Lymphocyte responses to chemokines

Spatiotemporal in vivo tracking of polyclonal human regulatory T cells (Tregs) reveals a role for innate immune cells in Treg transplant recruitment

Regulatory T cells (Tregs) are emerging as a new cell-based therapy in solid organ transplantation. Adoptive transfer of Tregs has been shown preclinically to protect from graft rejection, and the safety of Treg therapy has been demonstrated in clinical trials. Despite these successes, the in vivo distribution and persistence of adoptively transferred Tregs remained elusive, which hampers clinical translation. Here we isolated human Tregs using a GMP-compatible protocol and lentivirally transduced them with the human sodium iodide symporter to render them traceable in vivo by radionuclide imaging. Engineered human Tregs were characterized for phenotype, survival, suppressive capacity, and reporter function. To study their trafficking behavior, they were subsequently administered to humanized mice with human skin transplants. Traceable Tregs were quantified in skin grafts by non-invasive nano-single-photon emission computed tomography (nanoSPECT)/computed tomography (CT) for up to 40 days, and the results were validated ex vivo. Using this approach, we demonstrated that Treg trafficking to skin grafts was regulated by the presence of recipient Gr-1+ innate immune cells. We demonstrated the utility of radionuclide reporter gene-afforded quantitative Treg in vivo tracking, addressing a fundamental need in Treg therapy development and offering a clinically compatible methodology for future Treg therapy imaging in humans.

Induction of NKG2D ligand expression on tumor cells by CD8+ T-cell engagement-mediated activation of nuclear factor-kappa B and p300/CBP-associated factor

The ligands for the natural killer group 2 (NKG2D) protein render tumor cells susceptible to NKG2D-dependent immune cell attack. However, cancer cells escape from immune surveillance by downregulating NKG2D ligands. We previously discovered that engagement of activated CD8⁺ T cells and tumor cells induces NKG2D ligands on tumor cells, but the underlying mechanism remains to be defined. Both in vivo mouse tumor models and in vitro cell assays were performed to study the downstream signaling. Our results supported the notion that, upon engagement with the cognate receptors, CD137 ligand and CD40 initiates activation of nuclear factor-kappa B (NF-κB) signaling in tumor cells even in the absence of CD8⁺ T cells. Like tumor and CD8⁺ T cell contact-dependent NKG2D ligand induction, this CD137L/CD40-mediated signaling activation was associated with elevated levels of acetyltransferase P300/CBP-associated factor (PCAF), whereas inhibition of phosphorylated NF-κB abrogated PCAF induction. Although stimulation of CD137L/CD40-mediated signaling is vital, inflammatory cytokines, including interferon gamma (IFNγ) and TNFα, also facilitate NKG2D ligand–induced immune surveillance via both facilitating T cell chemotaxis and CD137L/CD40 induced NF-κB/PCAF activation. Collectively, our results unveil a novel mechanism of NKG2D ligand upregulation involving reverse signaling of CD40 and CD137L on tumor cells which, along with inflammatory cytokines IFNγ and TNFα, stimulate downstream NF-κB and PCAF activation. Understanding this mechanism may help in development of induced NKG2D ligand–dependent T cell therapy against cancers.

Characterization of the LECT2 gene and its protective effects against microbial infection via large lymphocytes in Lampetra japonica

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional protein of the innate immune system that defends against bacterial infections and chemotactic activity. However, its precise function in lamprey remains unclear. In this study, a novel LECT2 gene was first cloned from Lampetra japonica. The full-length cDNA sequence of L-LECT2 consists of a 606-bp ORF encoding a protein of 201 amino acid residues. L-LECT2 has greater than 50% sequence identity with its homologs in jawed vertebrates. FACS and immunohistochemistry assays were used to determine that the L-LECT2 protein was primarily distributed in the intestines and supraneural body tissues of lamprey, also marginally detectable in leukocytes. However, the expression of L-LECT2 was differentially upregulated in the intestines and heart after treatment with LPS. The recombinant L-LECT2 resulted in significant promoting migration of the leukocytes in vitro. Our data demonstrate that L-LECT2 treatment could enhance phagocytosis in lamprey large lymphocytes. Thus, our results suggest that LECT2 can modulate the host defense in lamprey and mediate antibacterial protection against E.coli through large lymphocytes.

Multiplex Analysis of Serum Cytokines in Humans with Hantavirus Pulmonary Syndrome

Hantavirus pulmonary syndrome (HPS) is an acute zoonotic disease transmitted primarily through inhalation of virus-contaminated aerosols. Hantavirus infection of endothelial cells leads to increased vascular permeability without a visible cytopathic effect. For this reason, it has been suggested that the pathogenesis of HPS is indirect with immune responses, such as cytokine production, playing a dominant role. In order to investigate their potential contribution to HPS pathogenesis, we analyzed the serum of hantavirus-infected subjects and healthy controls for 68 different cytokines, chemokines, angiogenic, and growth factors. Our analysis identified differential expression of cytokines that promote tissue migration of mononuclear cells including T lymphocytes, natural killer cells, and dendritic cells. Additionally, we observed a significant upregulation of cytokines known to regulate leukocyte migration and subsequent repair of lung tissue, as well as cytokines known to increase endothelial monolayer permeability and facilitate leukocyte transendothelial migration. Conversely, we observed a downregulation of cytokines associated with platelet numbers and function, consistent with the thrombocytopenia observed in subjects with HPS. This study corroborates clinical findings and extends our current knowledge regarding immunological and laboratory findings in subjects with HPS.

Human severe sepsis cytokine mixture increases β2-integrin-dependent polymorphonuclear leukocyte adhesion to cerebral microvascular endothelial cells in vitro

Introduction

Sepsis-associated encephalopathy (SAE) is a state of acute brain dysfunction in response to a systemic infection. We propose that systemic inflammation during sepsis causes increased adhesion of leukocytes to the brain microvasculature, resulting in blood-brain barrier dysfunction. Thus, our objectives were to measure inflammatory analytes in plasma of severe sepsis patients to create an experimental cytokine mixture (CM), and to use this CM to investigate the activation and interactions of polymorphonuclear leukocytes (PMN) and human cerebrovascular endothelial cells (hCMEC/D3) in vitro.

Methods

The concentrations of 41 inflammatory analytes were quantified in plasma obtained from 20 severe sepsis patients and 20 age- and sex-matched healthy controls employing an antibody microarray. Two CMs were prepared to mimic severe sepsis (SSCM) and control (CCM), and these CMs were then used for PMN and hCMEC/D3 stimulation in vitro. PMN adhesion to hCMEC/D3 was assessed under conditions of flow (shear stress 0.7 dyn/cm²).

Results

Eight inflammatory analytes elevated in plasma obtained from severe sepsis patients were used to prepare SSCM and CCM. Stimulation of PMN with SSCM led to a marked increase in PMN adhesion to hCMEC/D3, as compared to CCM. PMN adhesion was abolished with neutralizing antibodies to either β2 (CD18), α_L/β₂ (CD11α/CD18; LFA-1) or α_M/β₂ (CD11β/CD18; Mac-1) integrins. In addition, immune-neutralization of the endothelial (hCMEC/D3) cell adhesion molecule, ICAM-1 (CD54) also suppressed PMN adhesion.

Conclusions

Human SSCM up-regulates PMN pro-adhesive phenotype and promotes PMN adhesion to cerebrovascular endothelial cells through a β2-integrin-ICAM-1-dependent mechanism. PMN adhesion to the brain microvasculature may contribute to SAE.

