CD8+ T cells and IFN-γ induce autoimmune myelofibrosis in mice.

Myelofibrosis usually occurs either as a part of a myelodysplastic syndrome or in conjunction with neoplasia. It is not commonly thought of an autoimmune disease. We reported that p40-/-IL-2Rα-/- (interleukin-12p40 and interleukin-2 receptor alpha double knockout) mice, a mouse model of human primary biliary cholangitis, exhibited features consistent with autoimmune myelofibrosis, including anemia associated with bone marrow fibrosis, and extramedullary hematopoiesis (EMH) including LSK (Lineage-c-Kit+Sca-1+) cells in spleen, liver and peripheral blood. There were also increased LSK cells in bone marrow but they demonstrated impaired hematopoiesis. Importantly effector memory T cells that infiltrated the bone marrow of p40-/-IL-2Rα-/- mice manifested a higher ability to produce IFN-γ. CD8+ T cells, already known to play a dominate role in portal inflammation, were also key for bone marrow dysregulation and EMH. IFN-γ was the key cytokine that induced bone marrow fibrosis, bone marrow failure and EMH. Finally anti-CD8α antibody therapy fully protected p40-/-IL-2Rα-/- mice from autoimmune myelofibrosis. In conclusion, our results demonstrate that CD8+ T cells and IFN-γ are associated with autoimmune myelofibrosis, a finding that may allow targeting of CD8+ T cells and IFN-γ as a therapeutic targets.