ANTI-RO FINE SPECIFICITY DEFINED BY MULTIPLE ANTIGENIC PEPTIDES IDENTIFIES COMPONENTS OF TERTIARY EPITOPES

Anti-Ro (or SSA) is a clinically important autoantibody that is found in 25-40% of patients with systemic lupus erythematosus as well as an even greater proportion of patients with Sjogren's syndrome or subacut e cutaneous lupus. We have studied the binding of anti-Re sera to mult iple antigenic peptides constructed from the sequence of the 60-kD Ro molecule. The results demonstrate that sera bind these peptides in sol id-phase assay. Surprisingly, some of these peptides also form a preci pitin line in double immunodiffusion with anti-Re sera. Formation of l ines of identity in double immunodiffusion as well as absorption studi es indicate that peptides distant in the primary amino acid sequence a nd without shared sequence are bound by the same antibody. In addition , data from surface plasmon resonance demonstrate that peptides identi fied in this manner have protein-protein interactions. Thus, these tec hniques may identify the components of conformational epitopes.