Protein A binds blood-derived molecules that contain CTLA-4 epitopes, but does not interact with recombinant sCTLA-4. Recombinant CTLA-4 (A) and plasma from CTLA-4 ELISA positive donors 19 (B), 22 (C) and 44 (D) were passed over protein A columns. Pre-protein A (Pre), protein A flow through (FT), washes (W1 and W2), and fractions eluted at low pH (E1, E2, E3, and E4) were analyzed by ELISA. Black bars represent BNI3 (coat)/AS33B (capture), grey bars represent AS32 (coat)/AS33B (capture), and white bars anti-MOPC (coat)/AS33B (capture).
Tector et al. BMC Immunology 2009 10:51 doi:10.1186/1471-2172-10-51