Direct binding and lectin-mediated binding of erythrocytes to haemocytes of the insect, Extatosoma tiaratum.

Treatment of Extatosoma haemocytes on a monolayer with fixed rabbit erythrocytes (RE) in the presence of Ca2+ results in ca. 11% plasmatocytes (PL) and 58% spreading granular (SG) cells rosetting. Pretreatment of haemocytes with lactose, D-galactose, or asialofetuin reduces rosetting, suggesting that the membrane-associated receptors involved may be lectins. The percentage of rosetting PL and SG cells is increased by a number of heterologous lectins (indicating the presence of D-galactose, mannose, and Glu Nac receptors on these haemocytes) and a D-galactose specific lectin isolated from the serum of the insect. The latter acts as a bridging molecule and requires Ca2+ to bind to specific receptors on both haemocytes and fixed RE.