[Tannin-mediated attachment of avidin to erythrocytes does not cause their lysis by complement]

It was shown previously that avidin attachment to biotinylated erythrocytes induced their lysis by a homologous complement via an alternative pathway. This phenomenon hindered the use of avidin-coated immuno-erythrocytes as carriers for drug targeting. In the present work it has been demonstrated that avidin attachment to erythrocytes via a cross-linking reagent (tannin) does not induce any lysis by the complement. Tannization provides an attachment of up to 5 x 10(5) avidin molecules per erythrocyte which is commensurate with the value obtained after treatment with biotin esters. However, in contrast with biotinylated avidin-coated erythrocytes tannized cells are not lysed by the complement, while tannization itself does not diminish the erythrocyte sensitivity to lysis by the complement in the presence of activators (hemolytic antibody or activators of the alternative pathway). The avidin-induced lysis by the complement depends on the mode of avidin attachment to erythrocytes. Complement-resistant avidin-coated tannized erythrocytes bind biotinylated immunoglobulins and may therefore be used as carriers for drug targeting. The use of hemolytic antibody in biotinylated immunoglobulins attached to avidin-coated erythrocytes provides their controlled lysis by a complement activated via a classical pathway.