Expressions and inhibitory functions of CD 300a receptors on purified human basophils

The inhibitory myeloid immunoglobulin receptor CD 300a ( IR p60) has been shown to downregulate mast cell and eosinophil activities, thereby serving as a potential target for inhibiting allergic effector cell input in allergy. Our aims were to study the expression and functional properties of this receptor in purified human basophils, cells that crucially contribute to T h2‐type immunity and allergy. Basophils homogeneously expressed CD 300a as well as the inhibitory receptor CD 200 R on their cell surface, and these expressions increased after anti‐ I g E stimulation. Ig E ‐mediated basophil degranulation was also significantly inhibited by crosslinking of either CD 200R or CD 300a (by 90% and 50%, respectively). Inhibitory SHIP ‐1 phosphorylations were also induced by CD 200 R and CD 300a, although they were not noticeably increased by I g E ‐dependent activation. We conclude that both CD 200 R and CD 300a play a role in reducing I g E ‐mediated basophil function and may crucially govern the known differential activities of these cells in vivo .