Chemokine receptor usage by human eosinophils. The importance of CCR3 demonstrated using an antagonistic monoclonal antibody.

TLDR

Chemokines signal through G‑protein coupled receptors, and leukocyte subsets such as eosinophils express CCR3, enabling selective homing to inflammatory sites via multiple CC chemokines. The study aimed to develop and characterize the monoclonal antibody 7B11 as a selective CCR3 antagonist. 7B11 was shown to block radiolabeled chemokine binding to CCR3 transfectants and eosinophils, and to inhibit CCR3‑mediated chemotaxis and calcium flux, even in IL‑5‑primed cells that upregulate CXCR2. Blocking CCR3 with 7B11 reduced >95 % of eosinophil responses to eotaxin, RANTES, MCP‑2, MCP‑3, and MCP‑4, confirming CCR3’s central role and demonstrating that complete receptor antagonism is achievable.

Abstract

Chemokines bind and signal through G-protein coupled seven transmembrane receptors. Various chemokine receptors are expressed on leukocytes, and these may impart selective homing of leukocyte subsets to sites of inflammation. Human eosinophils express the eotaxin receptor, CCR3, but respond to a variety of CC chemokines apart from eotaxin, including RANTES, monocyte chemotactic protein (MCP)-2, MCP-3, and MCP-4. Here we describe a mAb, 7B11, that is selective for CCR3 and has the properties of a true receptor antagonist. 7B11 blocked binding of various radiolabeled chemokines to either CCR3 transfectants, or eosinophils. Pretreatment of eosinophils with this mAb blocked chemotaxis and calcium flux induced by all CCR3 ligands. In all individuals examined, including allergic and eosinophilic donors, > 95% of the response of eosinophils to eotaxin, RANTES, MCP-2, MCP-3, and MCP-4 was shown to be mediated through CCR3. The IL-8 receptors, particularly CXCR2, were induced on IL-5 primed eosinophils, however these eosinophils responded to CC chemokines in the same manner as unprimed eosinophils. These results demonstrate the importance of CCR3 for eosinophil responses, and the feasibility of completely antagonizing this receptor.