Tannin-mediated attachment of avidin provides complement-resistant immunoerythrocytes that can be lysed in the presence of activator of complement.

It was shown previously that avidin attachment to biotinylated erythrocytes induces their lysis by homologous complement via the alternative pathway. This phenomenon hinders the use of avidin-coated immunoerythrocytes as carriers for drug targeting. In the present work we demonstrated that attachment of avidin to erythrocytes via the cross-linking agent tannin does not induce their lysis by complement. Tannization allows attachment of about 5 x 10(5) molecules of avidin per erythrocyte, which is comparable to the value obtained after treatment with biotin esters. In contrast to biotinylated avidin-coated erythrocytes, tannized avidin-coated erythrocytes were not lysed by complement. Tannization itself does not reduce the erythrocyte sensitivity to lysis by complement in the presence of activators of the complement (hemolytic antibody or activators of the alternative pathway). Therefore, the avidin-induced lysis by complement depends on the mode of avidin attachment to erythrocyte. Complement-resistant tannized erythrocytes coated with avidin bind biotinylated immunoglobulins (to 7 x 10(4) molecules per cell), suggesting that tannization might be used for the preparation of complement-resistant immunoerythrocytes.