Regulatory role of the carcinoembryonic antigen (CEA)-family molecules in the innate eosinophil response to staphylococcus aureus

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Rationale The CEA family belongs to the immunoglobulin superfamily and is expressed mainly on mucosal tissue cells and granulocytes. While CEA molecules are highly expressed on eosinophils from patients with helminth infection, the significance of these molecules is unknown. Hence, we investigated in vitro the expression and functions of the CEA family of molecules in eosinophils. Methods We examined the expression of two CEA family molecules, CGM6 (CD66b) and CEA (CD66e), before and after incubation with IL-5 or heat-killed Staphylococcus aureus (Staph) by FACS and laser scanning microscopy. The functions of these molecules in the eosinophils' responses to Staph, such as binding and superoxide production, were examined by ligating them with specific monoclonal antibodies (mAbs). Results Both CGM6 and CEA were constitutively expressed on eosinophils; their expression was upregulated when cells were incubated with IL-5 or Staph. By laser scanning microscopy, CGM6 and CEA were stained on the peripheral surface and on pseudopods of adherent eosinophils, suggesting their roles in adhesion. Incubation of eosinophils with anti-CGM6 or anti-CEA mAb significantly enhanced eosinophil binding to Staph. Furthermore, anti-CEA, but not anti-CGM6 mAb, significantly enhanced superoxide production by eosinophils in response to Staph. In contrast, IL-5-induced superoxide production by eosinophils was not affected by anti-CEA or anti-CGM6 mAb. Conclusions The CEA family of molecules is upregulated in activated eosinophils and is involved in regulating the eosinophil response to Staph. Further studies will address the roles of these molecules in the innate immune response of eosinophils.