Fig. 8. Association between CD81 and TfR2 in LDTI membranes and exosomes. (A) 40 µg of exosomes (EXO) and 10 µg of LDTI purified from K562 cav cells were immunoprecipitated with an anti-CD81 mAb, resolved by SDS-PAGE under non-reducing conditions and immunoblotted against TfR2 and CD81. As a control of antibody specificity, non-immune serum (IgG) was used to immunoprecipitate the lysates. (B) Exosomes prepared from K562 cav cell culture medium were incubated with beads coated with anti-TfR2 mAb in the absence of detergents; the purified TfR2⁺ exosomes (IP with TfR2) were then lysed and immunoblotted against TfR2, TfR1 and CD81. (C) K562-derived exosomes were immunoprecipitated with anti-CD81 mAb (IP with CD81) and stained with mAbs for TfR2, TfR1 and CD81. One aliquot of total exosomal lysate (TOT) was loaded as a control.