The method for searching for ligands exerting an adjuvant effect is described. The method involves isolation of polysomes using an immobilized peptide mimetic of N-acetylglucosaminyl-N-acetylmuramyl dipeptide (GMDP) - RN-peptide. After the affinity chromatography and washing, RN-peptide complexes with the target sequences were dissociated with guanidine hydrochloride. The obtained mRNA was used for cDNA synthesis and subsequent cloning in an expression vector. Further studies showed the effectiveness of this method. Clones interacting with the peptide were selected using biotinylated RN-peptide. It was found that all clones encode a sequence identical to the protein YB-1. Recombinant antibodies against protein YB-1 were selected from a phage display human scFv library. Using these antibodies, we determined the binding constant of RN-peptide to protein YB-1. Competitive analysis showed that RN-peptide and GMDP compete for the same portion of YB-1 at molar ratio 1 : 12.