Required early complement activation in contact sensitivity with generation of local C5-dependent chemotactic activity, and late T cell interferon gamma: a possible initiating role of B cells

Multiple modes of action mediate the therapeutic effect of IVIg in experimental epidermolysis bullosa acquisita

Substitution of IgG in antibody deficiency or application of high-dose intravenous IgG (IVIg) in patients with autoimmunity are well-established treatments. Data on the mode of action of IVIg are, however, controversial and may differ for distinct diseases. In this study, we investigated the impact and molecular mechanism of high-dose IgG treatment in murine autoantibody-induced skin inflammation, namely, epidermolysis bullosa acquisita (EBA). EBA is caused by antibodies directed against type VII collagen (COL7) and is mediated by complement activation, release of reactive oxygen species, and proteases by myeloid cells. In murine experimental EBA the disease can be induced by injection of anti-COL7 IgG. Here, we substantiate that treatment with high-dose IgG improves clinical disease manifestation. Mechanistically, high-dose IgG reduced the amount of anti-COL7 in skin and sera, which is indicative for an FcRn-dependent mode-of-action. Furthermore, in a non-receptor-mediated fashion, high-dose IgG showed antioxidative properties by scavenging extracellular reactive oxygen species. High-dose IgG also impaired complement activation and served as substrate for proteases, both key events during EBA pathogenesis. Collectively, the non-receptor-mediated anti-inflammatory properties of high-dose IgG may explain the therapeutic benefit of IVIg treatment in skin autoimmunity.

CD5/CD20 expression on circulating B cells in HCV-related chronic hepatitis and mixed cryoglobulinemia

The role of CD5⁺ B cells in patients with HCV infection and HCV-related disorders, including mixed cryoglobulinemia (MC), has been addressed in previous reports with conflicting results. We established a correlation between CD5/CD20 expression on circulating B lymphocytes, characterizing monoclonal B cell lymphocytosis (MBL), and clinical features in a cohort of 45 patients with chronic HCV hepatitis [without MC: 23 patients (MC- group); with MC: 22 patients (MC+ group)], and 45 HCV-negative healthy subjects as controls. By flow cytometry analysis, three B cells phenotypes were singled out: 1) CD5⁺CD20^dim (CLL-like phenotype); 2) CD5⁺CD20^bright (atypical phenotype); and 3) CD5^-CD20⁺ phenotype. CD5⁺CD20^bright cells were reduced in MC- patients (p=0.049). CD5⁺CD20^dim B cells were significantly higher in group B than in the control group (p=0.003). ROC curve analysis in MC+ patients showed the highest positive likelihood ratio at ≥7.35% (p=0.008) for CLL-like phenotype and at ≤63.6% (p=0.03) for the CD5^-CD20⁺ B cell phenotype. HCV infection was associated with a higher frequency of CLL-like (odds ratio=16, p=0.002) and a lower frequency of atypical (odds ratio: 3.1, p=0.02) and CD5^-CD20⁺ (odds ratio: 11, p=0.01) phenotypes. The association with higher levels of CLL-like phenotype progressively increased from group of MC- patients (odds ratio: 9.3, p=0.04) to the group of MC+ patients (odds ratio: 25.1, p=0.0003). CONCLUSIONS: The occurrence of a CLL-like pattern may allow to identify HCV-infected patients at risk of developing MC and eventually non-Hodgkin lymphoma, who should require a closer surveillance and a longer follow-up.

A subset of AID-dependent B-1a cells initiates hypersensitivity and pneumococcal pneumonia resistance

We propose that there is a special B-1a B cell subset ("sB-1a" cells) that mediates linked processes very early after immunization to initiate cutaneous contact sensitivity (CS), delayed-type hypersensitivity (DTH), and immune resistance to pneumococcal pneumonia. Our published data indicate that in CS and DTH, these initiating processes are required for elicitation of the delayed onset and late-occurring classical T cell-mediated responses. sB-1a cells resemble memory B2 cells, as they are stimulated within 1 h of immunization and depend on T helper cytokines-uniquely IL-4 from hepatic iNKT cells--for activation and rapid migration from the peritoneal cavity to the spleen to secrete IgM antibody (Ab) and Ab-derived free light chains (FLCs) by only 1 day after immunization. Unlike conventional B-1a (cB-1a) cell-produced IgM natural Ab, IgM Ab produced by sB-1a cells has high Ag affinity owing to immunoglobulin V-region mutations induced by activation-induced cytidine deaminase (AID). The dominant cB-1a cells are increased in immunized AID-deficient mice but do not mediate initiation, CS, or pneumonia resistance because natural Ab has relatively low Ag affinity because of unmutated germ-line V regions. In CS and DTH, sB-1a IgM Ag affinity is sufficiently high to mediate complement activation for generation of C5a that, together with vasoactive mediators such as TNF-α released by FLC-sensitized mast cells, activate local endothelium for extravascular recruitment of effector T cells. We conclude by discussing the possibility of functional sB-1 cells in humans.

