Contrasting roles for IL-22 in DSS-induced colitis (38.7)

Interleukin (IL)-22 is a multifunctional cytokine with diverse biological activities which include involvement in the inflammatory response, tissue repair and pathogen defense. Recently, IL-22 was shown to be protective in two models of inflammatory bowel disease (IBD) in mice. In order to confirm those results and develop a reagent that could serve as a therapy, we generated IL-22-Fc which had an increased half-life relative to recombinant IL-22 (rIL-22). The effects of rIL-22 versus IL-22-Fc were compared in dextran sulphate sodium (DSS)-induced colitis. Prophylactic, but not therapeutic, administration of either rIL-22 or IL-22-Fc prevented disease and was significantly more efficacious than granulocyte macrophage colony stimulating factor (GM-CSF), a cytokine that has been used clinically in human IBD patients. The mechanism of the protective effect of IL-22 was in part driven by reduced circulating levels of inflammatory cytokines and enhanced proliferation/regeneration of the colonic epithelium. However, IL-22-Fc exacerbated weight loss and induced anemia. Thus, although prophylactic IL-22R stimulation protected animals from DSS-induced colitis, metabolic effects such as iron deficiency and weight loss complicate the benefit received. These data demonstrate that IL-22 can simultaneously play beneficial and detrimental roles in inflammatory diseases.

Identification of functional roles for both IL-17RB and IL-17RA in mediating IL-25-induced activities

IL-25 (IL-17E) is a unique IL-17 family ligand that promotes Th2-skewed inflammatory responses. Intranasal administration of IL-25 into naive mice induces pulmonary inflammation similar to that seen in patients with allergic asthma, including increases in bronchoalveolar lavage fluid eosinophils, bronchoalveolar lavage fluid IL-5 and IL-13 concentrations, goblet cell hyperplasia, and increased airway hyperresponsiveness. IL-25 has been reported to bind and signal through IL-17RB (IL-17BR, IL-17Rh1). It has been demonstrated recently that IL-17A signals through a heteromeric receptor composed of IL-17RA and IL-17RC. We sought to determine whether other IL-17 family ligands also utilize heteromeric receptor complexes. The required receptor subunits for IL-25 biological activities were investigated in vitro and in vivo using a combination of knockout (KO) mice and antagonistic Abs. Unlike wild-type mice, cultured splenocytes from either IL-17RB KO or IL-17RA KO mice did not produce IL-5 or IL-13 in response to IL-25 stimulation, and both IL-17RB KO and IL-17RA KO mice did not respond to intranasal administration of IL-25. Furthermore, treatment with antagonistic mAbs to either IL-17RB or IL-17RA completely blocked IL-25-induced pulmonary inflammation and airway hyperresponsiveness in naive BALB/c mice, similar to the effects of an antagonistic Ab to IL-25. Finally, a blocking Ab to human IL-17RA prevented IL-25 activity in a primary human cell-based assay. These data demonstrate for the first time that IL-25-mediated activities require both IL-17RB and IL-17RA and provide another example of an IL-17 family ligand that utilizes a heteromeric receptor complex.

ICOS and B7 costimulatory molecule expression identifies activated cellular subsets in rheumatoid arthritis

To better define important cell subsets expressing activation markers in rheumatoid arthritis (RA), we compared selective lymphocyte and monocyte B7H1, B7H2, B7RP.1, B7RP.2, and inducible costimulatory molecule (ICOS) expression from normal peripheral blood (NL PB), RA PB, and RA synovial fluid (SF) by multicolor flow cytometry and immunohistochemistry. RA SF memory lymphocytes expressed B7RP.1 and B7RP.2, suggesting that T-cells may function as antigen presenting cells (APCs) in RA joints. We found similar results for ICOS expression. RA SF CD14+ monocytes also expressed B7RP.1 (an ICOS ligand) and the homologous ligand B7RP.2, identifying monocytes as potential mediators of antigen processing and lymphocyte activation in RA. Furthermore, we found an increased population of RA SF CD14+ monocytes expressing B7H1 and B7H2. [The FACS analysis was supported by immunohistochemistry, showing intense lymphocyte and APC (macrophages with dendritic morphology) ICOS staining in RA synovial tissue (ST). Overall, these results define elevated populations of memoryT-lymphocytes expressing proinflammatory B7 molecules in RA SF that either stimulate T cells through ICOS (via ICOS ligands B7RP.1 and B7RP.2), or down-regulate RA ST T-lymphocytes through B7H1 and B7H2.] Therefore, in the same joint, there may exist positive and negative influences on the inflammatory response, and perhaps, the negative signals dominate as joint inflammation resolves.

