Figure 6. Factor H protected Pf4-Cre⁺-Crry^flox/flox mouse platelets from alternative pathway complement attack.

(A, B) FACS analysis of C3 deposition demonstrating that Pf4-Cre⁺-Crry^flox/flox mouse platelets were resistant to AP complement attack in vitro (A) but they became complement sensitive if fH19/20 was added WT mouse serum to block fH function on the cell surface (B). The degree of complement sensitivity of Pf4-Cre⁺-Crry^flox/flox platelets in the presence of fH19/20 was similar to that of DAF^−/−/Crry^−/−/C3^−/− (TKO) mouse platelets (D). Addition of fH19/20 to the incubation of Pf4-Cre⁻-Crry^flox/flox mouse platelets with WT serum did not make them hyper-sensitive to AP complement attack (C), suggesting that Crry alone was sufficient to protect the platelets from AP complement. Results were representative of at least 3 independent experiments.