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Chronic allograft rejection remains the major cause of late renal graft loss. Its pathogenesis is complex, depending on both immunological and nonimmunological factors. An important role in development of chronic rejection is ascribed to an ongoing immunological reaction mainly of the humoral type. C4d complement split product, as a stable fragment of complement degradation activated by antigen-antibody complexes, is considered to be an indicator of humoral activity in allografts. The aim of the present study was to establish a correlation between C4d expression and morphological findings specific for chronic rejection among biopsy specimens from patients with deteriorating graft function versus protocol biopsy specimens versus biopsy specimens of native kidneys with glomerular diseases. C4d deposits in peritubular capillaries and glomeruli were observed in 83% of patients with morphological changes of chronic rejection. No C4d expression was found in the protocol biopsy group. C4d deposits in glomeruli localizations were found in kidneys from patients with glomerulopathies; the pattern of distribution was similar to that for antibodies characteristic for glomerulonephritis. There was a positive correlation between C4d expression and morphological features of chronic rejection. In our opinion, only peritubular capillary localization is specific for a rejection process; glomerular localization is nonspecific and probably secondary to antigen-antibody complex deposition in course of some types of glomerulopathies.

Because it is an important factor affecting renal transplant function, BK infections are significant problem in posttransplant. BK nephropathy develops in 5% of renal allograft recipients, in most cases within the first year after the procedure. The gold standard for BK nephropathy diagnosis is still immunohistochemical staining for large T antigen in graft biopsy specimens. The aim of the present study was to evaluate the incidence of and factors influencing BK nephropathy in our renal allograft population. Among 89 renal or pancreas/kidney allograft recipients, BKV DNA was detected in 1 or more serum samples in 17 patients but BK nephropathy was diagnosed in only 1 case. Plasmacytic tubulitis was an exclusive feature in PCR-positive patients with 2 (20%) cases but no such findings in the PCR-negative group. In 40% of patients in the PCR-positive group at least 1 rejection episode was diagnosed versus 22% in the PCR-negative group. There were no significant differences in both groups according to total ischemia time, immunosuppressive treatments, or mean serum creatinine at 1 year after transplantation.

The major reason for late graft losses is chronic rejection. Recently, a large number of studies have indicated that proteolytic enzymes play an important role as mediators of glomerular injury. The cysteine proteinases cathepsins B and L degrade structural matrix proteins such as type I collagen and laminin. We investigated intraglomerular protease activities in 12 patients after kidney graftectomy because of end-stage renal disease following chronic rejection. A group of 12 patients undergoing nephrectomy because of cancer served as controls using only non-involved parts of the kidney. The activities of cathepsins B and L in homogenates of isolated glomeruli were measured fluorometrically methylcoumarylamide substrates and related to DNA content. In rejected kidney allografts we observed significantly enhanced intraglomerular cathepsin B activity and cathepsin B + L activity.

Recent data indicate that aside from its anti-coagulant action heparin has potent immunobiological activities inhibiting cell trafficking to a site of antigen. In addition, heparin inhibits smooth muscle cell proliferation and decreases the synthesis of the extracellular matrix proteins. As those phenomena are thought to play a major role in the pathogenesis of chronic allograft rejection, we performed a trial evaluating the efficacy of low dose heparin (5 U/kg/day) in 23 recipients of renal allografts with biopsy-proven rejection. In 16 patients (70%) a tendency for improvement was seen which in 57% was statistically significant. Our data suggest that low dose non-anticoagulant heparin may be an efficacious means for treatment of chronic rejection.

The functional outcome after the transplantation of 97 cadaveric kidneys stored up to 25 hours with simple hypothermia was analysed in relation to age of donor, extent of pre-agonal kidney damage, the length of warm, cold and standardised ischaemic times and the presence of multiple renal arteries. Analysis of various factors showed that the most important for function after transplantation were pre-agonal anoxic damage and the ratio of the cold/warm ischaemia time. Based on that observation, a diagram has been proposed which allows calculation of the safe cold storage time after retrieval of the kidney.

ADCC activity in 27 cadaver renal allograft recipients was studied. All the patients were given standard immunosuppressive treatment. Significant positive correlation between high ADCC activity during first 5 days after grafting and accelerated rjection crisis was found. The high positive ADCC test may signalize the possibility of acute accelerated rejection of renal allograft.