Then those analogs were tested in affinity test. We observed that peptides, which could inhibit the BTLA/HVEM interactions in ELISA tests (Fig 5), were also bound by BTLA protein immobilized in microcolumn (Table 1). The exception was cyclic peptide HVEM(23–39) (C29-C37) which interacted with BTLA in affinity test but in ELISA test its inhibitory effect was not observed. The results suggest that the binding site of cyclic peptides and HVEM(23–39) on the BTLA surface is different.