Macrophage density in early surveillance biopsies predicts future renal transplant function

Abstract

Inflammation impairs renal allograft survival but is difficult to quantify by eye at low densities. Here we measured leukocyte abundance in early surveillance biopsies by digital image analysis to test for a role of chemokine receptor genotypes and analyze the predictive value of leukocyte subsets to allograft function. In six-week surveillance biopsies, T-cell (CD3), B-cell (CD20), macrophage (CD68), and dendritic cell (CD209) densities were assessed in whole slide scans. Renal cortical CD3, CD20, and CD68 were significantly higher in histologic rejection. The CCR2 V64I genotype was associated with lower CD3 and CD209 densities. Above-median CD68 density was significantly associated with lower combined patient and graft survival with a hazard ratio of 3.5 (95% confidence interval 1.1-11.0). Both CD20 and CD68 densities inversely correlated with estimated glomerular filtration rate (eGFR) four years after transplantation. Additionally, CD68 correlated with eGFR loss. Among histological measurements including a complete Banff classification, only CD68 density was a significant predictor of an eGFR under 30ml/min after four years (odds ratio 7.4, 1.8-31.0) and part of the best eGFR prediction set in a multivariable linear regression analysis of multiple clinical and pathologic parameters. In a second independent cohort, the original CD68 median maintained its discriminative power for survival and eGFR. Thus, digital high-resolution assessment of CD68 leukocyte infiltration significantly improves prognostic value of early renal transplant biopsies.

Early interstitial macrophage infiltration with mild dysfunction is associated with subsequent kidney graft loss

“…This finding is consistent with previous observations emerging from protocol biopsies, 5,6,9,10 in keeping with a possible role of macrophages in promoting the activation and recruitment of myofibroblasts to areas of inflammation and eventually leading to fibrosis 11 and is consistent with a recent paper reporting that the macrophage-to-myofibroblast transition may contribute to interstitial fibrosis in both human and experimental chronic allograft injury. 12 Moreover, macrophage infiltration is also associated with poor long-term eGFR behavior in kidneys from deceased but not from living donors, thus confirming a potential role of early inflammation in the risk of subsequent CKD in KTRs after transplantation, and somewhat explaining the better outcome observed in KTRs receiving kidneys from living donors.…”

“…This finding is consistent with previous observations emerging from protocol biopsies, 5,6,9,10 Protocol kidney biopsies of KTRs showed that interstitial macrophage infiltration in the first post-transplant year was associated with the development of renal graft fibrosis. 6 This finding is in keeping with a possible role of macrophages in promoting the activation and recruitment of myofibroblasts to areas of inflammation and eventually leading to fibrosis 11 and is consistent with a recent paper reporting that the macrophage-to-myofibroblast transition may contribute to interstitial fibrosis in both human and experimental chronic allograft injury.…”

Diagnosis of renal transplant rejection: Banff classification and beyond

“…In particular, this strategy may help us to understand and distinguish the inflammatory and profibrotic phases of inflammation and/or the activity of inflammation. To this end, multiplex immunohistochemistry is likely to be especially useful, as inflammatory cells are mixed in nature and vary throughout the rejection process [62][63][64]. Digital pathology has become increasingly popular in pathology practice, both in clinical biopsy diagnosis and in research.…”

In situ multiplex immunofluorescence analysis of the inflammatory burden in kidney allograft rejection: A new tool to characterize the alloimmune response

“…However, different phenotypic and molecular studies uncovered that the composition of the infiltrate may be significant. For example, the quantity of macrophages may be a predictive factor for kidney allograft loss . Moreover, both CD20 + B lymphocyte and CD68 + macrophage (but not CD3 + T lymphocyte) densities in early surveillance biopsies inversely correlate with estimated glomerular filtration rate 4 years after transplantation .…”

“…For example, the quantity of macrophages may be a predictive factor for kidney allograft loss . Moreover, both CD20 + B lymphocyte and CD68 + macrophage (but not CD3 + T lymphocyte) densities in early surveillance biopsies inversely correlate with estimated glomerular filtration rate 4 years after transplantation . Consequently, the use of a panel of antibodies to determine the in situ immunopathologic component at the time of rejection diagnosis may be relevant.…”