The designed HVEM(23–39) peptide was synthesized and an affinity test was performed using microcolumn with the immobilized BTLA protein. Three fractions were analyzed: supernatant, last wash and elution by using mass spectrometry techniques. In the supernatant fraction the signal m/z corresponding to the excess of the HVEM(23–39) peptide was observed (Fig 2A). In the last wash fraction, no signal was observed confirming that the excess of peptide was removed (Fig 2B). The presence of m/z signal in elution fraction indicated that the complex between BTLA and HVEM(23–39) was formed (Fig 2C).