%A Hlavaty,Sabina I. %A Chang,Yu-Mei %A Orth,Rachel P. %A Goulian,Mark %A Planet,Paul J. %A Thamm,Douglas H. %A Punt,Jennifer A. %A Garden,Oliver A. %D 2019 %J Frontiers in Immunology %C %F %G English %K MDSC,PMN-MDSC,canine,Cancer,Bacteria,Killing,Phagocytosis,Reactive Oxygen Species,E. coli,S. aureus,G-MDSC, granulocytic MDSC %Q %R 10.3389/fimmu.2019.02371 %W %L %M %P %7 %8 2019-October-10 %9 Original Research %# %! Bacterial killing activity of PMN-MDSCs isolated from tumor-bearing dogs %* %< %T Bacterial Killing Activity of Polymorphonuclear Myeloid-Derived Suppressor Cells Isolated From Tumor-Bearing Dogs %U https://www.frontiersin.org/articles/10.3389/fimmu.2019.02371 %V 10 %0 JOURNAL ARTICLE %@ 1664-3224 %X Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are implicated in the progression and outcome of a variety of pathological states, from cancer to infection. Our previous work has identified three antimicrobial peptides differentially expressed by PMN-MDSCs compared to conventional neutrophils isolated from dogs, mice, and human patients with cancer. We therefore hypothesized that PMN-MDSCs in dogs with cancer possess antimicrobial activity. In the current work, we observed that exposure of PMN-MDSCs to Gram-negative bacteria (Escherichia coli) increased the expression of reactive oxygen species by the PMN-MDSCs, indicating that they are capable of initiating an anti-microbial response. Electron microscopy revealed that the PMN-MDSCs phagocytosed Gram-negative and Gram-positive (Staphylococcus aureus) bacterial species. Lysis of bacteria within some of the PMN-MDSCs suggested bactericidal activity, which was confirmed by the recovery of significantly lower numbers of bacteria of both species following exposure to PMN-MDSCs isolated from tumor-bearing dogs. Our data therefore indicate that PMN-MDSCs isolated from dogs with cancer, in common with PMNs, have phagocytic and bactericidal activity. This nexus of immunosuppressive and antimicrobial activity reveals a hitherto unrecognized function of MDSCs.