Defensins contribute to host defense by disrupting the cytoplasmic membrane of microorganisms. This report shows that human beta-defensins are also chemotactic for immature dendritic cells and memory T cells. Human beta-defensin was selectively chemotactic for cells stably transfected to express human CCR6, a chemokine receptor preferentially expressed by immature dendritic cells and memory T cells. The beta-defensin-induced chemotaxis was sensitive to pertussis toxin and inhibited by antibodies to CCR6. The binding of iodinated LARC, the chemokine ligand for CCR6, to CCR6-transfected cells was competitively displaced by beta-defensin. Thus, beta-defensins may promote adaptive immune responses by recruiting dendritic and T cells to the site of microbial invasion through interaction with CCR6.

SummaryThioredoxin (Trx) is a ubiquitous intracellular protein disulfide oxidoreductase with a CXXC active site that can be released by various cell types upon activation. We show here that Trx is chemotactic for monocytes, polymorphonuclear leukocytes, and T lymphocytes, both in vitro in the standard micro Boyden chamber migration assay and in vivo in the mouse air pouch model. The potency of the chemotactic action of Trx for all leukocyte populations is in the nanomolar range, comparable with that of known chemokines. However, Trx does not increase intracellular Ca 2 ϩ and its activity is not inhibited by pertussis toxin. Thus, the chemotactic action of Trx differs from that of known chemokines in that it is G protein independent. Mutation of the active site cysteines resulted in loss of chemotactic activity, suggesting that the latter is mediated by the enzyme activity of Trx. Trx also accounted for part of the chemotactic activity released by human T lymphotropic virus (HTLV)-1-infected cells, which was inhibited by incubation with anti-Trx antibody. Since Trx production is induced by oxidants, it represents a link between oxidative stress and inflammation that is of particular interest because circulating Trx levels are elevated in inflammatory diseases and HIV infection.

The chemokines use G protein-coupled receptors to regulate the migratory and proadhesive responses of leukocytes. Based on observations that G protein-coupled receptors undergo heterologous desensitization, we have examined the ability of chemokines to also influence the perception of pain by cross-desensitizing opioid G protein-coupled receptors function in vitro and in vivo. We find that the chemotactic activities of both -and ␦-opioid receptors are desensitized following activation of the chemokine receptors CCR5, CCR2, CCR7, and CXCR4 but not of the CXCR1 or CXCR2 receptors. Furthermore, we also find that pretreatment with RAN-TES͞CCL5, the ligand for CCR1, and CCR5 or SDF-1␣͞CXCL12, the ligand for CXCR4, followed by opioid administration into the periaqueductal gray matter of the brain results in an increased rat tail flick response to a painful stimulus. Because chemokine administration into the periaqueductal gray matter inhibits opioidinduced analgesia, we propose that the activation of proinflammatory chemokine receptors down-regulates the analgesic functions of opioid receptors, and this enhances the perception of pain at inflammatory sites. O pioid and chemokine receptors are members of the G i protein-linked seven-transmembrane receptor family. These receptors, as well as the chemokine and endogenous opioid peptide ligands, are widely distributed in brain tissue and the periphery. Chemokines have been classified into four families: C, CC, CXC, and CX 3 C based on the position of conserved cysteines, and they interact with receptors designated CR1, CCR1-11, CXCR1-5, or CX 3 CR1, respectively (1). Three classes of receptors have been identified for the opioids, designated , , and ␦, and each of the opioid receptor genes expressed in brain tissue and immune cells has been cloned and sequenced (2-7).The -, -, and ␦-opioids are known to have inhibitory effects on both antibody and cellular immune responses (8, 9), natural killer cell activity (10), cytokine expression (11-13), and phagocytic activity (14), which may account for the decreased resistance to infections caused by morphine and heroin administration. Furthermore, pretreatment with opioids, including morphine, heroin, met-enkephalin, the selective -agonist ]enkephalin (DPDPE), leads to the inhibition of the chemotactic response of leukocytes to complement-derived chemotactic factors (15) and to the chemokines macrophage inflammatory protein (MIP-1␣)͞CCL3, regulated on activation normal T cell expressed and secreted (RANTES͞CCL5), monocyte chemotactic protein-1 (MCP-1)͞ CCL2, and IL-8͞CXCL8 (16). The latter results suggest that the activation of the -and ␦-opioid receptors leads to the desensitization of the CC chemokine receptor 2 (CCR2) and CXC chemokine receptors CXCR1 and CXCR2. In fact, the latter two receptors are phosphorylated by prior administration of opioids. Moreover, the inhibition of CCL3 and CCL5 responses following opioid pretreatment is consistent with the desensitization of either CCR1 or CCR5, or both. This receptor crosstalk r...

Reciprocal differentiation of immunosuppressive CD4 + CD25 + FoxP3 + T regulatory cells (Tregs) and proinflammatory IL-17-producing cells (Th17) from naïve CD4 cells is contingent upon the cytokine environment. Using MACS-purified CD4 cells, we found that rapamycin and cyclosporine A (CsA) potently inhibited the TGFβ and IL-6-induced generation of IL-17-producing cells. Intriguingly, rapamycin promoted, while CsA markedly inhibited, TGFβ-mediated generation of Tregs. The aforementioned effects of rapamycin and CsA were also observed for Flow-sorted CD4+CD25− T cells, indicating that the effect of these two immunosuppressive agents was based on their action on de novo generation of Tregs and Th17 cells from naïve CD4 cells. Our observation suggests a distinct mode of immunosuppressive action and tolerance induction by rapamycin and CsA. The capacity of rapamycin to generate immunosuppressive Tregs and to suppress differentiation of pathogenic Th17 cells furthers our understanding of the basis for the therapeutic immunosuppressive effects of rapamycin in patients with autoimmune diseases and allo-transplantation reactions.

