The pathophysiology of renal allograft rejection: a collective review

Mechanism, pathophysiology, diagnosis, and management of renal transplant rejection

In recent years, there has been a steady progress in basic research (immunogenetics and cellular immunology) that helped us in understanding the mechanisms underlying allograft rejection. Several laboratory tests were developed, and the results were shown to correlate with clinical rejection. However, most of these studies have not found a place in clinical practice because of their nonspecificity, lack of sensitivity, time lag, added expense, and inconvenience. The commonly employed diagnostic tests (i.e., renal transplant ultrasound and 131I hippuran scintigram) are helpful in differentiating rejection from other causes of graft malfunction. The specific renal parenchymal disease, such as acute or chronic rejection or de novo or recurrent glomerular disease, contributing to graft malfunction can only be diagnosed by renal histopathologic study. Because hyperacute and accelerated acute rejections are irreversible and necessitate graft nephrectomy, measures should be taken to prevent this problem. High-dose corticosteroids still remain the mainstay of therapy for acute cellular rejection. In the case of steroid-resistant rejections, treatment with ALG or OKT3 appears promising. As there is no effective therapy for chronic allograft rejection, usual measures of delaying the progression of chronic renal failure should be employed, and patients should be advised to return to maintenance dialysis before they develop uremic symptoms. If current experiments demonstrating selective immunosuppression with monoclonal antibodies are found successful in human trials, one can expect further improvement in the outcome of renal transplantation.

Infections in organ transplant recipients

Since the introduction and widespread performance of transplant surgery in the 1950s and 1960s, infectious complications have been a major cause of morbidity and mortality. The risks of infection are directly related to the potency and duration of immunosuppressive therapies, organ-donor selection, surgical techniques, and postoperative exposures to invasive procedures or treatments. Despite impressive advancements to decrease the risks of infection, between 40% and 80% of renal transplant patients become infected within the first two or three postoperative years. Infections that occur during the first month following transplantation are often caused by common nosocomial pathogens and are secondary to invasive procedures or therapies. Infections that occur between one and six months postsurgery are often caused by opportunistic pathogens. Symptomatic and subclinical cytomegalovirus (CMV) infections are common during this time and may contribute to a further impairment of host defenses. Late infections involve both opportunistic and conventional pathogens; opportunistic infections occur in patients with poor transplant function who require high levels of immunosuppression and conventional infections occur in patients who require little immunosuppression. During the past two decades, there has been a significant decrease in deaths from infectious complications among renal transplant recipients. Further reductions in morbidity and mortality will occur with the development of more specific approaches for immunosuppressive therapy, new strategies to prevent CMV infections and methods to eliminate sources of nosocomial infections.

Fibrosis of a renal transplant ureter

Ureteral obstruction following renal transplantation, although not a common occurrence, is a serious complication because of the single functioning kidney. Obstruction may be caused by ureterovesical stenosis, retroperitoneal fibrosis or adhesions, clot formation, pelvic lymphoceles or kinking of the ureter. A case is presented in which there was progressive partial ureteral obstruction caused by fibrosis and stricture of the transplant ureter, which were probably owing to rejection episodes.

Adenosine-aminohydrolase activity in the erythrocytes, lymphocytes, and plasma of healthy subjects and kidney transplant recipients

Adenosine-aminohydrolase activity in the red blood cells and lymphocytes of transplant patients were assayed by continuous flow analysis. This enzyme, which has been implicated in the ability of lymphocytes to mount an immune response, was evaluated in renal allografted patients immunosuppressed by azothiprine and methylprednisone. Red cell adenosine-aminohydrolase activity was depressed in all patients when compared to nontreated health controls. Adenosine aminohydrolase activity was raised in the lymphocytes of the renal allografted patients. Renal transplant patients' in vitro lymphocyte reactivity to antigens, mitogens, or skin testing to specific antigens, confirmed the depressive effects of immunosuppression observed in vivo. We conclude from these studies that red cell adenosine-aminohydrolase activity may be a more sensitive index of the state of immunoresponsiveness than the corresponding enzyme activity in the lymphocyte.