β-arrestin 2 inhibits proinflammatory chemokine production and attenuates contact allergic inflammation in the skin

β-Arrestins participate in G-protein receptor signaling and act as adapter proteins that direct the recruitment, activation, and scaffolding of various cytoplasmic signaling complexes. β-Arrestin 2-deficient (Arrb2(-/-)) mice show decreased T-cell recruitment into allergic lung tissue but increased neutrophil infiltration into wounded skin. Given these opposing effects in different immune cell subsets, we investigated the role of β-arrestin 2 in the regulation of contact hypersensitivity responses. We observed significantly increased allergic ear swelling to the obligate contact sensitizers DNFB and FITC in Arrb2(-/-) compared with wild-type mice. Immunohistological analyses revealed strikingly increased neutrophil infiltration with abundant subcorneal pustules in inflamed ear tissue of DNFB-allergic Arrb2(-/-) mice. Experiments involving adoptive transfers of sensitized lymphocytes and bone marrow chimeric mice indicated that β-arrestin 2 exerts its anti-inflammatory effects predominantly through radioresistant, skin-resident cells in the challenge phase of contact hypersensitivity. As a potential mechanism, we found that primary cultures of β-arrestin 2-deficient keratinocytes secreted higher levels of neutrophil-attracting chemokines including CXCL1/KC in response to T cell-derived cytokines in vitro. These experimental results support a model in which β-arrestin 2 inhibits the production of proinflammatory chemokines, which limits the recruitment of myeloid immune cells and thereby attenuates allergic skin inflammation.

Disruption of the complement anaphylatoxin receptor C5L2 exacerbates inflammation in allergic contact dermatitis

The complement anaphylatoxin C5a is a critical mediator of allergic contact dermatitis, bridging essential aspects of innate and adaptive immunity. This anaphylatoxin functions by interacting with two 7-transmembrane segment receptors, the C5aR and C5L2. The C5aR is a classical G protein coupled receptor, whereas C5L2 is deficient in coupling to G proteins because of variations in the sequence. Our previous work in human neutrophils revealed a unique role for C5L2 in negatively modulating anaphylatoxin receptor mediated cellular activation through interactions with β-arrestin. When C5L2 is deficient, C5aR-mediated β-arrestin signaling is greatly enhanced. The work described in this study was undertaken first to determine the effect of C5L2 deficiency in a murine model of contact sensitivity, and second to determine whether the resultant exacerbation of inflammatory parameters reflects a negative modulatory function of C5L2 on the C5aR. First, we find dramatic increases in inflammation in C5L2(-/-) animals compared with wild type mice. Second, these increases are completely reversed following administration of mAb against the C5aR. Thus, in allergic contact sensitivity, as in isolated human neutrophils, C5L2 functions to suppress C5a-C5aR-mediated responses, further underscoring its role as a negative regulator of anaphylatoxin activity.

The lymphocyte immunophenotypical pattern in chronic lymphocytic leukemia associated with hepatitis viral infections

BACKGROUND

Chronic lymphoproliferative disorders (CLD) are frequently found in patients with hepatitis viral infections, which can lead to changes in pathogenesis. Hepatitis viruses are hepatotrope viruses, potentially lymphotrope and also potentially oncogenic (hepatocellular carcinoma) viruses. HBV and HCV are involved in autoimmune disorders and in the ethiopathogeny of chronic lymphoproliferative disorders.

AIM

Detection of immunophenotype changes of malignant lymphocytes in CLD--especially CLL--associated with hepatitis viral infections.

