SPIO NW mediated complement activation in normal human sera from different donors. Nanoparticles were incubated in human sera as described for mouse experiments, washed and the deposition of proteins was detected with dot blot assay. (a) Anti-dextran antibody deposition of SPIO NW in sera of six donors shows that only serum of donor 1 contained a significant amount of anti-dextran antibody as verified by inhibition with free 20 kDa dextran (sample labeled as 1/dex); (b) C1q dot blot shows significant dextran-dependent deposition in donor 1; (c) C3 deposition shows significant level of complement activation in all six serum samples; (d) there was no significant correlation between C1q binding and C3 deposition on SPIO; (e) binding of MASP-2 to SPIO NW in human sera. All data represent a mean + SEM of triplicates and the experiments were repeated at least two times. All six samples were from non-smoking, <35 years old Caucasian male subjects.