Inflammatory cytokines kinetics define the severity and phase of nephropathia epidemica

AIMS

Nephropathia epidemica (NE) is a form of hemorrhagic fever with renal syndrome associated with the Puumala virus species of Hantavirus. The pathogenesis of NE is not well understood; therefore, investigating the inflammatory cytokine response to infection may provide useful knowledge in deciphering the pathophysiology of NE.

MATERIALS & METHODS

Using Luminex and ELISA, we analyzed the serum of 137 NE cases and 44 controls to investigate if serum cytokines associate with different clinical presentations.

RESULTS

Serum levels of TNF-α and IL-1β are associated with disease severity while upregulation of IL-6, CXCL10, CCL2 and CCL3 are associated with clinical presentation.

CONCLUSION

Inflammatory cytokine kinetics associate with the severity and phase of NE. Our data support a role for inflammatory cytokines in the pathophysiology of NE.

Comparative impact of antiretroviral drugs on markers of inflammation and immune activation during the first two years of effective therapy for HIV-1 infection: an observational study

Background

Few studies have compared the impact of different antiretroviral regimens on residual immune activation and inflammation with discordant results. Aim of the study was to investigate the impact of various antiretroviral regimens on markers of immune activation and inflammation during the first two years of effective therapy.

Methods

We studied HIV-infected antiretroviral-naïve patients who began cART with either abacavir/lamivudine or tenofovir/emtricitabine, combined with ritonavir-boosted lopinavir (LPV/r), atazanavir (ATV/r) or efavirenz (EFV). All the patients had a virological response within 6 months, which was maintained for 2 years with no change in their ART regimen. C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble CD14 (sCD14), monokine induced by interferon-γ (MIG) and interferon-γ-inducible protein-10 (IP-10) were measured in stored plasma obtained at cART initiation and 24 months later. Mean changes from baseline were analyzed on log_e-transformed values and multivariable linear regression models were used to study the effect of the treatment components, after adjusting for factors that might have influenced the choice of ART regimen or biomarker levels. Differences were expressed as the mean fold change percentage difference (Δ).

Results

Seventy-eight patients (91% males) with a median age of 43 years met the inclusion criteria. Their median baseline CD4 cell count was 315/mm³ and HIV-1 RNA level 4.6 log₁₀ copies/ml. During the 2-years study period, IL-6, IP-10 and MIG levels fell significantly, while hs-CRP and sCD14 levels remained stable. IP-10 and MIG levels declined significantly less strongly with ATV/r than with EFV (IP-10Δ -57%, p = 0.011; MIGΔ -136%, p = 0.007), while no difference was noted between LPV/r and EFV. The decline in IL-6 did not differ significantly across the different treatment components.

Conclusions

After the first 2 years of successful cART, IL-6, IP-10 and MIG fell markedly while hs-CRP and sCD14 levels remained stable. The only impact of ART regimen was a smaller fall in markers of immune activation with ATV/r than with EFV. Our results suggest that these markers could be worthwhile when evaluating new antiretroviral drugs.

Inhibition of angiogenesis, fibrosis and thrombosis by tetramethylpyrazine: mechanisms contributing to the SDF-1/CXCR4 axis

BACKGROUND

Tetramethylpyrazine (TMP) is one of the active ingredients extracted from the Chinese herb Chuanxiong, which has been used to treat cerebrovascular and cardiovascular diseases, pulmonary diseases and cancer. However, the molecular mechanisms underlying the actions of TMP have not been fully elucidated. In a previous study we showed that TMP-mediated glioma suppression and neural protection involves the inhibition of CXCR4 expression. The SDF-1/CXCR4 axis plays a fundamental role in many physiological and pathological processes. In this study, we further investigated whether the regulation of the SDF-1/CXCR4 pathway is also involved in the TMP-mediated inhibition of neovascularization or fibrosis and improvement of microcirculation.

METHODOLOGY/PRINCIPAL FINDINGS

Using a scratch-wound assay, we demonstrated that TMP significantly suppressed the migration and tubule formation of the human umbilical vein endothelial cell line ECV304 in vitro. The expression of CXCR4 in ECV304 cells is notably down-regulated after TMP treatment. In addition, TMP significantly suppresses corneal neovascularization in a rat model of corneal alkali burn injury. The expression of CXCR4 on days 1, 3 and 7 post-injury was determined through RT-PCR analysis. Consistent with our hypotheses, the expression of CXCR4 in the rat cornea is significantly increased with alkali burn and dramatically down-regulated with TMP treatment. Moreover, TMP treatment significantly attenuates bleomycin-induced rat pulmonary fibrosis, while immunofluorescence shows a notably decreased amount of CXCR4-positive cells in the TMP-treated group. Furthermore, TMP significantly down-regulates the expression of CXCR4 in platelets, lymphocytes and red blood cells. Whole-blood viscosity and platelet aggregation in rats are significantly decreased by TMP treatment.

CONCLUSIONS

These results show that TMP exerts potent effects in inhibiting neovascularization, fibrosis and thrombosis under pathological conditions; thus, the underlying mechanism of TMP might partially contribute to the down-regulation of CXCR4.

Clone clusters in autoreactive CD4 T-cell lines from probable multiple sclerosis patients form disease-characteristic signatures

We developed a method for selectively propagating disease-related autoreactive T-cell lines (auTCLs) based on their increased resistance to apoptosis. The generated auTCLs homogeneously co-express CD45RO and CD49a, adhere strongly to extracellular matrix proteins and express high interleukin-17 (IL-17) messenger RNA levels, resembling a T-cell subset proposed to transmigrate into tissues and induce systemic and local inflammation in rheumatoid arthritis. The combinations of T-cell oligoclones that comprise probable multiple sclerosis (pMS) disease-related lines use a unique portfolio of T-cell receptor beta-chain variable allele (BV genes) combinations forming 'disease-specific cluster patterns'. The auTCL derived from different patients and from different myelin epitopes display striking similarities in BV gene allele clusters and are derived primarily from a disease-prone hotspot residing in the BV gene locus between Vbeta6 and Vbeta9. Conversely, healthy subject TCLs use different BV gene allele sets, forming 'healthy responder usage formats'. These formats were absent from the pMS patient V-beta gene allele combinations evaluated in this study. Hierarchical clustering of the BV gene combinations, distinguish three pMS auTCL groups, implying existence of up to three disease-related immune response patterns. These subgroup patterns may reflect different disease subclasses or alternatively they may suggest immune reactivity to different aetiological agents. Analyses of clonal-clustering patterns may potentially aid in subclassification of MS or in characterizing aetiological agents of this disease.

Elevated CXCL12 expression in the bone marrow of NOD mice is associated with altered T cell and stem cell trafficking and diabetes development

Background

Type I diabetes (TID) is an autoimmune disease resulting from destruction of the insulin-producing β-cells by autoreactive T cells. Studies have shown that polymorphisms of chemokine CXCL12 gene are linked to TID in humans. In non-obese diabetic (NOD) mice, which are predisposed to develop the disease, reduction of CXCL12 level leads to significant delays in the onset of diabetes. Despite these initial observations, however, how CXCL12 affects development of TID has not been fully investigated.

Results

We found that the level of CXCL12 transcript is significantly elevated in the bone marrow of NOD mice as compared to Balb/c and C57BL/6 mice. Correspondingly, naïve T cells, regulatory T cells and hematopoietic stem cells (HSC) accumulate in the bone marrow of NOD mice. Treatment of NOD mice with AMD3100, an antagonist for CXCL12's receptor CXCR4, mobilizes T cells and HSC from the bone marrow to the periphery, concomitantly inhibits insulitis and delays the onset of diabetes.

Conclusion

These results suggest that the elevated CXCL12 expression promotes TID in NOD mice by altering T cell and hematopoietic stem cell trafficking. The findings highlight the potential usefulness of AMD3100 to treat or prevent TID in humans.

