Human IgG in immune complexes bound to human erythrocyte CR1 is recognized differently than human IgG bound to an erythrocyte surface antigen.

We have developed several methods, including a new use of magnetic cell separation techniques, to examine how human IgG bound to human erythrocytes can be recognized. We find that human IgG in complement-opsonized immune complexes bound to erythrocyte CR1 is less accessible to several probes than human IgG bound to the rhesus antigen on erythrocytes. These findings suggest that the mechanism by which immune complexes are removed and cleared from erythrocyte CR1 in the circulation is different from the mechanisms which lead to splenic clearance of IgG sensitized erythrocytes.