Increased expression of the high-affinity receptor for IgG (FcRI, CD64) on neutrophils in multiple myeloma.

The surface expression of effector cell molecules on neutrophils was examined in 19 patients with multiple myeloma (MM), 6 patients with monoclonal gammopathy of undetermined significance (MGUS) and 22 healthy control subjects. The expression of Fc receptors for IgG (FcR), complement receptors (CR), and cellular adhesion molecules on neutrophils was determined by flow cytometry and monoclonal antibodies. MM neutrophils exhibited higher expression of FcRI, CR3, and CR4 and lower expression of FcRII and L-selectin than that in MGUS and controls. Granulocyte colony-stimulating factor (G-CSF, 50 micrograms/m2/d) was administered subcutaneously to 8 patients with MM and to 4 healthy volunteers. G-CSF administration increased the expression of FcRI, FcRII, and CR1 on neutrophils and decreased the expression of FcRIII on neutrophils in both groups. The application of G-CSF also resulted in increase of CR3 and CR4 expression and in decrease of L-selectin expression on neutrophils in healthy volunteers but not in MM patients. These findings suggest that MM neutrophils may be activate in vivo and that effector cell molecular expression on MM neutrophils is further modulated by G-CSF application.