1D SDS-PAGE analysis of material captured by a CTLA-4 specific affinity column. CTLA-4 negative plasma (donor 17) and CTLA-4 positive plasma (donor 19) were passed through a column linked to the CTLA-4 specific antibody AS32. Material was eluted at low pH and collected into fractions that were separated by 1D-SDS PAGE. Coomassie blue staining was used to visualize protein patterns. A box marks the single band enriched in donor 19 compared to donor 17.