Abstract: Glycoprotein I(β₂-GPI) has been identified as a cofactor in the recognition of phospholipid Ag cardiolipin (CL) by anticardiolipin Ab(aCL) purified from patients' serum with autoimmune disease. However, there is a considerable controversy as to the anti-β₂-GPI antibodies occurred in aCL. In order to select β₂-GPI recognizing molecules, β₂-GPIwas used as a probe to screen affinity phage clones panned from a phage peptide library. After four cycles of selection, the phage recovery increased from 2.4×10^-5 % to 1.1×10^-3 %, indicating that a specific enrichment had been achieved. In order to characterize these phage clones, we investigated their specific binding to β₂-GPI and their inhibition of β₂-GPIbinding to antiβ₂-GPIantibodies. Almost 40 percent of clones reflected considerable binding abilities and inhibitory activities towards antiβ₂-GPIantibodies. Agroup of related peptides were identified by DNAsequencing, in which there were seven related peptide sequences, with four of them representing more than once. These peptide sequences display similarities at several positions. Sequence motif (—F—S—L—) was evident in most of the peptides. It suggests that these peptides may specifically block the anti-β₂-GPI antibodies binding to β₂-GPI. Our result supports the idea that β₂-GPI acts as a Ag for these anti-β₂-GPI antibodies occurred in the aCL.

Key words: β₂-Glycoprotein, Phospholipid, Anticardiolipin Ab, Phage