Monocyte implication in renal allograft dysfunction

Abstract

Macrophages are involved in the development and progression of kidney fibrosis. The aim of this study was to analyse the phenotype of circulating monocytes and their ability to predict kidney allograft dysfunction in living kidney transplant recipients. Whole blood samples from 25 kidney recipients and 17 donors were collected at five time-points. Monocyte phenotype was analysed by flow cytometry, and interleukin (IL)-10 and soluble CD163 by enzyme-linked immunosorbent assay. One week after transplantation, surface CD163 and IL-10 levels increased significantly from baseline [2·99 ± 1·38 mean fluorescence intensity (MFI) to 5·18 ± 2·42 MFI for CD163; 4·5 ± 1·46 pg/ml to 6·7 ± 2·5 pg/ml for IL-10]. This CD163 increase correlated with 4-month creatinine levels (r = 0·4394, P = 0·04). However, soluble CD163 decreased significantly from baseline at 1 week (797·11 ± 340·45 ng/ml to 576·50 ± 293·60 ng/ml). CD14(+) CD16(-) monocytes increased at 4 months and correlated positively with creatinine levels at 12 and 24 months (r = 0·6348, P = 0·002 and r = 0·467, P = 0·028, respectively) and negatively with Modification of Diet in Renal Disease (MDRD) at 12 months (r = 0·6056, P = 0·003). At 4 months, IL-10 decreased significantly (P = 0·008) and correlated positively with creatinine at 2 years (r = 0·68, P = 0·010) and with CD14(+) CD16(-) monocytes at 4 months (r = 0·732, P = 0·004). At 24 h, levels of human leucocyte antigen D-related declined from 12·12 ± 5·99 to 5·21 ± 3·84 and CD86 expression decreased from 2·76 ± 1·08 to 1·87 ± 0·95. Both markers recovered progressively until 12 months, when they decreased again. These results indicate that monitoring monocytes could be a promising new prognostic tool of graft dysfunction in renal transplant patients.

Keywords: allograft dysfunction; inflammation; monocytes; renal transplantation.

Fig. 1

Flow cytometry analysis of CD163 expression on circulating monocytes at different time-points after renal transplantation. (a) Representative gating strategy of CD14⁺ monocytes and histograms of CD163 expression. The histograms shown were taken from one kidney recipient and one donor. Kinetics of CD163 expression on peripheral blood monocytes from transplant kidney recipients (n = 18) (b, i) and donors (n = 8) (b, ii). Soluble CD163 (b, iii) levels in serum of renal transplant recipients (n = 14) were analysed by enzyme-linked immunosorbent assay (ELISA) at the time-points indicated. (b, iv) A positive correlation was found between the increment of CD163-positive cells at 1 week and creatinine values at 12 months after surgery (n = 22). For statistical significance, we used Wilcoxon's test and Spearman's correlation. *P < 0·05; **P < 0·01; ***P < 0·001. MFI: mean fluorescence intensity; ΔCD163_1week-B: increment of expression of CD163 on monocytes of renal transplant patients at 1 week after surgery; sCD163: soluble CD163.

Fig. 2

Correlation between circulating monocytes and renal function. We determined total counts (a) and percentage (b) of CD14⁺CD16^– monocytes in peripheral blood from transplant recipients (n = 18) and percentage of CD14⁺CD16^– monocytes from living donors (n = 8) (c) at the indicated times. We next correlated creatinine values at 12 (n = 22) (d) and 24 (n = 22) (e) months and Modification of Diet in Renal Disease (MDRD) at 12 months (n = 22) (f) with the increment of CD14⁺CD16^– monocytes at 4 months after renal transplantation. For statistical significance, we used Spearman's correlation. Interleukin (IL)-10 levels in serum of renal transplant recipients (n = 14) were analysed by enzyme-linked immunosorbent assay (ELISA) at the time-points indicated (g). *P < 0·05; **P < 0·01; ***P < 0·001. ΔCD14⁺CD16^–_M4-B: increment of percentage of CD14⁺CD16^– monocytes of renal transplant patients at 4 months after surgery.

Fig. 3

Profile of antigen-presentation and co-stimulation markers on monocytes from renal transplant recipients. Expression of CD86 (a, n = 19 and d, n = 7), human leucocyte antigen D-related (HLA-DR) (b, n = 16 and e, n = 7) and CD80 (c, n = 19 and f, n = 8) markers were analysed by flow cytometry on peripheral blood monocytes in transplant patients and donors at indicated times. Wilcoxon's test was used for statistical significance. *P < 0·05; **P < 0·01; ***P < 0·001. MFI: mean fluorescence intensity.