IN SEARCH OF A FUNCTION FOR HEMOLIN, A HEMOLYMPH PROTEIN FROM THE IMMUNOGLOBULIN SUPERFAMILY

Hemolin, a bacteria-induced protein present in hemolymph of Manduca se xta, is a member of an immunoglobulin gene superfamily, Its function i s not yet clear, We have examined the binding characteristics of hemol in to M. sexta hemocytes and to Escherichia coli. Purified hemolin was labeled with fluorescein isothiocyanate or I-125 and used to study bi nding of hemolin to hemocytes and bacteria, Hemolin bound to all hemoc yte cell types, The binding of hemolin to hemocytes appears to be nons pecific, rather than to a specific receptor molecule, Labeled hemolin also binds to E. coli cells, and this binding was inhibited by competi tion with unlabeled hemolin, suggesting that hemolin may bind to a spe cific molecule on the bacterial surface.