Physiological evidence of integrin-antibody reactive proteins influencing the innate cellular immune responses of larval Galleria mellonella hemocytes.

Larval Galleria mellonella (L.) hemocytes form microaggregates in response to stimulation by Gram-positive bacteria. Hemocyte adhesion to foreign materials is mediated by the cAMP/ protein kinase A pathway and the β-subunit of cholera toxin using a cAMP-independent mechanism. Cholera toxin-induced microaggregation was inhibited by the integrin inhibitory RGDS peptide, implying integrins may be part of the mechanism. Based on the types of mammalian integrin-antibody reactive proteins affecting hemocyte adhesion and bacterial-induced responses α , α , β , and β subunits occurred on both granular cell and plasmatocyte hemocyte subtypes. A fluorescent band representing the binding of rabbit α -integrin subunit antibodies occurred between adhering heterotypic hemocytes. The frequency of the bands was increased by cholera toxin. The α and β rabbit integrin subunit antibodies inhibited removal of Bacillus subtilis (Cohn) from the hemolymph in vivo. A α β -specific synthetic peptide blocker similarly diminished hemocyte function whereas the α β -specific inhibitory peptide and the corresponding integrin subunit antibodies did not influence nonself hemocyte activities. Western blots revealed several proteins reacting with a given integrin-antibody subtype. Thus integrin-antibody reactive proteins (which may include integrins) with possible α and β epitopes modulate immediate hemocyte function. Confocal microscopy established plasmatocyte adhesion to and rosetting over substrata followed by granular cell microaggregate adhesion to plasmatocytes during early stage nodulation.