Blimp‐1 is expressed in human and mouse T cell subsets and leads to loss of IL‐2 production and to defective proliferation

The transcriptional repressor Blimp-1 regulates terminal differentiation of B-lymphocytes and myeloid cells. We now show that Blimp-1 is also expressed in human and murine primary T lymphocytes. Blimp-1 expression is highest in freshly isolated primary T cells with an antigen experienced phenotype. Th2 and CD4+CD25+ cells exhibited higher levels of Blimp-1 mRNA than Th1 cells. However, ectopic expression of Blimp-1 by retroviral transduction neither altered the frequency of IFN-γ or IL-4 producing cells nor did it induce suppressor activity. In non-polarized cells, retroviral transduction of Blimp-1 led to a marked reduction in IL-2 secretion, to an inability to proliferate and to reduced viability. Our data suggest that Blimp-1 is physiologically expressed in T lymphocytes during late stages of differentiation, induces down regulation of IL-2 production and a shortened life span and might thus contribute to a limitation of T cell immune responses.