Morphological differences in the interactions between human mononuclear cells and coated or uncoated sheep red blood cells

Summary Enriched preparations of E, EA and EAC rosettes formed by human peripheral blood mononuclear cells were freeze-etched and examined electron-microscopically. In E rosettes only lymphocytes were involved, whereas in EA and EAC rosettes lymphocytes and mononuclear phagocytes participated as rosette-forming cells. In EA and EAC rosettes, cytoplasmic extensions of the rosette forming cell were seen to penetrate the sheep red blood cell, whereas E rosettes showed a broad zone of adherence without penetration. None of the three types of rosettes showed an interspace between the membranes. Unlike E rosettes, EA and EAC rosettes showed polarity in the adherence of sheep red blood cells. These observations made by freeze-etch electron microscopy indicate distinct morphological differences between rosettes formed with coated or uncoated erythrocytes.The authors wish to thank Prof. Dr. A. Cats, Dr. P.C.J. van Breda Vriesman and Dr. J.C.H. de Man for helpful discussion and criticism; the assistance of Miss R. Kleinjan and Mrs. A.C. Scheurkogel-van Efferen is gratefully acknowledged. This work was supported in part by a grant of the Praeventiefonds