The function of human NK cells is enhanced by β‐glucan, a ligand of CR3 (CD11b/CD18)

Cells responsible for the natural killer (NK) effect in the human blood can be collected in the low‐density lymphocyte subset and the majority of them express CR3. In addition to the iC3b binding site the CR3 molecules possess an epitope which binds β‐glucan. Ligands of this site can deliver activation signals to CR3‐carrying monocytes and neutrophils. We found that the function of NK cells was also potentiated by preincubation with β‐glucan. The treatment increased the proportion of target‐binding lymphocytes and of the damaged target cells in the conjugates. The monoclonal antibody OKM‐1, directed to the β‐glucan‐binding site of CR3, abrogated this effect. Another CR3‐reactive monoclonal antibody, M522, known to activate monocytes and neutrophils, enhanced the NK function.