Involvement of CD14, toll-like receptors 2 and 4, and MyD88 in the host response to the fungal pathogen Cryptococcus neoformans in vivo

The major capsular polysaccharide of Cryptococcus neoformans, glucuronoxylomannan (GXM), is recognized by Toll-like receptor 2 (TLR2), TLR4, and CD14. In these studies, mice deficient in CD14, TLR2, TLR4, and the TLR-associated adaptor protein, MyD88, were utilized to investigate the contribution of TLRs and CD14 to in vivo host defenses against C. neoformans. MyD88(-/-) mice had significantly reduced survival compared with wild-type C57BL/6 mice after intranasal (i.n.) and intravenous (i.v.) infection with live C. neoformans. CD14(-/-) mice had reduced survival when infected i.v., while TLR2(-/-) mice died significantly earlier after i.n. infection. Mortality was similar comparing TLR4 mutant C3H/HeJ mice and control C3H/HeOuJ mice following i.v. or i.n. challenge with C. neoformans. The course of pulmonary cryptococcosis was studied in more detail in the CD14(-/-), TLR2(-/-), and MyD88(-/-) mice. MyD88(-/-) mice infected i.n. had higher numbers of CFU in the lungs as well as higher GXM levels in the sera and lungs 7 days after infection than wild-type mice did. Surprisingly, there were no major differences in the levels of tumor necrosis factor alpha, interleukin-4 (IL-4), IL-10, IL-12p70, or gamma interferon in the lungs of C. neoformans-infected knockout mice compared with wild-type mice. Histopathologic analysis of the lungs on day 7 postinfection revealed minimal inflammation in all mouse groups. These studies demonstrate a major role for MyD88 and relatively minor roles for CD14 and TLR2 in the response to cryptococcal infection, with the decreased survival of MyD88(-/-) mice correlating with increased numbers of lung CFU and serum and lung GXM levels.

Cryptococcus neoformans Kin1 protein kinase homologue, identified through a Caenorhabditis elegans screen, promotes virulence in mammals

Cryptococcal infections are a global cause of significant morbidity and mortality. Recent studies support the hypothesis that virulence of Cryptococcus neoformans may have evolved via survival selection in environmental hosts, such as amoebae and free-living nematodes. We used killing of the nematode Caenorhabditis elegans by C. neoformans as an assay to screen a library of random C. neoformans insertion mutants. Of 350 mutants tested, seven were identified with attenuated virulence that persisted after crossing the mutation back into a wild-type strain. Genetic analysis of one strain revealed an insertion in a gene homologous to Saccharomyces cerevisiae KIN1, which encodes a serine/threonine protein kinase. C. neoformans kin1 mutants exhibited significant defects in virulence in murine inhalation and haematogenous infection models and displayed increased binding to alveolar and peritoneal macrophages. The kin1 mutant phenotypes were complemented by the wild-type KIN1 gene. These findings show that the C. neoformans Kin1 kinase homologue is required for full virulence in disparate hosts and that C. elegans can be used as a substitute host to identify novel factors involved in fungal pathogenesis in mammals.

