Background: Duffy antigen/chemokine receptor (DARC) is a non-signaling receptor for multiple chemokines. The role of DARC on red blood cells (RBCs) has remained elusive. The purpose of this study was to analyze selective storage of DARC-binding chemokines in RBCs.
Methods: Peripheral blood from healthy volunteers with DARC-positive blood type was collected in EDTA tubes. The concentration of DARC binding chemokines (i.e., MCP-1, RANTES, eotaxin-1, TARC, and IL-8), DARC nonbinding chemokines (i.e., MIP-1α, IP-10), and several cytokines in the supernatant of purified RBCs before and after hemolysis was measured using Bio-Plex and ELISA assays. Storage of chemokines in RBCs and the expression of DARC were evaluated using flow-cytometry.
Results: The levels of all DARC-binding chemokines except TARC and IL-8 increased significantly after hemolysis. There was no significant increase in any of the DARC non-binding chemokines or in the other cytokines after hemolysis. RANTES, eotaxin-1, and MCP-1 were detectable intracellularly but not on the RBC surface. RANTES was absorbed by RBCs. DARC was expressed intracellularly in RBCs as well as on the surface.
Conclusions: These data suggested that DARC-positive RBCs store RANTES, MCP-1 and eotaxin-1. DARC on RBC may be internalized from the surface in the process of chemokine absorption.