IN THIS ISSUE

doi:10.4049/jimmunol.177.12.8281

T Cells in Innate Immunity

⇓ The observation that STAT proteins are crucial in innate immunity during septic peritonitis in mice prompted Watanabe et al. (p. 8650 ) to look at the role of suppressors of cytokine signaling (SOCS) proteins in attenuating responses of cytokines that act through the JAK/STAT pathway. They found that mice transgenic for SOCS5 (SOCS5Tg) had higher survival rates and increased bacterial clearance after sepsis induced by cecal ligation and puncture (CLP) than wild-type controls; transgenic neutrophils and macrophages infected in vitro produced more superoxide and killed more bacteria than wild-type cells. SOCS5Tg mice had greater infiltration of peritoneal leukocytes with reduced STAT6 phosphorylation and had higher IL-12, IFN-γ, and TNF-α levels in peritoneal exudates after CLP. Wild-type phagocytes cocultured with transgenic CD4⁺ T cells killed more bacteria than phagocytes cocultured with wild-type CD4⁺ T cells. RAG^−/− mice adoptively transferred with CD4⁺ T cells before CLP had more peritoneal leukocytes and fewer bacteria than mice given wild-type cells. Anti-IFN-γ Ab abrogated the increased LPS-stimulated production of TNF-α of wild-type macrophages cocultivated with SOCS5Tg vs wild-type CD4⁺ T cells. Transgenic mice had more peripheral memory T cells and fewer naive T cells than controls. Histological examination of SOCS5Tg kidneys after CLP revealed minimal damage. The authors propose that CD4⁺ T cells overexpressing SOCS5 protein enhance innate immune responses during CLP by IFN-γ-induced activation of leukocytes.

HOSCN-Amplified Inflammation

Among the stable oxidants produced by neutrophil myeloperoxidase and eosinophil peroxidase, only the weakly reactive hypothiocyanous acid (HOSCN) enters mammalian cells to induce tissue factor expression. Wang et al. (p. 8714 ) found that HUVEC treated with HOSCN or LPS had increased mRNA and protein expression of several adhesion molecules whose genes contain upstream p65/p50 NF-κB binding sites compared with untreated cells or cells treated with other neutrophil or eosinophil oxidants. The up-regulation was abolished in cells pretreated with a specific NF-κB pathway inhibitor, whereas a PI3K/Akt pathway inhibitor enhanced baseline and HOSCN-stimulated adhesion molecule expression and suppressed Akt phosphorylation. EMSA and Ab supershift assays confirmed p65/p50 activation in nuclear extracts of HOSCN-treated cells. In vitro static adhesion assays demonstrated increased binding of neutrophils and eosinophils to HOSCN-treated HUVEC vs LPS-treated controls, and anti-adhesion molecule Abs blocked the binding. Mice injected i.p. with HOSCN had an 8-fold increase over baseline in neutrophil accumulation in their peritoneal cavities. Activation of other proinflammatory transcription factors in HOSCN-treated HUVEC was detected by microarray analyses. The authors propose that transcriptional induction of endothelial cell adhesion molecules by phagocyte oxidant HOSCN-mediated NF-κB pathway activation might contribute to the pathophysiology of atherogenesis.

Prostate Cancer Cells Get MIFfed

Inflammation of prostate cells due to overexpression of the proinflammatory cytokine, macrophage migration inhibitory factor (MIF), may contribute to prostate cancer. In a continuation of their study of MIF interaction with its receptor CD74 and its signaling component CD44, Meyer-Siegler et al. (p. 8730 ) showed that invasive androgen-independent prostate cancer cells express more of each of the three interacting proteins than noninvasive cancer or benign prostate cells. A MIF antagonist blocked MIF bioactivity in cell lysates and culture media from the three prostate cell types; proliferation of the androgen-independent cells, the only cells with CD74 surface expression, was also blocked. Anti-MIF or anti-CD74 Abs inhibited proliferation and induced apoptosis in the androgen-independent cells and reduced their invasion in Matrigel assays but had no effect on control cells. Transfection with MIF or CD74 interfering RNAs (RNAis) induced apoptosis and reduced ERK1/2 activation only in the androgen-independent cells. Decreased expression of genes associated with apoptosis and cell cycle regulation were seen in targeted array analyses on MIF and/or CD74 RNAi-treated androgen-independent prostate cells. Sizes of tumors were significantly smaller in mice carrying androgen-independent xenografts injected with the MIF antagonist compared with untreated controls. The experiments demonstrate that MIF/cell surface CD74 interactions are important in androgen-independent prostate cancer and can be blocked by Abs and RNAis against them.

