High Frequency of CCR5 and CCR2 Expressing T Cells and Its Association with Acute Renal Allograft Rejection

Abstract

Introduction: Acute cellular rejection (ACR) of human renal allografts is a frequent serious post transplantation complication; occurring in up to 50% of renal transplant recipients. Leukocyte recruitment is a central feature of acute allograft rejection. The receptors for chemokines are expressed on leukocytes in a cell type specific manner. Recently it was observed that CCR5+ and CXCR3+ cells were found in allograft biopsies of patients with ACR. Here we investigated the expression of Th1 (CCR5, CXCR3 and CCR2) and Th2 (CCR4, CCR3 and CCR8) associated chemokine receptor on CD4 and CD8 T cell population. Aim: to correlate chemokine receptor expression in peripheral blood T cell subset in patients with ACR (biopsy proven rejections). Methods: Venous blood was collected for fluorescence-activated cell sorter (FACS) analysis at the time of graft rejection (ACR; n=10) (8 men, 2 women; mean age, 29 years; age range, 18-48 years) and well functioning grafts (WFG) (n=21) (20 men, 1 women; mean age, 30 years; age range, 18-48 years) FACS analysis was performed using a FACS calibur flow cytometer and antibodies conjugated with the fluorochromes fluorescein isothiocyanate (FITC), phycoerythrin (PE), Cy5PE as follows: CD4-Cy5PE, CD8- Cy5PE, CXCR3-PE Subsequent gating and analyses were performed using FLOW-JO software. Results: Frequency and expression of chemokine receptors in biopsy proven ACR (n=10) with that of WFG (n=21), frequency of CCR5+ (CD4; 11.08 % vs. 4.37 %; P=0.04), CD8; 27.6% vs. 13.6 %; P=0.02)] and CCR2+ [CD4; 1.23% vs. 0.27%; P=0.0002), CD8; 1.26% vs. 0.22% (P=0.004)] was high in ACR cases. We found high frequency of CCR3 only in the CD8 (0.46% vs. 0.94%; P=0.02) compartment of patients with ACR. Expression of chemokine receptors, analyzed by median fluorescent intensities (MFI), were in coherence with data for chemokine receptor frequency in T cells. MFI of CD4+CCR5+ (270 [202-421] Vs 207 [188-251] P=0.04) and CCR2+ (292[219-577]-161[143-240]) was found to be significantly high in ACR cases in comparison to WFG. Similarly CD8+ CCR5+ (P=0.04)], and CCR2 (193[164-334] vs 169[152-206]) were found to be significantly high in ACR cases. Among Th2 chemokine receptors there was no significant difference in the MFIs of chemokine receptors in ACR and WFG. Conclusion: CCR5 and CCR2 are the major Th1 associated chemokine receptors found to have high expression as well as in frequency during ACR. They seem to play a major role in the T cell mediated renal allograft rejection. However, high CCR3+ CD4 and CD8 T cells ACR (CD8+ only) indicates towards a possible role of this Th2 associated chemokine receptor in balancing the pro and anti-inflammatory T cell function. Thus we propose an important role of both CCR5 and CCR2 in T cell recruitment in the renal allograft during ACR and these receptors are possibly an important point of intervention for development of new therapeutic modalities as well as non interventional prognostic assay for monitoring allograft function.