Bacterial Killing Activity of Polymorphonuclear Myeloid-Derived Suppressor Cells Isolated From Tumor-Bearing Dogs

• Published in: Frontiers in immunology Vol. 10; p. 2371
• Main Authors: Hlavaty, Sabina I, Chang, Yu-Mei, Orth, Rachel P, Goulian, Mark, Planet, Paul J, Thamm, Douglas H, Punt, Jennifer A, Garden, Oliver A
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 10.10.2019
• Subjects: Animals; bactericidal; cancer; canine; Dog Diseases - immunology; Dog Diseases - pathology; Dogs; Escherichia coli - immunology; Female; G-MDSC; Immunity, Cellular; Immunology; Male; MDSC; Myeloid-Derived Suppressor Cells - immunology; Myeloid-Derived Suppressor Cells - pathology; Neoplasms - immunology; Neoplasms - pathology; Neoplasms - veterinary; PMN-MDSC; Staphylococcus aureus - immunology; phagocytosis; MDSC; PMN-MDSC; reactive oxygen species; cancer; canine; G-MDSC; bactericidal
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2019.02371

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 ( ) 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 ( ) 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.