Shifting phenotype and differentiation of CD11b+Gr.1+ immature heterogeneous myeloid derived adjuster cells support inflammation and induce regulators of IL17A in imiquimod induced psoriasis.

Objective and design: The exact immunological mechanism of widespread chronic inflammatory skin disorder psoriasis has not been fully established. CD11b⁺Gr.1⁺ myeloid-derived cells are immature heterogeneous cells with T-cell suppressive property in neoplasia; however, influence of these cells on adaptive immunity is highly contextual; therefore, we dubbed these cells as myeloid-derived adjuster cells (MDAC). We studied imiquimod induced psoriasis in mouse model and evaluated for the first time the RORγt-NFAT1 axis in MDACs and the function, differentiation and interaction of these cells with T cells.

Materials and methods: The status of T cells and MDACs; their functionality and differentiation properties, and the roles of RORγt and NFAT1 in MDACs were evaluated using flow cytometry, qRT-PCR and confocal imaging.

Results: We found gradual increase in T cells and MDACs and an increase in the number of IL17 -secreting MDACs and T cells in the skin of psoriatic animals. We also noted that MDAC differentiation is biased toward M1 macrophages and DCs which perpetuate inflammation. We found that psoriatic MDACs were unable to suppress T-cell proliferation or activation but seemingly helped these T cells produce more IL17. Inhibition of the RORγt/NFAT1 axis in MDACs increased the suppressive nature of MDACs, allowing these cells to suppress the activity of psoriatic T-cells.

Conclusion: Our results indicate that altered MDAC properties in psoriatic condition sustains pathological inflammation and RORγt and NFAT1 as promising intervention target for psoriasis management.