CD300a is a 60 kDa glycoprotein member of the immunoglobulin superfamily. In human, LMIR1 is expressed on peripheral blood eosinophils, mast cells, neutrophils, plasmacytoid dendritic cells, and various T cell subsets. Antibody cross‑linking of CD300a induces phosphorylation of tyrosine residues in the cytoplasmic domain. This leads to the recruitment of phosphatases SHIP, SHP-1, and SHP-2 and inhibition of NK cell, eosinophil, and mast cell activation. Cross‑linking of CD300a to other surface proteins such as SCF R or Fc epsilon RI on mast cells, Fc gamma RIIA on neutrophils, or CCR3 on mast cells and eosinophils inhibits downstream signaling from those receptors. CD300a cross‑linking also limits the in vivo activities of these cells with a subsequent reduction of allergic inflammation symptoms.