The murine inhibitory receptor mSiglec‐E is expressed broadly on cells of the innate immune system whereas mSiglec‐F is restricted to eosinophils

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Abstract
Murine (m) Siglec‐E and mSiglec‐F are recently discovered murine sialic acid‐binding Ig‐like lectins with tyrosine‐based inhibitory signaling motifs. They are postulated to be the orthologs ofhuman (h) siglec‐7, ‐8 or ‐9 and siglec‐5, respectively. We report here the first detailed characterization of mSiglec‐E, and compare its expression pattern with mSiglec‐F. Similar to hSiglec‐7, mSiglec‐E preferred α2–8‐linked disialic acid over α2–3‐ and α2–6‐linked sialic acids. Using a specific Ab, FACS analysis demonstrated that mSiglec‐E was expressed mainly on neutrophils inblood and their immature precursors in bone marrow. mSiglec‐E was present on peritoneal cavity macrophages and on subsets of mature NK cells and splenic dendritic cells. mSiglec‐E was also found ona novel population of peritoneal cavity B‐1a‐like cells and a subset of splenic B cells enriched in transitional T2 and marginal zone B cells. In striking contrast to mSiglec‐E, mSiglec‐F was expressed predominantly on eosinophils in blood and their precursors in the bone marrow. The distinct and largely non‐overlapping expression profiles of mSiglec‐E and mSiglec‐F suggest that they play non‐redundant roles in the innate immune system. mSiglec‐E is likely to modulate the functions of several types of effector cells, whereas mSiglec‐F is likely to be more restricted to eosinophil biology.