Purified alkylated C9 (50 ng) was subjected to SDS-PAGE thrice, and blotted onto PVDF membranes (membrane 1, 2, and 3). Each membrane was cut into strips corresponding to the electrophoresed lanes and reacted with individual patient serum samples. As a positive control, serum no. 15 was included on a strip from each membrane. In the figure, the cut strips that were subjected to western blotting are arranged and shown in the order of loading on the original membrane. The lines separating the lanes were not generated by image processing, but are artifacts of the experimental procedure used to separate parts of the membrane for reaction with different serums. Anti-C9 antibody was detected in two of 13 SN-APS patients without known thrombophilia, one of 13 SN-APS patients with thrombophilia, and none of the four control samples.