CR1 and diabetic retinopathy: The soluble forms of CD35, CD46, CD55, and CD59 are released from the blood cells, primarily leukocytes, via different processes including cell damage and activation, cleavage by matrix metalloproteinases (MMPs), enzymatic cleavage via phospholipase C and/or D, and have been implicated in several chronic inflammatory diseases including SLE, Chagas disease, and diabetic retinopathy (12–14, 23).