Expression of DNAM-1 (CD226) on inflammatory monocytes

• DNAM-1 is strongly expressed on inflammatory monocytes (iMos).
• In contrast, patrolling monocytes do not express DNAM-1.
• Selective expression of DNAM-1 on iMos is conserved between mice and humans.
• DNAM-1 is involved in adhesion of mouse iMos.

DNAM-1 is an activating receptor expressed on NK cells and T cells and plays an important role in cytotoxicity of these cells against target cells. Although the role of DNAM-1 in the function of T cells and NK cells has been well studied, the expression and function of DNAM-1 on myeloid cells have been incompletely understood. In this study, we investigated expression of DNAM-1 on monocyte subsets in mouse peripheral blood and found that only inflammatory monocytes (iMos), but not patrolling monocytes (pMos), expressed high levels of DNAM-1. In addition, we found that DNAM-1 was highly expressed on iMos, rather than pMos, also in human. Furthermore, we found that DNAM-1 on inflammatory monocytes was involved in cell adhesion to CD155-expressing cells. Therefore, we propose that expression of DNAM-1 on inflammatory monocytes are evolutionally conserved and act as an adhesion molecule on blood inflammatory monocytes.