Whole blood will be collected into dipotassium ethylenediaminetetraacetic acid (EDTA) tubes resulting in a final EDTA concentration of 4.5 mM. Plasma will be separated from whole blood by centrifugation (10 minutes at 3000 RPM) and frozen at -80 degrees C until further use. Subjects will be genotyped for signal nucleotide polymorphisms for I62V and Y402H using TaqMan single nucleotide polymorphisms (SNP) genotyping assays. Complement pathway protein analysis will be performed by ELISAs.