Natural clusterings of Fc receptors on human neutrophils--not affected by the cytoskeletal reagents.

By using sucrose density gradient ultracentrifugation and immunodiffusion, we confirmed the monovalency of the electron microscopic ligand for the receptor for the Fc portion of IgG (FcR) on human neutrophils, which was composed of one ferritin (Fer) molecule and one IgG anti-Fer molecule. Pre-treatment of neutrophils at 37 degrees for 30 min with cytochalasin B, colchicine, both of the reagents, concanavalin A, and tetracaine did not alter the clustering of FcR on the surface, which was demonstrated by the ligand at 0 degrees. The effectiveness of these employed cytoskeletal reagents was determined ultrastructurally by observing the changes of morphology and cytoskeletal structures of treated neutrophils; a novel and unique cellular change of cytochalasin B-treated neutrophils was described which we called arachnocytosis. Under our experimental conditions the cytoplasmic surface of the membrane under the receptor patches did not show any specialized density resembling coated membrane regions. These data verify our previous finding that FeR is naturally clustered on human neutrophils, and suggest strongly that the FcR natural clustering is not primarily mediated by the cytoskeletons consisting of microfilaments (actin) and microtubules, and the coated membrane region. The exact mechanism for FcR clustering on human neutrophils is not clear and remains to be elucidated.