Unaltered graft survival and intragraft lymphocytes infiltration in the cardiac allograft of Cxcr3-/- mouse recipients

Previous studies showed that absence of chemokine receptor Cxcr3 or its blockade prolong mouse cardiac allograft survival. We evaluated the effect of the CXCR3 receptor antagonist MRL-957 on cardiac allograft survival, and also examined the impact of anti-CXCR3 mAb in human CXCR3 knock-in mice. We found only a moderate increase in graft survival (10.5 and 16.6 days, p < 0.05) using either the antagonist or the antibody, respectively, compared to control (8.7 days). We re-evaluated cardiac allograft survival with two different lines of Cxcr3(-/-) mice. Interestingly, in our hands, neither of the independently derived Cxcr3(-/-) lines showed remarkable prolongation, with mean graft survival of 9.5 and 10.8 days, respectively. There was no difference in the number of infiltrating mononuclear cells, expansion of splenic T cells or IFN-gamma production of alloreactive T cells. Mechanistically, an increased other chemokine receptor fraction in the graft infiltrating CD8 T cells in Cxcr3(-/-) recipients compared to wild-type recipients suggested compensatory T-cell trafficking in the absence of Cxcr3. We conclude Cxcr3 may contribute to, but does not govern, leukocyte trafficking in this transplant model.

Antibody microarray analysis of cell surface antigens on CD4+ and CD8+ T cells from HIV+ individuals correlates with disease stages

Background

Expression levels of cell surface antigens such as CD38 and HLA-DR are related to HIV disease stages. To date, the immunophenotyping of cell surface antigens relies on flow cytometry, allowing estimation of 3–6 markers at a time. The recently described DotScan antibody microarray technology enables the simultaneous analysis of a large number of cell surface antigens. This new technology provides new opportunities to identify novel differential markers expressed or co-expressed on CD4+ and CD8+ T cells, which could aid in defining the stage of evolution of HIV infection and the immune status of the patient.

Results

Using this new technology, we compared cell surface antigen expression on purified CD4+ and CD8+ T cells between 3 HIV disease groups (long-term non-progressors controlling viremia naturally; HIV+ patients on highly active antiretroviral therapy (HAART) with HIV plasma viral loads <50 copies/ml; and HIV+ patients with viremia during HAART) and uninfected controls. Pairwise comparisons identified 17 statistically differential cell surface antigens including 5 novel ones (CD212b1, CD218a, CD183, CD3 epsilon and CD9), not previously reported. Notably, changes in activation marker expression were more pronounced in CD8+ T cells, whereas changes in the expression of cell membrane receptors for cytokines and chemokines were more pronounced in CD4+ T cells.

Conclusion

Our study not only confirmed cell surface antigens previously reported to be related to HIV disease stages, but also identified 5 novel ones. Of these five, three markers point to major changes in responsiveness to certain cytokines, which are involved in Th1 responses. For the first time our study shows how density of cell surface antigens could be efficiently exploited in an array manner in relation to HIV disease stages. This new platform of identifying disease markers can be further extended to study other diseases.

In vitro reconstitution and preparative purification of complexes between the chemokine receptor CXCR4 and its ligands SDF-1alpha, gp120-CD4 and AMD3100

CXCR4 belongs to the family of G protein-coupled receptors and mediates the various developmental and regulatory effects of the chemokine SDF-1alpha. In addition, CXCR4 acts as a co-receptor along with CD4 for the HIV-1 viral glycoprotein gp120. Recently, there has also been a small molecule described that antagonizes both SDF-1 and gp120 binding to CXCR4. The structural and mechanistic basis for this dual recognition ability of CXCR4 is unknown largely due to the technical challenges of biochemically producing the components of the various complexes. We expressed the human CXCR4 receptor using a modified baculovirus expression vector that facilitates a single step antibody affinity purification of CXCR4 to >80% purity from Hi5 cells. The recombinant receptor undergoes N-linked glycosylation, tyrosine sulfation and is recognized by the 12G5 conformation specific antibody against human CXCR4. We are able to purify CXCR4 alone as well as complexed with its endogenous ligand SDF-1, its viral ligand gp120, and a small molecule antagonist AMD3100 by ion-exchange chromatography. We anticipate that the expression and purification scheme described in this paper will facilitate structure-function studies aimed at elucidating the molecular basis for CXCR4 recognition of its endogenous chemokine and viral ligands.

A sulfated disaccharide derived from chondroitin sulfate proteoglycan protects against inflammation-associated neurodegeneration

Chondroitin sulfate proteoglycan (CSPG), a matrix protein that occurs naturally in the central nervous system (CNS), is considered to be a major inhibitor of axonal regeneration and is known to participate in activation of the inflammatory response. The degradation of CSPG by a specific enzyme, chondroitinase ABC, promotes repair. We postulated that a disaccharidic degradation product of this glycoprotein (CSPG-DS), generated following such degradation, participates in the modulation of the inflammatory responses and can, therefore, promote recovery in immune-induced neuropathologies of the CNS, such as experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune uveitis (EAU). In these pathologies, the dramatic increase in T cells infiltrating the CNS is far in excess of the numbers needed for regular maintenance. Here, we show that CSPG-DS markedly alleviated the clinical symptoms of EAE and protected against the neuronal loss in EAU. The last effect was associated with a reduction in the numbers of infiltrating T cells and marked microglia activation. This is further supported by our in vitro results indicating that CSPG-DS attenuated T cell motility and decreased secretion of the cytokines interferon-gamma and tumor necrosis factor-alpha. Mechanistically, these effects are associated with an increase in SOCS-3 levels and a decrease in NF-kappaB. Our results point to a potential therapeutic modality, in which a compound derived from an endogenous CNS-resident molecule, known for its destructive role in CNS recovery, might be helpful in overcoming inflammation-induced neurodegenerative conditions.

CD24 affects CXCR4 function in pre-B lymphocytes and breast carcinoma cells

CD24 is a small, heavily glycosylated cell-surface protein which is linked to the membrane via a glycosyl-phosphatidylinositol (GPI-) anchor and therefore localizes in lipid rafts. CD24 is widely used as a cell-lineage marker for hematopoietic cells. CD24 is also expressed on a variety of human carcinomas, including epithelial ovarian, breast, prostate, colon and lung cancer and has been linked to poor prognosis. Except for its role as a ligand for P-selectin on carcinoma and myeloid cells, a specific function for CD24 has not been determined. Here we show that CD24 affects the function of the chemokine receptor CXCR4. Using isolated CD19-positive bone marrow B cells from CD24-knockout mice and CD24-/- pre-B lymphocytic cell lines, we demonstrate that CD24 expression reduces SDF-1-mediated cell migration and signalling via CXCR4. We observed that the loss of CD24 augmented cellular cholesterol levels and enhanced CXCR4 lipid raft association. Altered chemotactic migration and raft residence was also observed in MDA-MB-231 breast cancer cells expressing high and low levels of CD24 and CXCR4 receptor. MDA-MB-231 cells expressing low levels of CD24 also showed enhanced tumour formation in NOD/SCID mice compared with cells overexpressing CD24. These results demonstrate a novel role for CD24 as a regulator of CXCR4 function that could be relevant for breast cancer growth and metastasis.

