[Myeloid-derived Gr-1⁺ CD11b⁺ suppressor cells are involved in immunoregulation of experimental autoimmune...

To explore the change in the number and role of Gr-1⁺ CD11b⁺ myeloid-derived suppressor cells (MDSCs) in experimental autoimmune encephalomyelitis (EAE).

Totally 30 healthy female C57BL/6 mice were randomly divided into two groups: EAE-induced group (n=15) and control group (n=15). EAE was induced by immunization with myelin oligodendrocyte glycoprotein peptide 35-55 (MOG35-55), and pathological changes in spinal cords were revealed by HE staining and Luxol fast blue (LFB) staining. The number of Gr-1⁺ CD11b⁺ MDSCs in spleens and spinal cords of the two groups was respectively compared by flow cytometry and immunofluorescent staining. The effect of Gr-1⁺ CD11b⁺ MDSCs from EAE mice on the proliferation of CD4⁺ T cells and CD8⁺ T cells was evaluated by in vitro co-culture system.

Twelve of 15 immunized mice (80%) developed EAE. HE staining showed an extensive infiltration of inflammatory cells in the spinal cords of the EAE mice. LFB staining revealed multiple demyelinated lesions in the above inflammatory infiltration. The immunofluorescent histochemistry suggested that many Gr-1⁺ CD11b⁺ MDSCs were present in spinal cords of the EAE mice, but no positive cells were observed in the control group. The mass of spleen in the EAE mice was significantly higher than that of the control mice [(146.5 ± 12.4) mg vs (67.2 ± 8.7) mg, P<0.01], and the proportion of splenic Gr-1⁺ CD11b⁺ MDSCs in EAE mice significantly increased (P<0.01 vs controls). Consistent with the results of immunofluorescent staining, a significantly increased proportion of Gr-1⁺ CD11b⁺ MDSCs in spinal cords of EAE mice was observed with flow cytometry. In vitro co-culture analysis revealed that Gr-1⁺ CD11b⁺ MDSCs from spinal cords of the EAE mice markedly suppressed the proliferation of CD4⁺ T cells and CD8⁺ T cells.

EAE induces an expansion and aggregation of Gr-1⁺ CD11b⁺ MDSCs in spleens and spinal cords. These cells suppress T cell proliferation in vitro and are involved in the immunoregulation of EAE.