The decrease of lymphocyte interferon gamma expression during aging is one of the main mechanisms leading to the immunodeficiency state in the elderly. Cell penetrating geroprotective peptide Ala-Glu-Asp-Gly has the capability to activate the proliferation of lymphocytes in thymus during its aging. The nucleotide sequence which is complementary contacted with peptide Ala-Glu-Asp-Gly was found in promoter region of interferon gamma gene. Thus, the immune protection of this peptide can be explained by its activation of the interferon gamma production in T-cells.