Interferon-α is a potent antiviral agent and a vigorous adjuvant in the induction of T-cell responses but its use is limited by hematologic toxicity. Interferon-α alters hematopoietic stem cell dormancy and impairs myelocytic and erythrocytic/megakaryocytic differentiation from hematopoietic progenitors. However, the effect of chronic interferon-α exposure on hematopoietic precursors has still not been well characterized. Here, we transduced the liver of mice with an adenoassociated vector encoding interferon-α to achieve sustained high serum levels of the cytokine. The bone marrow of these animals showed diminished long-term and short-term hematopoietic stem cells, reduction of multipotent progenitor cells, and marked decrease of B cells, but significant increase in the proportion of CD8(+) and CD4(+)CD8(+) T cells. Upon adoptive transfer to RAG(-/-) mice, bone marrow cells from interferon-α-treated animals generated CD4(+) and CD8(+) T cells while CD19(+), CD11b(+) and NK1.1(+) lineages failed to develop. These effects are associated with the transcriptional downregulation of transcription factors involved in B-cell differentiation and modulation of key factors for T-cell development. Thus, sustained interferon-α exposure causes hematopoietic stem cells exhaustion and drives common lymphoid progenitors towards T-cell generation.
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