Pitavastatin-induced downregulation of CCR2 and CCR5 in monocytes is associated with the arrest of cell-cycle in S phase

The pleiotropic effects of statin, including its anti-inflammatory effects, via chemokines may be independent of statin-induced cholesterol reduction. Therefore, we examined the effect of pitavastatin on cell proliferation and the association between chemokine receptors (CCR2 and CCR5) and their ligands, RANTES (regulated upon activation, normal T cell-expressed and secreted) and monocyte chemotactic protein-1 (MCP-1), in monocytes. Pitavastatin but not pravastatin inhibited cell proliferation in a dose-dependent manner and showed S-phase arrest associated with the downregulation of CCR2 and CCR5 expression in human monocytic tumor cells (U937 cells). Although the anti-proliferative effects of pitavastatin were not inhibited by lower concentrations of RANTES and MCP-1, overexpression of CCR2/CCR5 significantly blocked the anti-proliferation with a low concentration of RANTES or MCP-1. Pitavastatin upregulated p21(waf1) but not p27(kip1), and did not change the expression levels of cyclin D1 or cdk4. In addition, RANTES and MCP-1 upregulated cyclin D1 in the presence of pitavastatin. In conclusion, the anti-proliferative effect of pitavastatin, but not pravastatin, through the downregulation of CCR2/CCR5 may be a pleiotropic effect. This effect may be anti-atherogenic in monocytes.

Gene expression profiling of minor salivary glands clearly distinguishes primary Sjögren's syndrome patients from healthy control subjects

OBJECTIVE

To identify gene expression signatures in minor salivary glands (MSGs) from patients with primary Sjogren's syndrome (SS).

METHODS

A 16K complementary DNA microarray was used to generate gene expression profiles in MSGs obtained from 10 patients with primary SS and 10 control subjects. The data were analyzed by 2 different strategies, one strict primary analysis and one subanalysis that allowed for inclusion of genes with no signal in more than 3 samples from each group. The results were validated by quantitative reverse transcriptase-polymerase chain reaction techniques.

RESULTS

We found a distinct difference in gene expression levels in MSGs, enabling a simple class prediction method to correctly classify 19 of the 20 samples as either patient or control, based on the top 5 differentially expressed genes. The 50 most differentially expressed genes in the primary SS group compared with the control group were all up-regulated, and a clear pattern of genes involved in chronic inflammation was found. CXCL13 and CD3D were expressed in >/=90% of primary SS patients and in </=10% of the controls. Lymphotoxin beta, as well as a number of major histocompatibility complex genes, cytokines, and lymphocyte activation factors, manifested its role in the pathogenesis of SS. Numerous type I interferon genes related to virus infection were found among the top 200 genes, with increased expression in primary SS. Interestingly, the expression of carbonic anhydrase II, which is essential in saliva production and secretion, and the apoptosis regulator Bcl-2-like 2 were down-regulated in primary SS patients.

CONCLUSION

We have identified distinct gene expression profiles in MSGs from patients with primary SS that provide new knowledge about groups of genes that are up-regulated or down-regulated during disease, constituting an excellent platform for forthcoming functional studies.

Chemokines: role in inflammation and immune surveillance

Chemotactic migration of leucocytes largely depends on adhesive interaction with the substratum and recognition of a chemoattractant gradient. Both aspects, cell adhesion and chemotaxis, are regulated by members of the family of chemotactic cytokines (chemokines) comprising structurally related and secreted proteins of 67-127 amino acids in length. Breakdown in the control of leucocyte mobilisation contributes to chronic inflammatory diseases and, hence, interference with chemokine function is a promising approach for the development of novel anti-inflammatory medication. Chemokines target all types of leucocyte, including haematopoietic precursors, mature leucocytes of the innate immune system as well as naive, memory, and effector lymphocytes. The combinatorial diversity in responsiveness to chemokines ensures proper tissue distribution of distinct leucocyte subsets under normal and inflammatory/pathological conditions. Here, we discuss recent views on the role of chemokines in controlling tissue localisation of human memory T cells under steady state (non-inflamed) conditions. Emphasis is placed on a concept describing distinct subsets of memory T cells according to their primary residence in peripheral blood, secondary lymphoid tissues, or peripheral (extralymphoid) tissues.

IFN-gamma-inducible chemokines enhance adaptive immunity and colitis

T helper type 1 (Th1) cells secreting interferon-gamma (IFN-gamma) have been closely associated with Crohn's disease (CD). Monokine-induced by IFN-gamma (MIG), IFN-gamma-inducible T cell alpha chemoattractant (I-TAC), and IFN-gamma-inducible protein-10 (IP-10), are chemokines that bind CXCR3 and mediate the chemotaxis of leukocytes. IP-10, MIG, and CXCR3 have been shown to be expressed at sites of CD. The current study stems from our recent findings that IP-10, MIG, and I-TAC significantly contribute to the development of Th1-mediated inflammatory responses. To better understand the role of CXCR3 interactions during CD, we characterized the effects of IP-10, MIG, I-TAC, and CXCR3+ T cells on mucosal immune responses. IP-10, MIG, and I-TAC significantly enhanced antigen-specific serum and mucosal antibodies through Th1-mediated events and CD28 modulation. Additionally, the adoptive transfer of naive CXCR3+ T cells and CD4+CD45RB(HI) to T cell receptor beta (TCRbeta) x delta(-/-) mice resulted in the onset of murine colitis. Taken together, these studies suggest that IP-10, MIG, I-TAC, and CXCR3 interactions are involved in mucosal immune responses required for the induction of CD.

Allicin inhibits SDF-1alpha-induced T cell interactions with fibronectin and endothelial cells by down-regulating cytoskeleton rearrangement, Pyk-2 phosphorylation and VLA-4 expression

Allicin, a major ingredient of fresh garlic extract that is produced during the crushing of garlic cloves, exerts various beneficial biological effects, including a broad spectrum of antimicrobial activity, antihyperlipidaemic and antihypertensive effects. However, how allicin affects the immune system is less well known, and its effect on human T cells has never been studied. Here, we examined the in-vitro effects of allicin on the functioning of T cells related to their entry to inflamed extravascular sites. We found that allicin (20-100 microm) inhibits the SDF-1alpha (CXCL12)-induced T cell migration through fibronectin (FN), and that this inhibition is mediated by the down-regulation of (i) the reorganization of cortical actin and the subsequent T cell polarization, and (ii) T cell adhesion to FN. Moreover, allicin also inhibited T cell adhesion to endothelial cells and transendothelial migration. The mechanisms underlying these inhibitory effects of allicin are associated with its ability to down-regulate the phosphorylation of Pyk2, an intracellular member of the focal adhesion kinases, and to reduce the expression of the VCAM-1- and FN-specific alpha4beta1-integrin (VLA-4). The ability of allicin to down-regulate these chemokine-induced and VLA-4-mediated T cell functions explains its beneficial biological effects in processes where T cells play an important role and suggests that allicin may be used therapeutically with chronic inflammatory diseases.

Functional expression of CXCR4 (CD184) on small-cell lung cancer cells mediates migration, integrin activation, and adhesion to stromal cells

Small-cell lung cancer (SCLC) is an aggressive, rapidly metastasizing neoplasm. The chemokine stromal cell-derived factor-1 (SDF-1/CXCL12) is constitutively secreted by marrow stromal cells and plays a key role for homing of hematopoietic cells to the marrow. Here, we report that tumor cells from patients with SCLC express high levels of functional CXCR4 receptors for the chemokine CXCL12. Reverse transcriptase-polymerase chain reaction and flow cytometry demonstrated CXCR4 mRNA and CXCR4 surface expression in SCLC cell lines. Immunohistochemistry of primary tumor samples from SCLC patients revealed high expression of CXCR4. CXCL12 elicited CXCR4 receptor endocytosis, actin polymerization, and a robust activation of phospho-p44/42 mitogen-activated protein kinase in SCLC cells. Furthermore, CXCL12 induced SCLC cell invasion into extracellular matrix and firm adhesion to marrow stromal cells. Stromal cell adhesion of SCLC cells was significantly inhibited by the specific CXCR4 antagonist T140, pertussis toxin, antivascular cell adhesion molecule-1(VCAM-1) antibodies, and CS-1 peptide, demonstrating the importance of CXCR4 chemokine receptor activation and alpha4beta1 integrin binding, respectively. In addition, CXCL12 enhanced the adhesion of SCLC cells to immobilized VCAM-1, demonstrating that CXCR4 chemokine receptors can induce integrin activation on SCLC cells. As SCLC has a high propensity for bone marrow involvement, our findings suggest that CXCR4 chemokine receptors and alpha4beta1 integrins play a critical role in the interaction of SCLC cells with stromal cells in the tumor microenvironment.