Protective efficacy of antigenic fractions in mouse models of cryptococcosis

Infections due to the encapsulated fungus Cryptococcus neoformans are a significant cause of morbidity and mortality in patients with impaired T-cell function, particularly those with AIDS. Presumably then, T-cell responses to cryptococcal antigens are critical for protection against this ubiquitous fungus. To test the protective efficacy of these antigens as vaccine candidates, secreted cryptococcal antigens were separated by concanavalin A affinity chromatography into adherent (mannoprotein [MP]) and nonadherent (flowthrough [FT]) fractions, and the fractions were tested in murine models of disseminated cryptococcosis. Compared with adjuvant alone, C57BL/6 mice that received two inoculations of MP and FT exhibited prolonged survival and reduced brain and kidney fungal loads following intravenous challenge with C. neoformans strain B3501. MP-immunized animals had increased brain levels of tumor necrosis factor alpha, gamma interferon, and interleukin-2. Histopathologic examination revealed that compared with organs from mice that received only adjuvant, MP-immunized mice were able to recruit a stronger cellular infiltrate in brain, kidney, and liver in response to cryptococcal infection. Conjugated O-linked glycans were necessary for optimal MP-mediated protection, because chemical O deglycosylation reduced the protective efficacy of MP immunization. FT and MP immunization protected B-cell-deficient, but not T-cell-deficient mice, suggesting that protection was T-cell mediated. CBA/J mice also benefited from immunization with FT and MP, although the benefits were more modest than those seen with C57BL/6 mice. Thus, both MP and FT fractions of C. neoformans contain components that protect mice from disseminated cryptococcosis, and this protection appears to be T-cell mediated.

Disruption of the ICOS-B7RP-1 costimulatory pathway leads to enhanced hepatic immunopathology and increased gamma interferon production by CD4 T cells in murine schistosomiasis

Morbidity and mortality in schistosomiasis are largely due to an immune response mediated by CD4 T lymphocytes. Since lymphocyte activation is shaped by costimulatory signals, the specific functions of different costimulatory pathways are of increasing interest. We now examined the role of the inducible costimulatory molecule (ICOS) and its ligand B7-related protein 1 (B7RP-1) in the experimental murine schistosome infection by blocking this costimulatory pathway with monoclonal antibody against ICOS, administered daily by intraperitoneal injection during the patent phase of the disease. The treated mice exhibited enhanced hepatic immunopathology characterized by enlarged egg granulomas and pronounced parenchymal inflammation with hepatocellular necrosis, resulting in elevated liver enzyme levels in serum. Most strikingly, there was a sharp increase in gamma interferon (IFN-gamma) production by schistosome egg antigen-stimulated granuloma cells, bulk mesenteric lymph node (MLN) cells, and purified MLN CD4 T cells, which contrasted with a more discreet change in the Th2-type cytokines interleukin 4 (IL-4) and IL-10. These findings suggest that the ICOS-B7RP-1 costimulatory pathway serves primarily to control IFN-gamma production, thereby promoting a cytokine environment conducive to limited hepatic damage.

Programmed death-1 targeting can promote allograft survival

The recently identified CD28 homolog and costimulatory molecule programmed death-1 (PD-1) and its ligands, PD-L1 and PD-L2, which are homologs of B7, constitute an inhibitory regulatory pathway of potential therapeutic use in immune-mediated diseases. We examined the expression and functions of PD-1 and its ligands in experimental cardiac allograft rejection. In initial studies, we found that most normal tissues and cardiac isografts had minimal expression of PD-1, PD-L1, or PD-L2, but intragraft induction of all three molecules occurred during development of cardiac allograft rejection. Intragraft expression of all three genes was maintained despite therapy with cyclosporin A or rapamycin, but was prevented in the early posttransplant period by costimulation blockade using CD154 or anti-inducible costimulator mAb. We prepared PD-L1.Ig and PD-L2.Ig fusion proteins and showed that each bound to activated PD-1(+) T cells and inhibited T cell functions in vitro, thereby allowing us to test the effects of PD-1 targeting on allograft survival in vivo. Neither agent alone modulated allograft rejection in wild-type recipients. However, use of PD-L1.Ig administration in CD28(-/-) recipients, or in conjunction with immunosuppression in fully MHC-disparate combinations, markedly prolonged cardiac allograft survival, in some cases causing permanent engraftment, and was accompanied by reduced intragraft expression of IFN-gamma and IFN-gamma-induced chemokines. PD-L1.Ig use also prevented development of transplant arteriosclerosis post-CD154 mAb therapy. These data show that when combined with limited immunosuppression, or in the context of submaximal TCR or costimulatory signals, targeting of PD-1 can block allograft rejection and modulate T and B cell-dependent pathologic immune responses in vivo.

