Studies on human peripheral monocytes Part I. Scanning electron microscopic observation

In order to observe peripheral monocytes by scanning electron microscopy (SEM), a simple method was developed as described below. Mononuclear cell suspensions prepared by Ficoll-Hypaque gradient centrifugation were fixed in 1% paraformaldehyde and then stained with alpha-naphthyl butyrate which served to specifically identify monocytes. Monocytes were recognized by their red-brown color under a light microscope, and processed for SEM. The monocytes were characterized further in healthy controls and patients with bronchogenic carcinoma using this method. The surface of monocytes from controls was uneven and covered with ruffles and ridges. The monocytes from patients with bronchogenic carcinoma were smaller and had more large ruffles than controls. The changes in the surface of monocytes when treated with some chemoattractants were less obvious in patients with bronchogenic carcinoma than in healthy controls. This method is useful in studying the surface structure of peripheral monocytes and may help in further examining monocyte function.