Macrophage infiltration into inflammatory sites is generally preceded by neutrophils. This suggests neutrophils may be the source of chemotactic factors for monocytes. To identify these putative monocyte attractants, we have systematically prepared neutrophil granules, lysed them, and sequentially purified the released proteins by several reverse phase chromatography procedures. Assays for monocyte chemotactic activity of the chromatography fractions yielded a major peak of activity associated with a protein of 30 kD, according to SDS-PAGE analysis. NH2-terminal sequence of the protein revealed this to be identical to cathepsin G. The monocyte chemotactic activity of human cathepsin G was dose dependent with optimal concentration at 0.5–1 μg/ml. Cathepsin G is chemotactic rather than chemokinetic for monocytes, as demonstrated by checkerboard analysis. Cathepsin G–induced monocyte chemotaxis is partially pertussis toxin sensitive implying the involvement of a G protein–coupled receptor. Enzymatic activity of cathepsin G is associated with its monocyte chemotactic activity, since DFP- or PMSF-inactivated cathepsin G no longer induced monocyte migration. The chemotactic activity of cathepsin G can also be completely blocked by α1 antichymotrypsin, a specific inhibitor of chymotrypsin-like proteinases present in human plasma. In addition, cathepsin G is also a potent chemoattractant for neutrophils and a chemokinetic stimulant for T cells. In the course of pursuing these in vitro studies, we established that the T cell chemoattractant, azurocidin/CAP37 from human neutrophil granules, at doses of 0.05 to 5 μg/ml, was chemotactic for monocytes and neutrophils. As predicted from the in vitro chemotactic activity, subcutaneous injection of cathepsin G into BALB/c mice led to infiltration of both mononuclear cells and neutrophils. Thus, the transition of inflammatory exudate from neutrophil to mononuclear cells can be mediated, at least in part, by extracellular release of neutrophil granule proteins such as cathepsin G and azurocidin/CAP37.

Summary Previously we found that co-expression of CD25 and TNFR2 identified the most suppressive subset of mouse regulatory T cells (Tregs). Here, we report that human peripheral blood (PB) FoxP3+ cells present in CD25high, CD25low and even CD25− subsets of CD4 cells expressed high levels of TNFR2. Consequently, TNFR2-expressing CD4+CD25+ Tregs included all of FoxP3+ cells present in CD4+CD25high subset as well as a substantial proportion of FoxP3+ cells present in CD4+CD25low subset. CD4+CD25+TNFR2+ cells identified 5-fold greater number of PB CD4 lymphocytes as Tregs than identified by CD4+CD25high cells, and expressed comparable levels of FoxP3+ cells as reported CD4+CD25+CD127low/− Tregs. Furthermore, this population of cells exhibited the characteristic Treg phenotype, including expression of high levels of CTLA-4, CD45RO, CCR4 and low levels of CD45RA and CD127. Upon TCR stimulation, human PB CD4+CD25+TNFR2+ cells were anergic and markedly inhibited the proliferation and cytokine production of co-cultured T responder cells. In contrast, CD4+CD25+TNFR2− and CD4+CD25− TNFR2+ T cells did not show inhibitory activity. Since some non-Tregs express TNFR2, the combination of CD25 and TNFR2 must be used to identify larger population of human Tregs, which may prove to be of diagnostic and therapeutic benefit in cancer and autoimmune diseases.

An intact chemotactic response is vital for leukocyte trafficking and host defense. Opiates are known to exert a number of immunomodulating effects in vitro and in vivo, and we sought to determine whether they were capable of inhibiting chemokine-induced directional migration of human leukocytes, and if so, to ascertain the mechanism involved. The endogenous opioid met-enkephalin induced monocyte chemotaxis in a pertussis toxin–sensitive manner. Met-enkephalin, as well as morphine, inhibited IL-8–induced chemotaxis of human neutrophils and macrophage inflammatory protein (MIP)-1α, regulated upon activation, normal T expressed and secreted (RANTES), and monocyte chemoattractant protein 1, but not MIP-1β–induced chemotaxis of human monocytes. This inhibition of chemotaxis was mediated by δ and μ but not κ G protein–coupled opiate receptors. Calcium flux induced by chemokines was unaffected by met-enkephalin pretreatment. Unlike other opiate-induced changes in leukocyte function, the inhibition of chemotaxis was not mediated by nitric oxide. Opiates induced phosphorylation of the chemokine receptors CXCR1 and CXCR2, but neither induced internalization of chemokine receptors nor perturbed chemokine binding. Thus, inhibition of chemokine-induced chemotaxis by opiates is due to heterologous desensitization through phosphorylation of chemokine receptors. This may contribute to the defects in host defense seen with opiate abuse and has important implications for immunomodulation induced by several endogenous neuropeptides which act through G protein–coupled receptors.

FPR is expressed by highly malignant human glioma cells and appears to mediate motility, growth, and angiogenesis of human glioblastoma by interacting with host-derived agonists. Thus, FPR may represent a molecular target for the development of novel antiglioma therapeutics.