The ribonuclease protection assay: a powerful tool for the veterinary pathologist

Veterinary pathologists engaged in basic research use a variety of methods to study disease pathogenesis at the light microscopic and submicroscopic (protein and mRNA) levels. The ribonuclease protection assay is a sensitive and accurate method to measure mRNA expression. The major advantages of the assay are that multiple mRNA species can be measured simultaneously in a single total RNA sample and that the assay has relatively high throughput. The major disadvantage is that the assay requires moderate technical skill.

Selective lymphocyte chemokine receptor expression in the rheumatoid joint

OBJECTIVE

In patients with rheumatoid arthritis (RA), chemokines and their receptors are important for lymphocyte trafficking into the inflamed joint. This study was undertaken to characterize the expression of chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CXCR3, and CX3CR1 in normal (NL) peripheral blood (PB), RA PB, and RA synovial fluid (SF).

METHODS

Using flow cytometry, immunohistochemistry, and 2-color immunofluorescence, we defined the expression of chemokine receptors on CD3+ T lymphocytes in RA synovial tissue (ST), RA SF, RA PB, and NL PB.

RESULTS

The percentage of CD3+ lymphocytes expressing CCR2, CCR4, CCR5, and CX3CR1 was significantly elevated in RA PB compared with that in NL PB, while the percentage of CD3+ lymphocytes expressing CCR5 was significantly enhanced in RA SF compared with that in NL and RA PB. In contrast, similar percentages of CD3+ lymphocytes in NL PB, RA PB, and RA SF expressed CCR6 and CXCR3. Immunohistochemistry of RA ST showed lymphocyte expression of CCR4, and 2-color immunofluorescence staining revealed RA ST CD3+ lymphocytes intensely immunoreactive for CXCR3, suggesting that these 2 receptors may be particularly important for CD3+ lymphocyte trafficking to the inflamed joint. In comparisons of chemokine receptor expression on naive (CD45RA+) and memory (CD45RO+) CD3+ lymphocytes, there were greater percentages of memory CD3+/CD4+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD4+ lymphocytes in RA PB and RA SF, and greater percentages of memory CD3+/CD8+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD8+ lymphocytes in RA SF, suggesting receptor up-regulation upon lymphocyte activation. In contrast, percentages of CD3+/CD8+ memory lymphocytes expressing CX3CR1 were significantly less than percentages of naive CD3+/CD8+ lymphocytes in RA PB, suggesting that this receptor may be down-regulated upon lymphocyte activation. A major difference between the RA PB and NL PB groups was significantly more CCR4+ memory leukocytes and memory CCR5+/ CD3+/CD8+ lymphocytes in RA PB than NL PB, further suggesting that these receptors may be particularly important for lymphocyte homing to the RA joint.

CONCLUSION

These results identify CCR4, CCR5, CXCR3, and CX3CR1 as critical chemokine receptors in RA.

Targeted deletion of CX(3)CR1 reveals a role for fractalkine in cardiac allograft rejection

Fractalkine (Fk) is a structurally unusual member of the chemokine family. To determine its role in vivo, we generated mice with a targeted disruption of CX(3)CR1, the receptor for Fk. CX(3)CR1(-/-) mice were phenotypically indistinguishable from wild-type mice in a pathogen-free environment. In response to antibody-induced glomerulonephritis, CX(3)CR1(-/-) and CX(3)CR1(+/+) mice had similar levels of proteinuria and injury. CX(3)CR1(-/-) and CX(3)CR1(+/+) mice also developed similar levels of disease in myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis. We performed heterotopic MHC class I/II cardiac transplants from BALB/c mice into C57BL/6 mice. In the absence of cyclosporin A (CsA), there was no difference in graft survival time between CX(3)CR1(-/-) and CX(3)CR1(+/+) recipient mice. However, in the presence of subtherapeutic levels of CsA, graft survival time was significantly increased in the CX(3)CR1(-/-) mice. Characterization of cells infiltrating the grafts revealed a selective reduction in natural killer cells in the CX(3)CR1(-/-) recipients in the absence of CsA and a reduction in macrophages, natural killer cells, and other leukocytes in the presence of CsA. We conclude that Fk plays an important role in graft rejection. The development of CX(3)CR1 antagonists may allow reductions in the doses of immunosuppressive drugs used in transplantation.