Expression analysis of the T-cell-targeting chemokines CXCL9 and CXCL10 in mice and humans with endothelial infections caused by rickettsiae of the spotted fever group

Rocky Mountain spotted fever and other related diseases are systemic infections caused by rickettsiae. These obligatory intracellular bacteria target the endothelium, offering an appealing model to study the interactions between endothelial cells and T lymphocytes. We investigated the mRNA expression of chemokines known to target CD8+ T cells and CD4(+) T-helper 1 cells in the lungs of C3H/HeN mice infected with Rickettsia conorii with the purpose of identifying evidence for a role of chemokines in the immune clearance of rickettsiae from the vasculature. The expression of the CXCR3 ligands CXCL9 and CXCL10 was significantly higher than the other chemokines investigated. We validated the relevance of these results in the animal model through the analysis of tissues from humans with Rocky Mountain spotted fever. We then characterized the kinetics and localization of expression of CXCL9 and CXCL10 in lungs, brain, and liver of mice infected with lethal or sublethal doses of R. conorii by a combination of quantitative real-time polymerase chain reaction and immunohistochemistry. Interestingly, the peak of expression of these chemokines occurred 4 days before CD8+ T cells infiltrated the infected tissues. Our results suggest that CXCL9 and CXCL10 may play a role early during the immune response against rickettsial infections.

Evidence of CXC, CC and C chemokine production by lymphatic endothelial cells

Although production of chemokines by vascular endothelial cells has been documented, there is only limited information regarding the expression of chemokines by the lymphatic endothelium. Here we used lymphatic endothelial cells (LEC) derived from experimentally induced murine lymphangiomas to investigate the pattern of chemokine expression by these cells. Histological analysis of the lymphatic hyperplasia revealed the presence of leucocytes in the tissues surrounding the lesions, suggesting the presence of chemoattractant activity. A functional chemotactic assay on human polymorphonuclear cells and on purified subpopulations of murine leucocytes using culture supernatants from LEC primary cultures confirmed the presence of chemoattractant activity. The identity of different cytokines of the CXC, CC and C subfamilies was investigated by reverse trancriptase-polymerase chain reaction on total endothelial cell RNA. Amplified fragments corresponding to KC, IP10, Mig-1, BCL, MIP-2, SLC, RANTES, MCP-1, C10, and Lptn were obtained, and confirmed by Southern blot and sequencing. In contrast, MIP-1alpha, MIP-1beta, and MIP-1gamma were not detected. Higher levels of expression were revealed by Northern blot analysis for Mig-1, MCP-1 and C10. The lymphatic endothelium-restricted production of these chemokines was also confirmed by in situ hybridization. The presence of high C10 mRNA expression levels in LEC was particularly unexpected, because the production of this molecule has been previously identified only in cells of the haematopoietic lineage. These observations represent the first detailed analysis of chemokine production by lymphatic endothelial cells and may account, in part, for the mechanism of leucocyte recruitment into the lymphatics, and of lymphocyte recirculation within the lymphatic system.

Involvement of the interferon-gamma-induced T cell-attracting chemokines, interferon-gamma-inducible 10-kd protein (CXCL10) and monokine induced by interferon-gamma (CXCL9), in the salivary gland lesions of patients with Sjögren's syndrome

OBJECTIVE

To elucidate the mechanism of the development of T cell infiltrates in the salivary glands of patients with Sjögren's syndrome (SS), we studied T cell-attracting chemokines and their receptors.

METHODS

The expression of the T cell-attracting chemokines, interferon-gamma (IFNgamma)-inducible 10-kd protein (IP-10; also called CXCL10), monokine induced by IFNgamma (Mig; also called CXCL9), and stromal cell-derived factor 1 (SDF-1; also called CXCL12), in salivary glands from SS patients was investigated by polymerase chain reaction-enzyme-linked immunosorbent assay (ELISA). Cells that produce chemokines and lymphocytes that express chemokine receptors were identified by immunohistochemistry. The production of IP-10 and Mig proteins by salivary epithelial cells in response to IFNgamma was determined by ELISA.

RESULTS

Expression of IP-10 and Mig messenger RNA (mRNA) was significantly up-regulated in SS salivary glands compared with normal salivary glands (both P < 0.01). There was no significant difference in SDF-1 mRNA expression between the SS and normal salivary glands. IP-10 and Mig proteins were predominantly expressed in the ductal epithelium adjacent to lymphoid infiltrates. Most of the CD3+ infiltrating lymphocytes in dense periductal foci expressed CXCR3, the receptor for IP-10 and Mig. IFNgamma induced the production of high levels of IP-10 and Mig proteins from cultured SS salivary epithelial cells.

CONCLUSION

These findings suggest that IFNgamma stimulates the production of IP-10 and Mig in the SS ductal epithelium, and that IP-10 and Mig are involved in the accumulation of T cell infiltrates in the SS salivary gland. Chemokines or chemokine receptors could be a rational new therapeutic target in SS.

Detection of alloreactive T cells by flow cytometry: a new test compared with limiting dilution assay

BACKGROUND

Frequencies of alloreactive T cells determined by limiting dilution assays (LDA) may not adequately reflect the donor-reactive immune status in transplant recipients. To reevaluate LDA frequencies, we developed a flow cytometry test for direct determination of alloreactive T-cell frequencies and compared these frequencies with classical LDA estimates of frequencies.

METHODS

For determination of frequencies by flow cytometry, peripheral blood lymphocytes (or lymphocytes taken from primary mixed lymphocyte culture) were stimulated with either Epstein-Barr virus-transformed lymphoblastoid cell lines or T cell-depleted spleen cells and stained for intracellular interferon (IFN)-gamma production and CD69. In lung transplant recipients, frequencies of IFN+ alloreactive T cells were compared with LDA frequencies, that is, cytotoxic T lymphocyte precursors and helper T lymphocyte precursors.

RESULTS

With flow cytometry, alloreactive T cells were detected after overnight allostimulation as IFN-gamma CD69bright cells (range, 0.1-0.58% and 0.1-0.66% of total CD4 and CD8 cells, respectively). Frequencies increased 25-fold or more when lymphocytes were prestimulated in primary mixed lymphocyte culture before testing. After lung transplantation, mean donor-specific IFN+ CD8 T-cell frequencies did not decrease as mean donor-specific LDA cytotoxic T lymphocyte precursor frequencies, whereas no difference was seen in pretransplantation samples or third-party-specific frequencies at both time points. Mean frequencies of IFN+ CD4 did not differ from helper T lymphocyte precursors at both time points, but frequencies did not correlate.

CONCLUSIONS

The flow cytometry test allows a direct measurement of alloreactive T-cell frequencies and demonstrates a discrepancy between donor-specific IFN+ CD8 T-cell frequencies and LDA CLTp after transplantation. This may be a result of the existence of "functional diverse" alloreactive T cells or of activation-induced cell death of donor-reactive T cells during long (LDA) culturing, which is avoided in the flow cytometry test.