MATERIALS AND METHODS

Bone marrow aspirate, peripheral blood samples on EDTA were available for analysis from 58 patients from a follow-up schedule of the Department of Hematology SUUB from March 2008 until June 2009. The patients were diagnosed with chronic lymphoproliferative disorders associated with hepatitis virus B/C/D infections. A group of 28 consecutive unselected patients with CLL who met the diagnostic criteria of the National Cancer Institute-Working Group (NCI NCIWG), and associated hepatitis viral infection (v-CLL) were studied for the expression of several immunophenotypical markers, in comparison to CLL patients without viral infection (control group). Immunophenotyping analysis was performed on a FACS Calibur flowcytometer with a large panel according to EGIL/WHO recommendations. The diagnosis was completed after the histological and immunochemical analysis from tumoral lesions.

RESULTS

Demographics characteristics--male/female ratio 1/2, average age 64 years. Disease type: 90% B-CLD, 5% T-CLD, 5% Hodgkin's disease. The viral infections: 58.53% HCV, 34.41% HBV, 2.43% HBV+HDV, 2.43% HCV+HDV, 2.43% HBV+HCV+HDV. We found in CLL with viral coinfection (v-CLL) cases an elevated expression of B-cell markers--CD19 (Md95/92), CD20 (Md 90/39), CD79b (Md58/31), CD23 (Md67/37). Poor prognosis markers have a higher expression in v-CLL: CD38 (Md49/24), Bcl2 (Md 46/5), cyclin D19 (Md 11/0.5). No change in ZAP-70 expression was observed: Md 59.5/59.1.

DISCUSSIONS

Hepatitis viruses could be involved in the pathogenesis of CLD, but as a trigger for a more aggressive outcome. Higher expression of B-cell markers CD19, CD20 in CLL with viral infection suggests a change to atypical CLL, sustained by elevated expression of known poor prognosis markers bcl-2, cyclin D1 and CD38. Lack of ZAP-70 expression could be explained by a strong correlation with a basic unmutated IgVH status, not related to the viral infection. We found a higher frequency of HCV infection in patients with CLD and especially in CLL patients, which were analyzed extensively for immunophenotypical changes. In the present study, we demonstrated that this CD5+ B cell population with clonal expansion, defining CLL patients, has a different immunophenotype, probably related to the hepatitis viral infection.

Participation of iNKT cells in the early and late components of Tc1-mediated DNFB contact sensitivity: cooperative role of γδ-T cells

Prior studies of classical 24 h responses in TNP-Cl (picryl chloride) allergic contact sensitivity (CS), showed mediation by Th1 cells in CBA mice, and established that 24 h elicitation of responses requires an early 2 h CS-initiating component dependent on iNKT cells, IL-4 and B-1 B cells. Here, we studied the other form of cytotoxic T cell (Tc1) CS in DNFB sensitized BALB/c mice and determined that similar CS-initiation also is required. We systematically tested each step of the initiation pathway in this model. Thus, DNFB Tc1 CS was significantly impaired in iNKT cell deficient CD1d(-/-) and Jα18(-/-) mice, IL4Rα(-/-) and STAT-6(-/-) mice, and also in pan B-cell deficient JH(-/-) mice. Further, the Tc1 DNFB CS-initiating component, like Th1 response to TNP-Cl, was elicited by only 1-day after immunization, due to B-1 cells. In summary, we show that CS-Initiation also is required in Tc1 CS. Further, we have newly determined regulatory support of both the early and late components of DNFB induced Tc1 CS by iNKT cells and γδ-T cells. In summary, both iNKT cells and assisting γδ-T cells are involved in initiating and effector phases of DNFB induced CS.

Imunopatologia da dermatite de contato alérgica

A dermatite de contato alérgica é consequência de uma reação imune mediada por células T contra químicos de baixo peso molecular, denominados haptenos. É uma condição frequente que ocorre em todas as raças e faixas etárias e afeta a qualidade de vida de seus portadores. O mecanismo imunológico desta doença vem sendo revisto nas últimas décadas com significativo avanço no seu entendimento. A metabolização e o caminho dos haptenos, bem como a formação e o mecanismo de ação das células responsáveis tanto pela reação quanto pelo seu término, são discutidos neste artigo

The Vaccinia virus complement control protein modulates adaptive immune responses during infection

