Chemokine Receptors CCR1, CCR3, CCR7 and Chemokines CX3CL1 and CCL5 are Significantly Up-Regulated and Very Reliable for Acute Rejection Diagnosis of Kidney Transplants

Background: The allo-immune response following organ transplantation constitutes one of the main determinants concerning both short- and long- term outcomes in renal graft recipients. Chemokines and their receptors play a diversified and important role, either homeostatic or inflammatory and direct different immune-competent cell types to the allograft. While deeply studied in the last two decades, controversy persists as a result of chemokines’ pleiotropic actions. We report our analysis of CCR1, CCR3, CCR7, CCL5 and CX3CL1 expression or synthesis by graft-infiltrating cells in human kidney transplants (KTx). At the same time, we tested their robustness in diagnosing acute rejection. Methods: Fine-needle aspiration biopsies (Fnab) were performed either on days 7 or 14 post-transplantation among stable KTx and on the day of acute rejection (AR) diagnosis. Fnab cytopreparations were studied by the enzymatic avidin-biotin complex staining for CCR1, CCR3, CCR7 and CX3CL1. From another subgroup of cases, Fnab samples were cultured for 48 hours and the supernatants were analysed for CCL5 by ELISA. Results: The group of AR cases showed a significantly up-regulated expression of CCR1, CCR3, CCR7 and CX3CL1 and a significantly higher synthesis of CCL5. The positive predictive values were respectively 92%, 97%, 85%, 76% and 78% and negative predictive values were by the same order, 100%, 73%, 100%, 98% and 83%. Conclusions: Our study permits us to advance that CCR1 and CCR3 play a significant and non-redundant role in acute rejection, and it is the first report of CCR3 association with rejection, probably related to CCL5. The presence inside the graft of significant up-regulation for CCR7 surmises that part of antigen presentation may be performed there without being restricted to secondary lymphoid sites. Our results with CX3CL1 confirm other reports.

Innate Immune Response in Human Kidney Transplantation: IRF3 and IRF7 Together with Interferon-Alpha Are Significantly Up-Regulated in Acute Rejection

Background: Ischemia-reperfusion injury of organ transplantation activates several mediators which may link the innate to the adaptive immune response. Down the cascade of TLRs, we selected to study the expression of Interferon Regulatory Factors (IRF)-3 and -7 inside human Kidney Transplanted (KTx) organs and the synthesis of IFNα, the main growth factor induced by them, in KTx aspiration biopsy cultures. Simultaneously, we tested their robustness in diagnosing Acute Rejection (AR). Methods: Fine-needle aspiration biopsies (F-nab) were performed either on day 7 or 14 post-KTx among stable patients or on the day of AR diagnosis. On Fnab cytopreparations, we studied IRF3 and IRF7 by the enzymatic avidin-biotin complex staining, and in a different group of cases we quantified IFNα by ELISA in 48 hours Fnab culture supernatants. Results: AR group showed a significantly up-regulated expression for IRF3 and IRF7, reaching Positive Predictive Values (PPV) of 0.824 and 0.8, respectively, as well as Negative Predictive Values (NPV) above 0.9 for both;IFNα presented a PPV = 1.0 and a NPV = 0.9. A variation in the results was noticed according to different immunosuppressive therapies. Conclusions: Our findings suggest that IRF3 and IRF7, and IFNα which they promote, may be very important players in the early days post-KTx, linking the innate with an adaptive response and triggering acute rejection. These differences were very clear-cut, lending consistency to our speculation. It would be important to scrutinize for other potential effects derived from these IRFs up-regulation which could be of clinical relevance.