ABSTRACT
The immune adherence receptor on erythrocytes in humans, complement receptor type 1 (CR1) participates in host defense by binding complement opsonized foreign antigens in the circulation and delivering them to the liver and spleen for destruction and immune response. Several CR1 polymorphisms have been described for the type 1 transmembrane glycoprotein whose extracellular portion is composed entirely of complement control proteins. CR1 is expressed by all types of peripheral blood cells except for platelets and most T cells. CR1 on erythrocytes binds immune complexes coated with C3b/C4b. CR1 has been reported to bind C1q and mannan-binding lectin, and this binding could contribute to opsonization of immune complexes. A growing body of data points to CR1’s participation in multiple aspects of the humoral immune response and is consistent with its presence on immunocompetent cells. There are conflicting data on the effect that signaling through CR1 has on B-cell proliferation.