Complement activation is an important component of the innate immune response against viral infection and also shapes adaptive immune responses. Despite compelling evidence that complement activation enhances T cell and antibody (Ab) responses during viral infection, it is unknown whether inhibition of complement by pathogens alters these responses. Vaccinia virus (VACV) modulates complement activation by encoding a complement regulatory protein called the vaccinia virus complement control protein (VCP). Although VCP has been described as a virulence factor, the mechanisms by which VCP enhances VACV pathogenesis have not been fully defined. Since complement is necessary for optimal adaptive immune responses to several viruses, we hypothesized that VCP contributes to pathogenesis by modulating anti-VACV T cell and Ab responses. In this study, we used an intradermal model of VACV infection to compare pathogenesis of wild-type virus (vv-VCPwt) and a virus lacking VCP (vv-VCPko). vv-VCPko formed smaller lesions in wild-type mice but not in complement-deficient mice. Attenuation of vv-VCPko correlated with increased accumulation of T cells at the site of infection, enhanced neutralizing antibody responses, and reduced viral titers. Importantly, depleting CD8(+) T cells together with CD4(+) T cells, which also eliminated T helper cell-dependent Ab responses, restored vv-VCPko to wild-type levels of virulence. These results suggest that VCP contributes to virulence by dampening both antibody and T cell responses. This work provides insight into how modulation of complement by poxviruses contributes to virulence and demonstrates that a pathogen-encoded complement regulatory protein can modulate adaptive immunity.

CD8 T cells producing IL-17 and IFN-gamma initiate the innate immune response required for responses to antigen skin challenge

Effector CD8 T cell recruitment into the skin in response to Ag challenge requires prior CXCL1/KC-directed neutrophil infiltration. Mechanisms inducing CXCL1 production and the dynamics of neutrophil-CD8 T cell interactions during elicitation of Ag-specific responses in the skin were investigated. CXCL1 and CXCL2/MIP-2 were produced within 3-6 h of Ag challenge at 10-fold higher levels in skin challenge sites of Ag-sensitized vs nonsensitized mice. In the challenge sites of sensitized mice this production decreased at 6-9 h postchallenge to near the levels observed in skin challenge sites of nonsensitized mice but rose to a second peak 12 h after challenge. The elevated early neutrophil chemoattractant production at 3-6 h after skin challenge of sensitized animals required both IFN-gamma and IL-17, produced by distinct populations of Ag-primed CD8 T cells in response to Ag challenge. Although induced by the Ag-primed CD8 T cells, the early CXCL1 and CXCL2 production was accompanied by neutrophil but not CD8 T cell infiltration into the skin Ag challenge site. Infiltration of the CD8 T cells into the challenge site was not observed until 18-24 h after challenge. These results demonstrate an intricate series of early interactions between Ag-specific and innate immune components that regulate the sequential infiltration of neutrophils and then effector T cells into the skin to mediate an immune response.

Antimicrobial effects of interferon-inducible CXC chemokines against Bacillus anthracis spores and bacilli

Based on previous studies showing that host chemokines exert antimicrobial activities against bacteria, we sought to determine whether the interferon-inducible Glu-Leu-Arg-negative CXC chemokines CXCL9, CXCL10, and CXCL11 exhibit antimicrobial activities against Bacillus anthracis. In vitro analysis demonstrated that all three CXC chemokines exerted direct antimicrobial effects against B. anthracis spores and bacilli including marked reductions in spore and bacillus viability as determined using a fluorometric assay of bacterial viability and CFU determinations. Electron microscopy studies revealed that CXCL10-treated spores failed to undergo germination as judged by an absence of cytological changes in spore structure that occur during the process of germination. Immunogold labeling of CXCL10-treated spores demonstrated that the chemokine was located internal to the exosporium in association primarily with the spore coat and its interface with the cortex. To begin examining the potential biological relevance of chemokine-mediated antimicrobial activity, we used a murine model of inhalational anthrax. Upon spore challenge, the lungs of C57BL/6 mice (resistant to inhalational B. anthracis infection) had significantly higher levels of CXCL9, CXCL10, and CXCL11 than did the lungs of A/J mice (highly susceptible to infection). Increased CXC chemokine levels were associated with significantly reduced levels of spore germination within the lungs as determined by in vivo imaging. Taken together, our data demonstrate a novel antimicrobial role for host chemokines against B. anthracis that provides unique insight into host defense against inhalational anthrax; these data also support the notion for an innovative approach in treating B. anthracis infection as well as infections caused by other spore-forming organisms.

