Early up-regulation of macrophages and myofibroblasts - A new marker for development of chronic renal allograft rejection

Background. Increased numbers of macrophages and myofibroblasts are observe d to occur in chronic renal allograft rejection (CR). The aim of this study was to examine the expression of cellular markers for the macrophage and m yofibroblast in early renal transplant biopsy specimens and correlate these findings with allograft outcome. Methods. The first postengraftment biopsy specimens from 53 patients who un derwent renal transplantation between January 1993 and December 1995 were s tudied using immunohistochemistry with antibodies to alpha-smooth muscle ac tin, which identifies myofibroblasts and CD68, a marker for monocytes and m acrophages. Patients were followed until December 1998 (mean follow-up 4.7/-1.2 years). Results. Nine patients had progressed to CR by the time of the study, where as 44 patients continued to have stable renal function. A marked increase i n both macrophages (P=0.02) and myofibroblasts (P=0.04) was noted in the fi rst biopsy specimen obtained after engraftment in the patients who develope d CR compared with those with stable allograft function. There was a positi ve correlation between alpha-smooth muscle actin and collagen expression (P =0.0001). Conclusion. Significant increases in macrophages and myofibroblasts occur i n the first renal biopsy specimen in those patients who later develop CR.