SNPing Away at Asthma

⇓ Human susceptibility to allergic inflammation is associated with a single nucleotide polymorphism (SNP) of C to T at base 1112 within the IL13 gene promoter. However, extensive linkage disequilibrium within the IL13 locus precludes a genetic epidemiological approach using SNPs to analyze disease risk. Cameron et al. (p. 8633 ) showed that a reporter construct driven by the IL13 promoter containing 1112T was less active in activated primary or established human T cells but was more active in activatedpolarized primary human Th2 cells than the wild-type promoter. Both alleles bound STAT1/STAT6 in EMSA using nuclear extracts from activated primary Th2 cells, but supershift assays showed that only the 1112T mutant allele bound transcription factor Yin-Yang 1 (YY1) in both resting and activated Th2 cells. Whereas the wild-type allele in activated primary and established T cells bound STAT1/STAT6 and STAT1, respectively, the mutant allele also bound YY1 plus an additional, but different, transcription factor in primary vs established T cells. Wild-type, but not mutant, promoter activity was decreased by STAT6 overexpression in activated T cells. Anti-STAT6 or anti-YY1 Abs coprecipitated the 1112T-containing promoter in chromatin immunoprecipitation assays on Th2 extracts. Higher levels of IL-13 were produced by activated PBMCs from women in the third trimester of pregnancy who were homozygous for the IL13 promoter T mutation compared with heterozygous or wild-type controls. The authors use functional assays to demonstrate that a SNP in the IL13 promoter has opposite effects in activated human T vs Th2 lymphocytes due to different patterns of transcription factor binding.

Treating Autoimmune Prostatitis

⇓ The activated form of vitamin D and other vitamin D receptor (VDR) agonists are used to prevent or treat a variety of experimental autoimmune and inflammatory conditions in animal disease models. Treatment of benign prostatic hyperplasia in humans with the VDR agonist, Elocalcitol, is in clinical trial. However, the effect of VDR agonists on autoimmune prostatitis has not been studied. Penna et al. (p. 8504 ) found 67% fewer intraprostatic infiltrates in Elocalcitol-treated NOD mice previously injected with prostate homogenate compared with vehicle-treated controls. Elocalcitol also reduced leukocyte infiltrates in components of the prostate peripheral nervous system, increased apoptosis in prostate-infiltrating and resident epithelial and stromal prostate cells, reduced inducible NO synthase expression and NO production in peritoneal macrophages, and decreased IFN-γ and IL-17 production by lymph node cells stimulated in vitro. IFN-γ production by lymph node cells from Elocalcitol-treated NOD mice immunized with an immunodominant epitope of prostatic steroid binding protein was less than that of cells from vehicle-treated immunized animals after in vitro stimulation with peptide or native protein. Prostatic infiltration and type 1 diabetes were significantly reduced in NOD.SCID recipients given CD4⁺ T cells from Elocalcitol-treated NOD mice. The data show that the VDR agonist Elocalcitol reduces experimental autoimmune prostatitis and inhibits CD4⁺ T cell responses in a NOD mouse model.

T Cell Responses to Dual Pathogens

Granulomas formed by CD4⁺ T cells control chronic mycobacterial infections. However, the impact of a concurrent CD4⁺ T cell response to an acute viral infection on the chronic bacterial infection has not been explored. Co et al. (p. 8456 ) developed a two transgenic (Tg) T cell model. RAG^−/− mice expressing a monoclonal T cell population specific for an epitope tag on a recombinant mycobacterium were infected with tagged bacteria and adoptively transferred with spleen cells from mice transgenic for a different tag specific for a recombinant influenza virus. Mycobacteria and virus localized to liver and lung, respectively, and induced inflammation and specific T cell expansion primarily in their target organs. But recombinant virus infection of the bacteria-infected transgenic RAG^−/− mice increased the number of activated IFN-γ-secreting virus-specific T cells in lungs and in liver granulomas and reduced the proportion of activated IFN-γ-secreting bacteria-specific T cells at those sites compared with wild-type influenza virus infection. At the same time, recombinant virus up-regulated MHC class II expression on granuloma-infiltrating macrophages. In contrast, bacteria infection activated bacteria-specific T cells only in granulomas. Animals infected with wild-type or recombinant virus had more granulomas but were not impaired in their ability to control their bacterial infections. This use of two monoclonal T cell populations specific for different and anatomically separated infections demonstrate that a secondary acute influenza virus infection does not interfere with, but can modulate, mycobacteria-specific T cell function in a chronic infection, possibly by competition between the two different T cell populations.

Scavenging Hsp70-Peptide Complexes

⇓ Heat shock protein 70 (Hsp70) acts as a chaperone for tumor Ags and releases Hsp70-peptide complexes that can induce tumor immunity by cross-presentation of tumor Ags to T cells. The observation that Hsp70 binds to one scavenger receptor (SR) family member led Thériault et al. (p. 8604 ) to show that Hsp70-peptide complexes from human tumor cells bind to hamster cells each transfected with one of three SR family members but not to nontransfected hamster cells. Binding to SRs was greater with Hsp70-peptide complexes from tumor cells than with recombinant Hsp70, and recombinant Hsp70 had greater binding if complexed with ADP vs ATP. Hsp70-peptide complexes also bound to cells transfected with some members of the c-type lectin receptor family. Labeled Hsp70 was visualized in vesicles of fixed cells by fluorescence microscopy. SR mutants deleted for all or some of their intracellular domains or an extracellular di-leucine motif internalized the tumor cell Hsp70-peptide complexes. The authors demonstrate binding of tumor cell Hsp70-peptide complexes to SR and c-type lectin family members and show that internalization is independent of the SR intracellular domain.