A kinetic study of factor I-mediated modification and release of RBC-bound DNA-anti-DNA immune complexes

A tritiated DNA-anti-DNA complement--containing immune complex probe was used to define the mechanism of factor I-mediated modification and release of erythrocyte CR1-bound immune complex in 10 normal control subjects. Experiments were performed with preformed immune complex, autologous erythrocytes, and autologous serum. Control experiments were performed by using a single donor source of erythrocytes and commercial factor I. The data demonstrate that the modification-release rate was first order with respect to factor I concentration, the mean half-life of red blood cell-bound immune complex was 1.7 +/- 0.7 minutes, and the mean percent of total immune complex present as unbound complexes was 19 +/- 11. These data are consistent with a clearance model in which factor I-mediated modification and release of red blood cell-bound immune complex plays a significant role in immune complex handling.