HVEM (14-39) is a B- and T-lymphocyte attenuator ( BTLA ) peptide inhibitor. HVEM (14-39) can be combined with BTLA with a K D of 0.102 μM. HVEM (14-39) enhances the activation and proliferation of T cells by regulating the expression of BTLA and HVEM in T cells, and promotes the transformation of cells into effector memory T cells. HVEM (14-39) inhibits tumor cell proliferation and promotes late apoptosis. HVEM (14-39) has immunomodulatory effects and can be used in the study of cancer.