Lectin-mediated attachment and ingestion of yeast cells and erythrocytes by hamster fibroblasts

Abstract

Yeast cell attachment to Concanavalin A (ConA)-coated fibroblasts depends on the degree of saturation of ConA-binding sites on the fibroblast. Under comparable conditions, fresh mouse erythrocytes fail to establish stable contacts with ConA-coated fibroblasts. The interaction of ConA-coated erythrocytes with fibroblasts and of non-coated erythrocytes with wheat germ agglutinin (WGA)-coated fibroblasts is remarkably less efficient than that of yeast cells interacting with ConA-coated fibroblasts. Ingestion of attached cells was not observed in any of the above lectin-mediated cell-cell interactions. Yeast cells coated with ConA show a high extent of attachment to fibroblasts (three-fold that of yeast cell attachment to ConA-coated fibroblasts). The attachment is highly temperature sensitive, being 3 times more at 37 °C than at 14 °C. A significant fraction of attached yeast cells (~46%) is ingested by the fibroblasts during the 60 min incubation at 37 °C. The ingestion exhibits a strong temperature dependence, being nil at 14 °C and amounting to 150 and 600 ingested yeast cells per 100 fibroblasts at 24 °C and 37 °C, respectively. Transmission and scanning electron microscopy of ConA-mediated yeast cell-fibroblast interaction indicates a tighter interaction when the yeast cells are coated with ConA than when the fibroblasts are coated with ConA. Thus spreading of the plasma membrane around the attached yeast cell as well as transduction of attachment to ingestion could be triggered only under conditions of a very extensive multibridge interaction between the two apposing surfaces. Such an interaction is not achieved when the mobility of ConA-receptors within the fibroblast membrane plane is restricted as a result of crosslinking with ConA.