The costimulatory molecule ICOS plays an important role in the immunopathogenesis of EAE

The inducible costimulatory molecule (ICOS) is expressed on activated T cells and participates in a variety of important immunoregulatory functions. After the induction of experimental allergic encephalomyelitis in SJL mice with proteolipid protein (PLP), brain ICOS mRNA and protein were up-regulated on infiltrating CD3+ T cells before disease onset. ICOS blockade during the efferent immune response (9-20 days after immunization) abrogated disease, but blockade during antigen priming (1-10 days after immunization) exacerbated disease. Upon culture with PLP and compared with immunized controls, splenocytes produced either decreased interferon-gamma (IFN-gamma, in efferent blockade) or excessive IFN-gamma (in priming blockade). PLP-specific immunoglobulin G1 was decreased in animals treated with anti-ICOS during antigen priming, but not in other groups.

Importance of ICOS-B7RP-1 costimulation in acute and chronic allograft rejection

Primary T cell activation requires B7-CD28 and CD40-CD154 costimulation, but effector T cell functions are considered to be largely independent of these costimulatory pathways. Although blockade of costimulation with cytolytic T lymphocyte-associated antigen 4-immunoglobulin (CTLA-4-Ig) or monoclonal antibody (mAb) to CD154 prolongs allograft survival, chronic rejection follows, which suggests that additional key costimulatory pathways are active in vivo. We found that both antibody to inducible costimulator (anti-ICOS) and an ICOS-Ig fusion protein suppressed intragraft T cell activation and cytokine expression and prolonged allograft survival in a manner similar to that in ICOS-/- allograft recipients. The combination of anti-ICOS therapy and cyclosporin A led to permanent engraftment. In addition, ICOS-B7RP-1 costimulation was required for the development of chronic rejection after CD40-CD154 blockade. These data demonstrate a key role for the ICOS-B7RP-1 pathway in acute and chronic rejection and highlight the benefits of targeting this pathway in combination with the use of conventional immunosuppressive agent.

ICOS is critical for T helper cell-mediated lung mucosal inflammatory responses

We examined the requirement for and cooperation between CD28 and inducible costimulator (ICOS) in effective T helper (TH) cell responses in vivo. We found that both CD28 and ICOS were critical in determining the outcome of an immune response; cytolytic T lymphocyte-associated antigen 4-immunoglobulin (CTLA-4-Ig), ICOS-Ig and/or a neutralizing ICOS monoclonal antibody attenuated T cell expansion, TH2 cytokine production and eosinophilic inflammation. CD28-dependent signaling was essential during priming, whereas ICOS-B7RP-1 regulated TH effector responses, and the up-regulation of chemokine receptors that determine T cell migration. Our data suggests a scenario whereby both molecules regulate the outcome of the immune response but play separate key roles: CD28 primes T cells and ICOS regulates effector responses.

Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis

OBJECTIVE

Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects.

METHODS

We compared chemokine receptor expression on CD14+ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68+ macrophages.

RESULTS

Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68+ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)- and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1alpha (MIP-1alpha) was principally restricted to vascular endothelium, and MIP-1beta+ macrophages were found throughout the sections.

CONCLUSION

Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.

DIFFERENTIAL NF-??B AND I??B GENE EXPRESSION DURING DEVELOPMENT OF CARDIAC ALLOGRAFT REJECTION VERSUS CD154 MONOCLONAL ANTIBODY-INDUCED TOLERANCE1

BACKGROUND

The Rel/NF-kappaB transcription factor pathway, regulated by IkappaB proteins, is considered central to immune responses, although there are surprisingly few in vivo data concerning alloresponses.

METHODS

We undertook analysis of NF-kappaB and IkappaB mRNA intracardiac allograft expression, and NF-kappaB nuclear translocation, during acute rejection versus CD154 monoclonal antibody (mAb)-induced tolerance induction in fully MHC-disparate mice.

