Constitutively elevated levels of SOCS1 suppress innate responses in DF-1 immortalised chicken fibroblast cells.

The spontaneously immortalised DF-1 cell line is rapidly replacing its progenitor primary chicken embryo fibroblasts (CEFs) for studies on avian viruses such as avian influenza but no comprehensive study has as yet been reported comparing their innate immunity phenotypes. We conducted microarray analyses of DF-1 and CEFs, under both normal and stimulated conditions using chicken interferon-α (chIFN-α) and the attenuated infectious bursal disease virus vaccine strain PBG98. We found that DF-1 have an attenuated innate response compared to CEFs. Basal expression levels of Suppressor of Cytokine Signalling 1 (chSOCS1), a negative regulator of cytokine signalling in mammals, are 16-fold higher in DF-1 than in CEFs. The chSOCS1 “SOCS box” domain (which in mammals, interacts with an E3 ubiquitin ligase complex) is not essential for the inhibition of cytokine-induced JAK/STAT signalling activation in DF-1. Overexpression of SOCS1 in chIFN-α-stimulated DF-1 led to a relative decrease in expression of interferon-stimulated genes (ISGs; MX1 and IFIT5) and increased viral yield in response to PBG98 infection. Conversely, knockdown of SOCS1 enhanced induction of ISGs and reduced viral yield in chIFN-α-stimulated DF-1. Consequently, SOCS1 reduces induction of the IFN signalling pathway in chicken cells and can potentiate virus replication

Loss of protein tyrosine phosphatase nonreceptor type 22 regulates interferon-γ-induced signaling in human monocytes

BACKGROUND & AIMS: A gain-of-function variation within the locus that encodes protein tyrosine phosphatase nonreceptor type (PTPN)22 is associated with a reduced risk for Crohn's disease (CD), whereas a loss-of-function variant seems to promote autoimmune disorders. We investigated how loss of PTPN22 could contribute to chronic inflammation of the intestine. METHODS: Intestinal tissue samples from patients with or without inflammatory bowel disease (controls) were analyzed for levels of PTPN22 messenger RNA (mRNA) and protein. In human THP-1 monocytes, protein levels were analyzed by immunoblotting, mRNA levels by real-time polymerase chain reaction, and cytokine release by enzyme-linked immunosorbent assay. RESULTS: Intestinal tissue samples from patients with CD had reduced levels of PTPN22 mRNA and protein, compared with samples from controls. In human THP-1 monocytes, interferon-γ (IFN-γ) induced expression and activity of PTPN22. Loss of PTPN22 increased levels of p38-mitogen-activated protein kinase, but reduced phosphorylation of nuclear factor-κB subunits. Increased activity of suppressor of cytokine signaling-1 was accompanied by reduced phosphorylation of signal-transducer and activator of transcription protein 1 and signal-transducer and activator of transcription protein 3 in PTPN22-deficient cells incubated with cytokines. PTPN22 knockdown increased secretion of the inflammatory cytokines interleukin (IL)-6 and IL-17, but reduced expression or secretion of T-bet, intercellular adhesion molecule-1, nucleotide-binding oligomerization domain containing-2, monocyte chemoattractant protein-1, IL-2, and IL-12p40 in response to IFN-γ. CONCLUSIONS: PTPN22 expression is reduced in intestinal tissues of patients with active CD. PTPN22 regulates intracellular signaling events and is induced by IFN-γ in human monocytes. Knockdown of PTPN22 alters activation of inflammatory signal transducers, increasing secretion of T-helper 17-related inflammatory mediators. Genetic variants that reduce PTPN22 activity might contribute to the pathogenesis of CD by these mechanisms