The CC chemokine receptor 3 CCR3 is functionally expressed on eosinophils but not on neutrophils.

The chemokine subclasses differ in their biological activity to stimulate different kinds of effector cells via distinct chemokine receptors. Controversial results about the expression of the CC chemokine receptor CCR3 on the surface of human neutrophils have been described. To find out whether eosinophil contamination might be responsible for these diverse observations, CCR3 expression on highly purified neutrophils and eosinophils was investigated. We enriched neutrophils from a heterogeneous granulocyte population with immunomagnetic beads coated with various anti-CD52 monoclonal antibodies. This procedure was suitable to enrich neutrophils with a purity of up to 99.85%. Reverse transcriptase-PCR revealed that CCR3 mRNA was not expressed by CD52-negative selected neutrophils. In contrast to these cells, CCR3 mRNA could be detected in a heterogeneous granulocyte population and CD16-negative selected eosinophils. In addition, spectrofluorometric measurement of intracellular calcium concentration ([Ca2+]i) demonstrated that CD52-negative selected neutrophils did not show a transient [Ca2+]i increase following stimulation with the CCR3 ligand eotaxin, whereas the heterogeneous granulocyte population as well as eosinophils did respond. Therefore, previous studies demonstrating the expression of CCR3 on human neutrophils have to be re-evaluated because CCR3 mRNA detection on human neutrophils due to contamination by mRNA from eosinophils could not be excluded.