RESULTS

Intragraft expression of all nine NF-kappaB and IkappaB genes increased during development of rejection, and nuclear translocation of p50, p52, and p65 was detected. CD154 mAb therapy decreased mRNA levels of all nine NF-kappaB and IkappaB genes, and impaired nuclear translocation of p50, p52, and p65 NF-kappaB proteins. However, prolonged survival could not be induced by CD154 mAb in p50- or p52-deficient allograft recipients, indicating an absolute requirement for expression of these genes in CD154 mAb-induced tolerance.

CONCLUSIONS

We conclude that, whereas blanket approaches to NF-kappaB suppression are unlikely to be effective strategies for tolerance induction, a better understanding of the roles of individual NF-kappaB and IkappaB genes may allow development of more precise and effective therapies.

Potential role of the chemokine receptors CXCR3, CCR4, and the integrin alphaEbeta7 in the pathogenesis of psoriasis vulgaris

Various adhesion molecules have been implicated in T lymphocyte binding to dermal vascular endothelium in psoriasis vulgaris, but the chemotactic signals that promote subsequent homing into the adjacent dermis and overlying epidermis are poorly defined. We studied chemokine receptor (CCR1-CCR5, CXCR1-CXCR3), chemokine (interferon-gamma inducible protein 10 [IP-10]), monokine induced by interferon-gamma (MIG), thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC), and adhesion molecule (cutaneous lymphocyte antigen [CLA], E-selectin, lymphocyte function-associated antigen-1 [LFA-1], intercellular adhesion molecule-1 [ICAM-1], very late antigen 4 [VLA-4], vascular cell adhesion molecule-1 [VCAM-1], alphaEbeta7, and E-cadherin) expression in psoriasis by immunohistology, flow cytometry, and molecular techniques. CXCR3 and CCR4 were expressed by dermal CD3+ lymphocytes, and their chemokine ligands, IP-10, MIG, TARC, and MDC, were up-regulated in psoriatic lesions. Keratinocytes stimulated with tumor necrosis factor-alpha and interferon-gamma up-regulated expression of IP-10, MIG, and MDC mRNA, whereas dermal endothelial cells, similarly stimulated, up-regulated expression of IP-10, MDC, and TARC mRNA, suggesting that these cell types were sources of the chemokines detected in biopsies. There was enhanced expression of E-selectin, CLA, LFA-1, ICAM-1, VLA-4, VCAM-1, and alphaEbeta7 in psoriatic lesions versus nonlesional skin. Finally, intra-epidermal CLA+ and alphaEbeta7+ T lymphocytes selectively expressed the chemokine receptor CXCR3. Collectively, these data suggest that CXCR3 and CCR4 may be involved in T lymphocyte trafficking to the psoriatic dermis and that CXCR3 is selectively involved in subsequent T cell homing to the overlying epidermis.

Leukocyte recruitment during onset of experimental allergic encephalomyelitis is CCR1 dependent

We have shown that macrophages and microglia present within demyelinating plaques of patients with multiple sclerosis (MS) are immunoreactive for the chemokine receptor CCR1 and its ligand, macrophage inflammatory protein-1alpha. To test the importance of CCR1 to the pathogenesis of MS, we studied the progression of experimental allergic encephalomyelitis (EAE) in CCR1(+/+) vs. CCR1(-/-) mice. After immunization with myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide, nearly all CCR1(+/+) mice developed EAE (95% incidence, severity 2.5+/-0.1), whereas CCR1(-/-) mice had less severe disease (55% incidence, p<0.001; severity 1. 2+/-0.2, p<0.001). CCR1(+/+) mice showed elevated brain mRNA for the chemokines immune protein (IP)-10, RANTES and monocyte chemoattractant protein-1 prior to disease onset, whereas only IP-10 mRNA was elevated in CCR1(-/-) mice. Both groups of mice had comparable in vitro lymphocyte proliferation and cytokine production upon stimulation with MOG peptide, and similar cutaneous hypersensitivity responses to 2,4-dinitrofluorobenzene, suggesting that CCR1(-/-) mice were not systemically immunosuppressed. These data demonstrate that deletion of a chemokine receptor is at least partially protective in EAE, and suggest that targeting of CCR1 may be of therapeutic significance clinically.

