The Myeloid Receptor PILRβ Mediates the Balance of Inflammatory Responses through Regulation of IL-27 Production

Paired immunoglobulin-like receptors beta, PILRβ, and alpha, PILRα, are related to the Siglec family of receptors and are expressed primarily on cells of the myeloid lineage. PILRβ is a DAP12 binding partner expressed on both human and mouse myeloid cells. The potential ligand, CD99, is found on many cell types, such as epithelial cells where it plays a role in migration of immune cells to sites of inflammation. Pilrb deficient mice were challenged with the parasite Toxoplasma gondii in two different models of infection induced inflammation; one involving the establishment of chronic encephalitis and a second mimicking inflammatory bowel disease in order to understand the potential role of this receptor in persistent inflammatory responses. It was found that in the absence of activating signals from PILRβ, antigen-presenting cells (APCs) produced increased amounts of IL-27, p28 and promoted IL-10 production in effector T cells. The sustained production of IL-27 led ultimately to enhanced survival after challenge due to dampened immune pathology in the gut. Similar protection was also observed in the CNS during chronic T. gondii infection after i.p. challenge again providing evidence that PILRβ is important for regulating aberrant inflammatory responses

doi:10.1093/nar/gkn271 In vivo identification of novel STAT5 target genes

STAT5A and STAT5B proteins belong to the family of signal transducers and activators of transcription. They are encoded by two separate genes with 91% identity in their amino acid sequences. Despite their high degree of conservation, STAT5A and STAT5B exert non-redundant functions, resulting at least in part from differences in target gene activation. To better characterize the differential contribution of STAT5A and STAT5B in gene regulation, we performed single or double knockdown of STAT5A and STAT5B using small interfering RNA. Subsequent gene expression profiling and RT-qPCR analyses of IL-3-stimulated Ba/F3-b cells led to the identification of putative novel STAT5 target genes. Chromatin immunoprecipitation assays analyzing the corresponding gene loci identified unusual STAT5 binding sites compared to conventional STAT5 responsive elements. Some of the STAT5 targets identified are upregulated in several human cancers, suggesting that they might represent potential oncogenes in STAT5-associated malignancies

Modulation of Paired Immunoglobulin-Like Type 2 Receptor Signaling Alters the Host Response to Staphylococcus aureus-Induced Pneumonia ▿ †

Paired immunoglobulin-like type 2 receptors (PILRs) inhibitory PILRα and activating PILRβ are predominantly expressed on myeloid cells. Their functions in host defense and inflammation are largely unknown, and in this study, we evaluated their roles in an acute Staphylococcus aureus pneumonia model. Compared to their respective controls, Pilrb−/− mice or mice in which PILRα was activated with an agonistic antibody showed improved clearance of pulmonary staphylococci and improved survival. These mice had reduced serum or bronchoalveolar lavage fluid levels of interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and IL-6 and elevated levels of gamma interferon (IFN-γ), IL-12, and IL-10. In contrast, mice in which PILRβ was activated had increased lung bacterial burdens and higher mortality coupled with an intense proinflammatory response with highly elevated levels of IL-1β, TNF-α, and IL-6. Treatment groups with reduced bacterial burdens had higher levels of Keratinocyte-derived chemokine (KC), macrophage inflammatory protein 2 (MIP-2), and MIP-1α in bronchoalveolar lavage fluid and an increased influx of neutrophils and macrophages to the lungs. Consistent with our in vivo findings, bone marrow-derived macrophages from Pilrb−/− mice released significantly less IL-1β and TNF-α and more IFN-γ and IL-12 than did the wild-type macrophages when directly stimulated with heat-killed S. aureus. To our knowledge, this is the first evidence that S. aureus directly interacts with PILRβ. It provides a mechanism by which manipulating the balance in favor of an inhibitory PILR signal, by activation of PILRα or deletion of PILRβ, helps to control acute S. aureus-mediated pneumonia and attenuate the inflammatory response. These results highlight the importance of PILRs in innate immunity and the control of inflammation

Host survival is characterized by increased capacity to produce IL-27p28.

<p>Recall assays using MLNs at day 5 (a); and splenocytes at day 7 (b and c, left panels) or day 10 (b and c, right panels) after peroral challenge. Amount of IFNγ (a, top graph; and b, left and right) or IL-10 (a, bottom graph; and c, left and right) detectable in supernatants of WT (grey bars) and <i>Pilrb−/−</i> (black bars) after 3 days of culture in media alone, with STAg, or with αCD3. For panel a, one representative experiment of two shown; for panels b and c, combined data from 3 independent experiments shown. Time course of IL-27p28 protein in serum from infected WT (grey bars) and <i>Pilrb</i> −/− (black bars) mice as detected by ELISA, mean ± SD is shown (d). Values between strains on days 5, p = 0.0219 and 7, p = 0.0318 are all significantly different. Recall assay using MLNs at day 5 post-peroral infection and cultured as above. Amount of IL-27p28 detectable in supernatants after 3 days of culture (e). Mean ± SD are shown. For STAg, p = 0.0143; for αCD3, p = 0.0371.</p

Cytokine mRNA expression in dendritic cells and macrophages from infected mice.

<p>Populations of DCs and macrophages were enriched from the spleens of WT and <i>Pilrb</i> −/− mice 5 days after i.p. challenge. Cells were then analyzed by RT-PCR for mRNA levels of IL27p28 (a) EBi3 (b) and IL-10 (c). Pooled data from one of two representative experiments is shown.</p

Characterization of the local inflammatory response during chronic i.p. infection.

<p>WT and <i>Pilrb</i> −/− mice were challenged i.p. with 20 cysts <i>T.gondii</i> and followed over time. Survival of WT and <i>Pilrb−/−</i> mice through 100 days post infection (a). H&E of brain sections reveal larger inflammatory foci in WT mice compared to <i>Pilrb−/−</i>, shown at 10× magnification (b). Total number of cysts present in the CNS of mice 60–90 days post infection (c). Actual numbers of BMNCs isolated from the CNS of mice (d). Recall assays using BMNCs isolated from WT and <i>Pilrb−/−</i> mice and cultured for 72 hrs in the presence of Media alone, STAg, or αCD3. Levels of protein are shown as detected by ELISA for TNFα (e), IFNγ (f), NO (g), and IL-10 (h). For panel a, n = 5–15 mice/group for each of 3 experiments performed. For panel c, pooled data from 2 experiments are shown, p<0.004. For panel d, one representative experiment of 2 is shown, p<0.05. For panels e,f, and h, pooled data from 2–3 experiments are shown, *p<0.005; **p<0.002.</p