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Objective The aim of the present paper is to study the expression and function of proton-coupled oligopeptide transporters (POTs) in spleen and macrophage, underlying their contribution to innate immune system induced by bacterial peptides, γ-iE-DAP and MDP.The quantitative real-time PCR (qRT-PCR) and western blot results revealed mRNA and protein of PepT2, PHT1, PHT2 but not PepT 1 were detected in spleen of mice and human.By comparing with the lymphocytes of the spleen, maerophages were demonstrated with higher transcript level of PepT2 and PHT2.The cellular uptake of β-Ala-Lys(AMCA) in spleen macrophages showed pH dependent with maximum uptake at pH 6.0, and with the kinetic parameters of Km and Vmax 75.5±14.3 μM and 25.4+251 pM/min per mg protein, respectively.The uptake of β-Ala-Lys(AMCA) by macrophages was not inhibited by histidine, but significantly inhibited by Giy-Sar and carnosine (P < 0.01), also by bacterial peptides, γ-iE-DAP and MDP, ligands of nucleotide-binding oligomerization domain-containing (NOD) proteins.Carnosine and Gly-Sar, but not histidine, attenuated the inflammatory response of macrophage induced by γ-iE-DAP and MDP in spleen macrophages.Moreover, reduction effect of dipeptides on immune response induced by γ-iE-DAP was also found in THP-1 cells.In conclusion, these results provide information about the functional expression of POTs in spleen, and its role in the cellular uptake of γ-iE-DAP and MDP and further contribute to innate immune system of maerophages.