AMD3100, a CxCR4 antagonist, attenuates allergic lung inflammation and airway hyperreactivity

The role of specific chemokine receptors during allergic asthmatic responses has been relatively undefined. A number of receptors are preferentially expressed on Th2 cells, including CCR4, CCR8, and CxCR4. In the present study, we have examined the role of CxCR4 in the development of cockroach allergen-induced inflammation and airway hyperreactivity in a mouse model of asthma. Using a specific inhibitor of CxCR4, AMD3100, our results indicate that blocking this receptor has a significant effect in down-regulating the inflammation and pathophysiology of the allergen-induced response. Treatment of allergic mice with AMD3100 significantly reduced airway hyperreactivity, peribronchial eosinophilia, and the overall inflammatory responses. In addition, there was a shift in the cytokine profile that was observed in the AMD3100-treated animals. Specifically, there was a significant reduction in interleukin-4 and interleukin-5 levels and a significant increase in interleukin-12 and interferon-gamma levels within the lungs of treated allergic mice. Furthermore, there was a significant alteration in the local chemokine production of CCL22 (MDC) and CCL17 (TARC), two chemokines previously shown to be important in Th2-type allergen responses. Overall, specifically blocking CxCR4 using AMD3100 reduced a number of pathological parameters related to asthmatic-type inflammation.

Interaction with glycosaminoglycans is required for cyclophilin B to trigger integrin-mediated adhesion of peripheral blood T lymphocytes to extracellular matrix

Cyclophilins A and B (CyPA and CyPB) are cyclosporin A-binding proteins that are involved in inflammatory events. We have reported that CyPB interacts with two types of cell-surface-binding sites. The first site corresponds to a functional receptor and requires interaction with the central core of CyPB. This region is highly conserved in cyclophilins, suggesting that CyPA and CyPB might share biological activities mediated by interaction with this receptor. The second site is identified with glycosaminoglycans (GAGs), the binding region located in the N terminus of CyPB. The difference in the N-terminal extensions of CyPA and CyPB suggests that a unique interaction with GAGs might account for selective activity of CyPB. To explore this hypothesis, we analyzed the lymphocyte responses triggered by CyPA, CyPB, and CyPB(KKK-), a mutant unable to interact with GAGs. The three ligands seemed capable enough to elicit calcium signal and chemotaxis by binding to the same signaling receptor. In contrast, only CyPB enhanced firm adhesion of T cells to the extracellular matrix. This activity depended on the interactions with GAGs and signaling receptor. CyPB-mediated adhesion required CD147 presumably because it was a costimulatory molecule and was related to an activation of alpha4beta1 and alpha4beta7 integrins. Finally, we showed that CyPB was capable mainly to enhance T cell adhesion of the CD4+CD45RO+ subset. The present data indicate that CyPB rather than CyPA is a proinflammatory factor for T lymphocytes and highlight the crucial role of CyPB-GAG interaction in the chemokine-like activity of this protein.

In vivo functions of heterotrimeric G-proteins: studies in Galpha-deficient mice

Heterotrimeric guanine nucleotide binding proteins (G-proteins) mediate the effects of numerous hormones, neurotransmitters or sensory stimuli by coupling their transmembranous receptors to various effectors like enzymes and ion channels. Changes in the activity of these effector molecules eventually lead to the regulation of multiple cellular functions ranging from short term regulatory processes like the control of secretion rates, muscle tonus or metabolic processes to long term effects like regulation of growth and differentiation. Heterotrimeric G-proteins play a pivotal role in this transmembrane signaling process as they take part in processing and sorting of incoming signals as well as in adjusting the sensitivity of the system. This review describes some of the new insights into the biological role of G-protein mediated signaling processes provided by the analysis of mice genetically engineered to lack distinct G-protein alpha-subunits.

Chemokines and viral diseases of the central nervous system

This chapter discusses chemokines and their receptors in the evolution of viral infectious diseases of the central nervous system (CNS). Infection of the human CNS with many different viruses or infection of the rodent CNS induces vigorous host-inflammatory responses with recruitment of large numbers of leukocytes, particularly T lymphocytes and macrophages. Chemokines coordinate trafficking of peripheral blood leukocytes by stimulating their chemotaxis, adhesion, extravasation, and other effector functions. In view of these properties, research efforts have turned increasingly to the possible involvement of chemokines in regulating both peripheral tissue and CNS leukocyte migration during viral infection. The biological effects of chemokines are mediated via their interaction with receptors belonging to the family of seven transmembrane (7TM)-spanning, G-protein coupled receptors (GPCRs). In the normal mammalian CNS, the number of leukocytes present in the brain is scant. However, these cells are attracted to, and accumulate in, a variety of pathologic states, many involving viral infection. Although leukocyte migration into local tissue compartments, such as the CNS, is a multifactorial process, it has become clear that chemokines are pivotal components of this process, providing a necessary chemotactic signal for leukocyte recruitment.

CpG motifs of DNA vaccines induce the expression of chemokines and MHC class II molecules on myocytes

Determining how an immune response is initiated after in vivo transfection of myocytes with plasmids encoding foreign antigens is essential to understand the mechanisms of intramuscular (i. m.) genetic immunization. Since myocytes are facultative antigen-presenting cells lacking MHC class II and co-stimulatory molecules, it was assumed that their unique role upon DNA vaccination is to synthesize and secrete the protein encoded by the plasmid. Here we describe that i. m. injection of unmethylated CpG motifs induced the expression of chemokines (monocyte chemotactic protein-1) and MHC class II molecules on myocytes. Our results indicate that immunostimulatory DNA sequences (CpG motifs) of DNA vaccines augment synthesis of chemokine by myocytes with subsequent recruitment of inflammatory cells secreting IFN-gamma, a potent cytokine that up-regulates the expression of MHC class II molecules on myocytes. A myoblast cell line triple transfected with plasmids encoding MHC class II molecules and an immunodominant CD4 T cell epitope of influenza virus presented the endogenously synthesized peptide and activated specific T cells. These findings suggest that one mechanism for the immunogenicity of DNA vaccines consists in the presentation of peptides to CD4 T cells by in vivo plasmid-transfected myocytes.

Migration of helper T-lymphocyte subsets into inflamed tissues

The localization of lymphocytes to specific tissues is a finely regulated event that has key implications in the development of chronic allergic inflammation that is associated with allergic rhinitis, atopic dermatitis, and asthma. Key players in the tissue localization of lymphocytes and other allergic effector cells include cellular adhesion molecules and chemokines. The expression or activation pattern of these proinflammatory mediators appears to depend, in part, on the local cytokine milieu. For instance, the T(H)1 phenotype is associated with the upregulation of intercellular adhesion molecule-1 and RANTES, whereas the T(H)2 phenotype is associated with the upregulation of vascular cell adhesion molecule and P-selectin. Notably, the recruitment of certain cell populations, such as eosinophils (hallmark of chronic allergic inflammation), into inflamed tissue sites is dependent on the preferential expression of adhesion molecules, chemokines, and associated receptors. The potential mechanisms that underlie cell migration into inflamed tissue as currently understood are reviewed.