Key role of chemokines and chemokine receptors in inflammation, immunity, neoplasia, and infectious disease

Leukocyte homing is a complex, multistep process involving the coordinated expression of adhesion molecules and certain chemotactic cytokines, termed chemokines. Although chemokines initially burst into the literature as potent inflammatory mediators, it is now clear that they are involved in a variety of processes including lymphocyte maturation, angiogenesis, and tumor growth. Furthermore, a variety of important pathogens manipulate various chemokine/receptor pathways to infect the host and evade the immune system.

CCR5(+) and CXCR3(+) T cells are increased in multiple sclerosis and their ligands MIP-1alpha and IP-10 are expressed in demyelinating brain lesions

Multiple sclerosis (MS) is a T cell-dependent chronic inflammatory disease of the central nervous system. The role of chemokines in MS and its different stages is uncertain. Recent data suggest a bias in expression of chemokine receptors by Th1 vs. Th2 cells; human Th1 clones express CXCR3 and CCR5 and Th2 clones express CCR3 and CCR4. Chemokine receptors expressed by Th1 cells may be important in MS, as increased interferon-gamma (IFN-gamma) precedes clinical attacks, and IFN-gamma injection induces disease exacerbations. We found CXCR3(+) T cells increased in blood of relapsing-remitting MS, and both CCR5(+) and CXCR3(+) T cells increased in progressive MS compared with controls. Furthermore, peripheral blood CCR5(+) T cells secreted high levels of IFN-gamma. In the brain, the CCR5 ligand, MIP-1alpha, was strongly associated with microglia/macrophages, and the CXCR3 ligand, IP-10, was expressed by astrocytes in MS lesions but not unaffected white matter of control or MS subjects. Areas of plaque formation were infiltrated by CCR5-expressing and, to a lesser extent, CXCR3-expressing cells; Interleukin (IL)-18 and IFN-gamma were expressed in demyelinating lesions. No leukocyte expression of CCR3, CCR4, or six other chemokines, or anti-inflammatory cytokines IL-5, IL-10, IL-13, and transforming growth factor-beta was observed. Thus, chemokine receptor expression may be used for immunologic staging of MS and potentially for other chronic autoimmune/inflammatory processes such as rheumatoid arthritis, autoimmune diabetes, or chronic transplant rejection. Furthermore, these results provide a rationale for the use of agents that block CCR5 and/or CXCR3 as a therapeutic approach in the treatment of MS.

Elevated interleukin-10-to-interleukin-12 ratio in feline immunodeficiency virus-infected cats predicts loss of type 1 immunity to Toxoplasma gondii

Similar to human immunodeficiency virus, feline immunodeficiency virus (FIV) induces immunodeficiency and enhanced susceptibility to secondary pathogens. To explore cytokine alterations in lentivirus immunodeficiency, constitutive mRNA expression was measured in lymph nodes of healthy and FIV-infected cats before and after challenge with Toxoplasma gondii. Cytokine mRNA expression was similar in control and FIV-infected cats during the first 10 weeks after infection. At 16 weeks, interferon (IFN)-gamma, tumor necrosis factor-alpha, and interleukin (IL)-10 mRNA were increased in FIV-infected cats. Challenge with T. gondii induced an increase in IL-2, IFN-gamma, and IL-12 in the lymph nodes of control cats, whereas IFN-gamma and IL-10 but not IL-2 or IL-12 increased in the lymph nodes of FIV-T. gondii coinfected cats. These results indicate that FIV immunodeficiency may derive from a failure to generate an IL-12-dependent type 1 response and that an elevated level of IL-10 mRNA expression is a predictor of lentivirus immunodeficiency.

