Insect hemocyte adhesion in vitro: Inhibition by apoliphorin I and an artificial substrate

The major insect lipoprotein, lipophorin, was previously shown to inhibit the in vitro adhesion of cockroach hemocytes. In the present study, we show that the large lipophorin subunit, apoLp-I, is the primary component that prevents adhesion of larval hemocytes of the greater wax moth, and that this inhibition is strongly Ca2+-dependent. We also provide immunological evidence for the existence of the small lipophorin subunit, apoLp-III, in the wax moth, and show that recombinant apoLp-III does not modulate cell adhesion. Finally, we report on the use of an artificial substrate, poly(2-hydroxyethyl methacrylate) as an adhesion inhibitor. Hemocytes do not adhere to the artificial substrate in either normal or Ca2+-free saline, and remain both viable and adherent after exposure. Our results therefore favour the use of this artificial substrate in physiological studies requiring nonadherent hemocyte populations in media containing Ca2+.