Exposure to UVB induces accumulation of LFA-1+ T cells and enhanced expression of the chemokine psoriasin in normal human skin

Normal human skin shows preferential (epi)dermal infiltration of CD4+ T cells upon acute UV exposure. To study the mechanism behind this feature we locally exposed healthy volunteers to doses of UV commonly encountered by the population. Expression of integrins on T cells and expression of adhesion molecules on dermal endothelial cells were quantitatively assessed by immunohistochemistry in situ. We also investigated the effects of ultraviolet-B (UVB) exposure on psoriasin and IL-16, two specific chemoattractant factors for CD4+ T cells, at messenger RNA (mRNA) level by semiquantitative reverse transcriptase-polymerase chain reaction and at protein level by immunohistochemistry. We found, at day 2 after exposure to four minimal erythema doses of UVB, predominant accumulation of LFA-1+/CLA-/VLA-4- T cells in the dermis. Concomitantly the expression of ICAM-1, but not that of E-selectin and VCAM-1, was upregulated on dermal endothelial cells. The increase in the number of dermal T cells was not due to proliferation because only 2% of the UVB-induced dermal T cells expressed the marker of proliferation Ki-67. Whereas exposure to 35 J/cm2 of ultraviolet-A (UVA), like UVB, induced a loss of intraepidermal T cells at day 2 after exposure, UVA induced neither any influx of T cells into the dermis nor any adhesion molecule upregulation on endothelial cells. In response to UVB exposure, the expression of psoriasin mRNA, but not of IL-16 mRNA, was upregulated; the expression of psoriasin protein was also found to be upregulated. These results suggest that LFA-1/ICAM-1 pathway and psoriasin are both involved in the accumulation of CD4+ T cells into UVB-irradiated skin, possibly via a recruitment mechanism.

Signal transduction by CXC chemokine receptor 4. Stromal cell-derived factor 1 stimulates prolonged protein kinase B and extracellular signal-regulated kinase 2 activation in T lymphocytes

We report that stromal cell-derived factor (SDF)-1 has the remarkable capacity to induce sustained signaling through CXC chemokine receptor 4 (CXCR4). In contrast to other chemokines, such as monocyte chemotactic protein 1 (CC chemokine receptor 2 [CCR2]), macrophage inflammatory protein 1beta (CCR5), liver and activation-regulated chemokine (LARC [CCR6]), Epstein-Barr virus-induced molecule 1 ligand chemokine (ELC [CCR7]), and IP10 (CXCR3), SDF-1 stimulates the prolonged activation of protein kinase B and extracellular signal-regulated kinase (ERK)-2. Activation of protein kinase B is reversed by displacement of SDF-1 from CXCR4 or inhibition of phosphatidylinositol 3-kinase. Although increasing concentrations of SDF-1 enhance CXCR4 internalization, kinase activation is prolonged. In addition, restimulation yields >60% of initial protein kinase B activity, indicating that the remaining receptors are not desensitized. Furthermore, activation is prolonged by inhibiting SDF-1 degradation. The sustained activation of cell survival and mitogenic pathways may account for the unique role of SDF-1 and CXCR4 in embryogenesis and lymphopoiesis.

Solubilization of the chemokine receptor CXCR4

The chemokine receptor CXCR4 was solubilized from the human T-cell line CEM by using the detergent n-dodecyl-beta-maltoside (DDM) and cholesteryl hemisuccinate ester (CHS). Binding studies with (125)I-SDF-1alpha revealed a dissociation constant of 5.33 nM and a receptor density (B(max)) of 2.68 pmol/mg in CEM membranes at 4 degrees C. The affinity of solubilized CXCR4 for SDF-1alpha was identical to membrane-bound CXCR4. Binding of gp120 to solubilized CXCR4 was demonstrated by coprecipitation of gp120 with anti-CXCR4 antibodies.

Induction of interactions between CD44 and hyaluronic acid by a short exposure of human T cells to diverse pro-inflammatory mediators

Migration of T cells into extravascular sites of inflammation is mediated by cell-cell and cell-matrix adhesion receptors, including the hyaluronan-binding glycoprotein, CD44. The biochemical nature of CD44 variants and the ligand specificity, function and the regulation of activation of CD44 expressed on various cell types have been extensively studied. However, little is still known about the short-term influence of cytokines and chemokines on the activation of CD44 on human T cells. Therefore, we studied the role of inflammatory mediators in regulating the adhesion of T cells from human peripheral blood to immobilized hyaluronan under static or shear stress conditions. We found that the CD44-dependent adhesion, under static and shear stress (i.e. relative gradual resistance to flow of 150 and 1500 s-1) conditions, of T cells to hyaluronan requires a T-cell activation of 2-3 hr and is regulated by the cross-linking of CD3, cytokines (e.g. interleukin-2 and tumour necrosis factor-alpha), and chemokines (e.g. MIP-1beta, interleukin-8, and RANTES). This T-cell adhesion was manifested by polarization, spreading and co-localization of cell surface CD44 with a rearranged actin cytoskeleton in hyaluronan-bound T cells. Thus, cytokines and chemokines present in the vicinities of blood vessel walls or present intravascularly in tissues where immune reactions take place, can rapidly activate the CD44 molecules expressed on T cells.

Lymphocyte migration in the intestinal mucosa: entry, transit and emigration of lymphoid cells and the influence of antigen

Lymphocyte migration is important to transport immunological information between the different compartments of the intestinal immune system. Large numbers of lymphocytes emigrate from the Peyer's patches and reach the blood circulation after expansion and maturation within the mesenteric lymph nodes. So far the frequency of antigen specific lymphocytes emigrating from the Peyer's patches after oral stimulation is not known. After mesenteric lymph node resection those cells emigrating from the intestinal wall are accessible by calculating the major intestinal lymph duct. The first antigen specific cells draining from the intestines are obviously not lymphocytes but dendritic cells, thus the antigen is rapidly trapped in the parenchyma of the lymph nodes in vivo. When lymphocytes were taken from intestinal lymph, labeled in vitro and retransfused, marked numbers of B-cells were re-detected in intestinal lymph. Later preferentially T-cells recirculated through the gut wall. After immigration into the intestinal lamina propria the lymphocytes may enter the space between epithelial cells, where they are present as intraepithelial lymphocytes. Lymphoid cells in the S-phase of the cell cycle have been detected in all compartments of the intestinal wall. Apoptosis is probably a further important mechanism for the regulation of intestinal immunity in removing cells reacting against harmless dietary antigens to maintain oral tolerance.

Monocyte Chemoattractant Protein-1 Mediates Cockroach Allergen-Induced Bronchial Hyperreactivity in Normal But Not CCR2−/− Mice: The Role of Mast Cells

Bronchial eosinophil and mononuclear cell infiltrates are a hallmark of the asthmatic lung and are associated with the induction of reversible airway hyperreactivity. In these studies, we have found that monocyte chemotactic protein-1 (MCP-1), a CC (β) chemokine, mediates airway hyperreactivity in normal and allergic mice. Using a murine model of cockroach Ag-induced allergic airway inflammation, we have demonstrated that anti-MCP-1 Abs inhibit changes in airway resistance and attenuate histamine release into the bronchoalveolar lavage, suggesting a role for MCP-1 in mast cell degranulation. In normal mice, instillation of MCP-1 induced prolonged airway hyperreactivity and histamine release. In addition, MCP-1 directly induced pulmonary mast cell degranulation in vitro. These latter effects would appear to be selective because no changes were observed when macrophage-inflammatory protein-1α, eotaxin, or MCP-3 were instilled into the airways of normal mice or when mast cells were treated in vitro. Airway hyperreactivity was mediated by MCP-1 through CCR2 because allergen-induced as well as direct MCP-1 instilled-induced changes in airway hyperreactivity were significantly attenuated in CCR2 −/− mice. The neutralization of MCP-1 in allergic animals and instillation of MCP-1 in normal animals was related to leukotriene C4 levels in the bronchoalveolar lavage and was directly induced in pulmonary mast cells by MCP-1. Thus, these data identify MCP-1 and CCR2 as potentially important therapeutic targets for the treatment of hyperreactive airway disease.

