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Increased Concanavalin A-dependent Agglutinability of Mouse Fibroblasts after Treatment with Leukocyte Lysosomal Preparations¹

Department of Pathology, Health Sciences Center, State University of New York, Stony Brook, New York 11790

Brief exposure of cultured 3T3/4 mouse fibroblasts to extracts of human leukocyte lysosomes renders the cells agglutinable by low concentrations of concanavalin A, a plant lectin. Untreated cells are not agglutinated by the same concentration of concanavalin A. Methyl--D-mannoside, a haptenic sugar specific for concanavalin A binding sites, prevents the agglutination reaction of treated cells. At least two fractions of the leukocyte lysosomal extract are active and can be separated by chromatography through Sephadex G-75. One fraction, with strong activity, is heat labile, is ineffective if incubated with cells in the cold, and is suppressed by a polypeptide chloromethyl ketone inhibitor of elastase. It is suggested that an enzyme, possibly the leukocyte elastase previously identified in human granulocytes, may be responsible for the activity of this fraction. Weaker activity is also present in a larger-molecular-weight fraction of the granule extract. This activity is heat stable, is unaffected by incubation with cells in the cold, and is not suppressed by the chloromethyl ketone protease inhibitor. The observation of enhanced agglutination of cultured mouse fibroblasts by concanavalin A following their exposure to leukocyte lysosomal materials in vitro raises the possibility that a similar alteration of cell surfaces occurs in inflamed tissues as a consequence of leukocyte infiltration and degranulation. Since enhanced agglutination of animal cells by plant lectins is often indicative of surface changes associated with loss of cellular growth control, a similar alteration of cell surfaces in vivo by leukocyte lysosomes could partially explain the tumor-promoting effect of inflammatory agents.

¹ This investigation was supported by USPHS Grants HL 14262 and 1-T01-CA05243. Part of this work was presented at the Federation of American Societies for Experimental Biology, Atlantic City, N. J., April 1972.

² USPHS Trainee. Present address: Biophysics Laboratory, University of Wisconsin, Madison, Wis. 53706.

Received 11/27/72. Accepted 2/15/73.