is useful for transplantation pathology, in spite of limitations in some cases.

To clarify the clinico-pathological significance of protocol biopsy and clinically silent rejection in the management of renal graft recipients, we selected a total of 139 (23%) from 604 biopsy specimens according to the following criteria: 1) less than 1.4 mg/dL of serum creatinine and 2) more than 1,500 mL/d of urine volume at time of biopsy. Clinical indications for the biopsy were classified into five categories: i) protocol biopsy (73 specimens), including 69 cases at discharge post-transplantation; ii) slight increase in serum creatinine (32); iii) proteinuria (20); iv) evaluation of pulse-therapy (13); and v) fever elevation (1). Except for the last category, the specimens were histopathologically diagnosed as being normal in 50 (68%), 6 (17%), 1 (5%), and 5 (38%) specimens, respectively. Even borderline changes, and mild acute rejection, as well as drug-induced nephropathy were included, implying the existence of clinically silent rejection or drug-induced nephropathy. Obvious diversity in the histopathological diagnosis was noted in category iii) showing proteinuria, which was mainly caused by chronic rejection, drug-induced nephropathy and glomerulonephritis. The graft survival rate was no different among the four categories, except for category v). These results indicate that biopsies obtained from functionally sufficient renal grafts could provide useful information in the management of the recipients. The clinical significance of protocol biopsy awaits further clarification by the analysis of a large number of cases.