Coexpression of CCR5 and IL-2 in Human Genital But Not Blood T Cells: Implications for the Ontogeny of the CCR5+ Th1 Phenotype

Memory T cells that home to inflamed tissues typically express the β-chemokine receptor CCR5 and exhibit a Th1 cytokine profile. The migration of these cells into the genital tract following antigenic exposure has particular relevance to acquisition of HIV-1 infection, because CCR5 functions as the coreceptor for most sexually transmitted HIV-1 strains. We recently established methodology to purify and culture mononuclear cells from the female reproductive tract, and here we analyzed the phenotype, CCR5 expression, and cytokine production of cervicovaginal T cells in up to 16 donors. The proportion of mucosal T cells expressing CCR5 was markedly expanded as compared with peripheral blood (mean 88% vs 24% in 13 donors), but the receptor density on individual CCR5+ T cells was only slightly increased (mean 5837 vs 4191 MEPE (molecules of equivalent PE) units in 6 of 7 donors). Intracellular costaining for IL-2, IFN-γ, IL-4, and IL-5 revealed a Th1-type pattern in cervical T cells, with significantly higher percentages of IL-2- and IFN-γ-producing T cells in the mucosa than in blood (mean 67% vs 29%). Coexpression of surface CCR5 with intracellular IL-2 and IFN-γ was observed only among T cells in the mucosa, but not among those in circulation. Thus, we postulate that T cell homing to the genital mucosa leads to differentiation into the combined CCR5+ Th1 phenotype. Moreover, the predominance of CCR5+ Th1-type T cells in normal cervical mucosa provides targets accessible for the efficient transmission of macrophage-tropic HIV-1 variants in women following sexual exposure.

The murine cytomegalovirus chemokine homolog, m131/129, is a determinant of viral pathogenicity

Chemokines are important mediators of the early inflammatory response to infection and modify a wide range of host immune responses. Functional homologs of cellular chemokines have been identified in a number of herpesviruses, suggesting that the subversion of the host chemokine response contributes to the pathogenesis of these viruses. Transcriptional and reverse transcription-PCR analyses demonstrated that the murine cytomegalovirus (MCMV) chemokine homolog, m131, was spliced at the 3' end to the adjacent downstream open reading frame, m129, resulting in a predicted product of 31 kDa, which is significantly larger than most known chemokines. The in vivo impact of m131/129 was investigated by comparing the replication of MCMV mutants having m131/129 deleted (Deltam131/129) with that of wild-type (wt) MCMV. Our studies demonstrate that both wt and Deltam131/129 viruses replicated to equivalent levels during the first 2 to 3 days following in vivo infection. However, histological studies demonstrated that the early inflammatory response elicited by Deltam131/129 was reduced compared with that of wt MCMV. Furthermore, the Deltam131/129 mutants failed to establish a high-titer infection in the salivary glands. These results suggest that m131/129 possesses proinflammatory properties in vivo and is important for the dissemination of MCMV to or infection of the salivary gland. Notably, the Deltam131/129 mutants were cleared more rapidly from the spleen and liver during acute infection compared with wt MCMV. The accelerated clearance of the mutants was dependent on NK cells and cells of the CD4(+) CD8(+) phenotype. These data suggest that m131/129 may also contribute to virus mechanisms of immune system evasion during early infection, possibly through the interference of NK cells and T cells.

Five-transmembrane domains appear sufficient for a G protein-coupled receptor: functional five-transmembrane domain chemokine receptors

The putative seven-transmembrane (TM) domains have been the structural hallmark for the superfamily of heterotrimeric G protein-coupled receptors (GPCRs) that regulate a variety of cellular functions by mediating a large number of extracellular signals. Five-TM GPCR mutants of chemokine receptor CCR5 and CXCR4, the N-terminal segment of which connected directly to TM3 as a result of a deletion of TM1-2 and the first intracellular and extracellular loops, have been obtained in this study. Laser confocal microscopy and flow cytometry analysis revealed that these five-TM mutant GPCRs were expressed stably on the cell surface after transfection into human embryonic kidney 293 cells. The five-TM CCR5 and CXCR4 functioned as normal chemokine receptors in mediating chemokine-stimulated chemotaxis, Ca2+ influx, and activation of pertussis toxin-sensitive G proteins. Like the wild-type GPCRs, the five-TM mutant receptors also underwent agonist-dependent internalization and desensitization and were subjected to regulation by GPCR kinases and arrestins. Our study indicates that five-TM domains, at least in the case of CCR5 and CXCR4, appear to meet the minimum structural requirements for a functional GPCR and suggests possible existence of functional five-TM GPCRs in nature during evolution.

Anti-HIV agent trichosanthin enhances the capabilities of chemokines to stimulate chemotaxis and G protein activation, and this is mediated through interaction of trichosanthin and chemokine receptors

Trichosanthin (TCS), an active protein component isolated from a traditional Chinese medicinal herb Trichosanthes kirilowii, has been shown to inhibit HIV infection and has been applied in clinical treatment of AIDS. The recent development that chemokines and chemokine receptors play important roles in HIV infection led us to investigate the possible functional interaction of TCS with chemokines and their receptors. This study demonstrated that TCS greatly enhanced both RANTES (regulated upon activation, normal T cell expressed and secreted)- and stromal cell-derived factor (SDF)-1 alpha-stimulated chemotaxis (EC50 approximately equal to 1 nM) in leukocytes (THP-1, Jurkat, and peripheral blood lymphocyte cells) and activation of pertussis toxin-sensitive G proteins (EC50 approximately equal to 20 nM). TCS also significantly augmented chemokine-stimulated activation of chemokine receptors CCR5 and CXCR4 as well as CCR1, CCR2B, CCR3, and CCR4 transiently expressed in HEK293 cells. A mutant TCS with 4,000-fold lower ribosome-inactivating activity showed similar augmentation activity as wild-type TCS. Moreover, flow cytometry demonstrated that the specific association of TCS to the cell membranes required the presence of chemokine receptors, and laser confocal microscopy reveals that TCS was colocalized with chemokine receptors on the membranes. The results from TCS-Sepharose pull-down and TCS and chemokine receptor coimmunoprecipitation and cross-linking experiments demonstrated association of TCS with CCR5. Thus, our data clearly demonstrated that TCS synergizes activities of chemokines to stimulate chemotaxis and G protein activation, and the effects of TCS are likely to be mediated through its interaction with chemokine receptors.

Real-time analysis of integrin-mediated chemotactic migration of T lymphocytes within 3-D extracellular matrix-like gels

We have developed a novel 3-D gel reconstituted with major extracellular matrix (ECM) glycoproteins to follow the dynamics of migration of human T cells locomoting, in real-time, on gradients formed by representative chemoattractants: the C-C chemokine RANTES, and the pro-inflammatory cytokine IL-2. In the absence of chemoattractants, none of the T cells migrated directionally and the levels of random migration or cell polarization were low. However, major fractions of T cells placed in IL-2 and RANTES gradients in the gels polarized immediately after exposure to the chemoattractants. Shortly after polarization, 25% of the T cells migrated, in either a random or directional fashion, towards the sources of the chemoattractants; additional 5-10% of the cells remained polarized but stationary. The number of T cells migrating directionally towards RANTES or IL-2 peaked along with the formation of the chemotactic gradients. The directional migration of T cells was increased by a short pre-exposure to low doses of IL-2, which did not alter the level of expression of the beta1 integrins. The directional migration of T cells towards IL-2 and RANTES was mediated by IL-2R and pertussis toxin-sensitive receptors, respectively, and the directional, and to a lesser degree, the random locomotion of T cells induced by both chemoattractants required intact tyrosine kinase signaling and activities of the alpha4, alpha5, and, to a lesser degree, the alpha2 and alpha6 members the beta1 integrins. Our system enables the real-time tracking of individual locomoting lymphocytes and the analysis of their dynamic interactions with ECM components and cytokines.