Characterization of the cutaneous exanthem in macaques infected with a Nef gene variant of SIVmac239

The molecularly cloned viruses known as SIVmac239/R17Y and SIVmac239/YEnef cause extensive lymphocyte activation and induce an acute disease syndrome in macaque monkeys. One manifestation of this syndrome is a severe diffuse cutaneous maculopapular exanthem that is similar to the exanthem associated with HIV-1 infection. To examine the pathogenesis of this exanthem, biopsies obtained throughout the course of clinically evident rash were examined for the presence of virus by in situ hybridization and immunohistochemistry, and the cellular infiltrate was characterized with respect to cellular immunophenotype and chemokine receptor expression. The onset of rash was associated with abundant simian immunodeficiency virus nucleic acid and protein within perivascular dermal infiltrates and occasionally within intraepithelial cells. Analysis of cellular infiltrates showed that biopsies, obtained on the day of rash onset, were composed of equal numbers of CD4+ and CD8+ lymphocytes and abundant alphaEbeta7 positive cells surrounding vessels with upregulated endothelial E-selectin. Moreover, by examining virus expression in sequential skin biopsies from the same animal, the clearance of virus and the resolution of rash were associated with an increase in the percentage of cells expressing CD8, the chemokine receptor CXCR3, and GMP-17, a marker of cytotoxic granules. These results suggest that activated cytotoxic T cells are trafficking to sites of inflammation in the skin and directly or indirectly affect levels of viral replication at these sites.

Chemokine receptor expression on resident and inflammatory cells in the brain of macaques with simian immunodeficiency virus encephalitis

Although the mechanisms of human immunodeficiency virus (HIV) neuroinvasion, neuronal injury, and subsequent development of HIV-1-associated AIDS dementia complex are not fully understood, a correlation between monocyte/macrophage infiltrates in the brain and neurological disease exists. In light of the many potential roles that chemokines and chemokine receptors may play in HIV neuropathogenesis, we sought to describe their pattern of expression in the SIV-infected rhesus macaque model of HIV encephalitis. We previously demonstrated elevated expression of the chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, RANTES, and interferon-inducible protein (IP)-10 in brain of macaque monkeys with SIV encephalitis. In this study, we demonstrate that the corresponding chemokine receptors CCR3, CCR5, CXCR3, and CXCR4 are expressed in perivascular infiltrates in these same tissues. In addition, we detected CCR3, CCR5, and CXCR4 on subpopulations of large hippocampal and neocortical pyramidal neurons and on glial cells in both normal and encephalitic brain. These findings suggest that multiple chemokines and their receptors contribute to monocyte and lymphocyte recruitment to the brain in SIV encephalitis. Furthermore, the expression of known HIV/SIV co-receptors on neurons suggests a possible mechanism whereby HIV or SIV can directly interact with these cells, disrupting their normal physiological function and contributing to the pathogenesis of AIDS dementia complex.

The chemokine receptors CXCR3 and CCR5 mark subsets of T cells associated with certain inflammatory reactions

T cells infiltrating inflammatory sites are usually of the activated/memory type. The precise mechanism for the positioning of these cells within tissues is unclear. Adhesion molecules certainly play a role; however, the intricate control of cell migration appears to be mediated by numerous chemokines and their receptors. Particularly important chemokines for activated/memory T cells are the CXCR3 ligands IP-10 and Mig and the CCR5 ligands RANTES, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein-1beta. We raised anti-CXCR3 mAbs and were able to detect high levels of CXCR3 expression on activated T cells. Surprisingly, a proportion of circulating blood T cells, B cells, and natural killer cells also expressed CXCR3. CCR5 showed a similar expression pattern as CXCR3, but was expressed on fewer circulating T cells. Blood T cells expressing CXCR3 (and CCR5) were mostly CD45RO+, and generally expressed high levels of beta1 integrins. This phenotype resembled that of T cells infiltrating inflammatory lesions. Immunostaining of T cells in rheumatoid arthritis synovial fluid confirmed that virtually all such T cells expressed CXCR3 and approximately 80% expressed CCR5, representing high enrichment over levels of CXCR3+ and CCR5+ T cells in blood, 35 and 15%, respectively. Analysis by immunohistochemistry of various inflamed tissues gave comparable findings in that virtually all T cells within the lesions expressed CXCR3, particularly in perivascular regions, whereas far fewer T cells within normal lymph nodes expressed CXCR3 or CCR5. These results demonstrate that the chemokine receptor CXCR3 and CCR5 are markers for T cells associated with certain inflammatory reactions, particularly TH-1 type reactions. Moreover, CXCR3 and CCR5 appear to identify subsets of T cells in blood with a predilection for homing to these sites.