CD11b+Ly6C++Ly6G- cells show distinct function in mice with chronic inflammation or tumor burden
Immunology Group, Lund University and Active Biotech AB*, BMC D14, SE-22184, Lund, Sweden
BMC Immunology 2012, 13:69 doi:10.1186/1471-2172-13-69Published: 12 December 2012
S100A9 has been shown to be important for the function of so called Myeloid Derived Suppressor Cells (MDSC). Cells with a similar phenotype are also involved in pro-inflammatory processes, and we therefore wanted to investigate the gene expression and function of these cells in animals that were either subjected to chronic inflammation, or inoculated with tumors.
CD11b+Ly6C++ and Ly6G+ cells were isolated from spleen, tumor tissue or inflammatory granulomas. S100A9, Arginase 1 and iNOS gene expression in the various CD11b+ cell populations was analyzed using Q-PCR. The suppressive activity of the CD11b+ cell populations from different donors was studied in co-culture experiments.
S100A9 was shown to be expressed mainly in splenic CD11b+Ly6C+G+ cells both at the RNA and protein level. Arginase I and iNOS expression could be detected in both CD11b+Ly6C+Ly6G+ and CD11b+Ly6C+G-/C++G- derived from tumors or a site of chronic inflammation, but was very low in the same cell populations isolated from the spleen. CD11b+ cells isolated from mice with peritoneal chronic inflammation were able to stimulate T lymphocytes, while CD11b+ cells from mice with peritoneal tumors suppressed T cell growth.
An identical CD11b+Ly6C++G- cell population appears to have the ability to adopt immune stimulatory or immune suppressive functions dependent on the presence of a local inflammatory or tumor microenvironment. Thus, there is a functional plasticity in the CD11b+Ly6C++G- cell population that cannot be distinguished with the current molecular markers.