Rbpj expression in regulatory T cells is critical for restraining TH2 responses [spleen RbpjKO sick expression]

The transcriptional regulator Rbpj is involved in T-helper (TH) subset polarization, but its function in Treg cells remains unclear. Here we show that Treg-specific Rbpj deletion leads to splenomegaly and lymphadenopathy despite increased numbers of Treg cells with a polyclonal TCR repertoire. A specific defect of Rbpj-deficient Treg cells in controlling TH2 polarization and B cell responses was observed, leading to the spontaneous formation of germinal centers and a TH2-associated immunoglobulin class switch as well as T-cell polarization into TH2 effector cells. The observed phenotype was environment-dependent and could be induced by infection with parasitic nematodes. Rbpj-deficient Treg cells adopted open chromatin landscapes and gene expression profiles reminiscent of tissue-derived TH2-polarized Treg cells, with a prevailing footprint of transcription factor Gata-3. The over-expression of Ilt3 rendered Rbpj-deficient Treg cells incompatible to specifically restrain TH2 responses, finally leading to severe and fatal lymphoproliferative disease. We isolated spleen cells from affected Treg Rbpj-deficient animals and wildtype counterparts. Cells were stained with antibodies and cell populations sorted by FACS. Total RNA was isolated and measured with gene expression microarry.