Myeloid-derived suppressor cells promote immune responses after induction by alum

Objective: The present study is to study the role of myeloid-derived suppressor cells (MDSCs) in immune responses in mice and human induced by alum. Methods: CD11b+Gr1+Ly6C+Ly6G+(Ly6G-) cells were obtained by alum-induced murine model. Phenotype, endocytosis, antigen presenting ability, and T cell suppression assays were performed by flow cytometry analysis. Results: After intraperitoneal injection of alum into C57BL/6 mice, the percentage of CD11b+Gr1+ cells was increased in mice spleen and bone marrow. Compared with control mice, Ly6C, Ly6G, F4/80 and CD86 expression were higher in alum-treated mice. Alum-MDSCs showed strong antigen uptake and antigen-presentation ability, which were accompanied by increase in F4/80 molecule. In addition, proliferation of CD4+ T cells was promoted. Conclusion: The present study demonstrates that alum-induced MDSCs function as APC alone, directly prime to adoptive immune cells and trigger subsequent immune responses.