Multichannel fluorescence spinning disk microscopy reveals early endogenous CD4 T cell recruitment in contact sensitivity via complement

Contact sensitivity (CS) is one of the primary in vivo models of T cell-mediated inflammation. The presence of CS-initiating CD4 T lymphocytes at the time of challenge is essential for transfer and full development of the late phase CS inflammatory response. From this observation investigators have speculated that early recruitment of CD4 T cells to the site of challenge must occur. Moreover, there must be rapid synthesis/release and disappearance of an important mediator during the first hours after hapten challenge. Using spinning disk confocal microscopy, we observed the very early effector events of the immune response. Simultaneous, real-time visualization of predominant neutrophil and extremely rare CD4 T cell trafficking in the challenged skin vasculature was noted (one rolling CD4 T cell for every 10-18 rolling and adherent neutrophils). We demonstrate that neutrophil adhesion during the early CS response was reduced in C5a receptor-deficient (C5aR-/-) mice or leukotriene B4 receptor antagonist-treated mice, whereas CD4 T cell recruitment was only inhibited in C5aR-/- mice. In line with these observations, leukocyte infiltration and the associated tissue damage were significantly reduced in C5aR-/- mice but not in leukotriene B4 receptor antagonist-treated wild-type mice 24 h after challenge. C5a receptor expression on T cells and not on tissue resident cells was important for the development of a CS response. Thus, by using spinning disk confocal microscopy we visualized the early events of an adaptive immune response and identified the rare but essential recruitment of CD4 T cells via the complement pathway.

Th-17, monokines, collagen type V, and primary graft dysfunction in lung transplantation

RATIONALE

The pathogenesis of primary graft dysfunction (PGD), a serious complication of lung transplantation, is poorly understood. Human studies and rodent models have shown that collagen type V (col[V]), stimulates IL-17-dependent cellular immunity after lung transplantation.

OBJECTIVES

To determine whether patients with end-stage lung disease develop pretransplant col(V)-specific cellular immunity, and if so, the impact of this response on PGD.

METHODS

Trans-vivo delayed-type hypersensitivity (TV-DTH) assays were used to evaluate memory T-cell responses to col(V) in 55 patients awaiting lung transplantation. Pa(O(2))/Fi(O(2)) index data were used to assess PGD. Univariate risk factor analysis was performed to identify variables associated with PGD. Rats immunized with col(V) or irrelevant antigen underwent lung isografting to determine if prior anti-col(V) immunity triggers PGD in the absence of alloreactivity.

MEASUREMENTS AND MAIN RESULTS

We found that 58.8% (10/17) of patients with idiopathic pulmonary fibrosis, and 15.8% (6/38) of patients without idiopathic pulmonary fibrosis tested while on the wait list for a lung transplant were col(V) DTH positive. Col(V) reactivity was CD4(+) T-cell and monocyte mediated, and dependent on IL-17, IL-1beta, and tumor necrosis factor (TNF)-alpha. Pa(O(2))/Fi(O(2)) indices were impaired significantly 6-72 hours after transplantation in col(V)-reactive versus nonreactive patients. Univariate risk factor analysis identified only preoperative TV-DTH to col(V) and ischemic time as predictors of PGD. Finally, in a rat lung isograft model, col(V) sensitization resulted in significantly lower Pa(O(2))/Fi(O(2)), increased local TNF-alpha and IL-1beta production, and a moderate-to-severe bronchiolitis/vasculitis when compared with control isografts.

CONCLUSIONS

The data suggest that activation of innate immunity by col(V)-specific Th-17 memory cells represents a novel pathway to PGD after lung transplantation.

Contact Dermatitis

Contact dermatitis is a common skin disease caused by contact with irritants or allergens. Irritant contact dermatitis is a result of nonspecific irritant factors, which cause activation of mainly innate immunity, resulting in skin inflammation. Contact hypersensitivity, which manifests itself as allergic contact dermatitis, is result of adaptive immune response, where sensitization to hapten-carrier complexes leads to T-cell-mediated contact allergy. Subsequent contact with the hapten results in skin inflammation. This review concentrates on the role of cutaneous receptors in contact dermatitis and highlights potential targets for treatment interventions.

UV radiation-induced immunosuppression is greater in men and prevented by topical nicotinamide

UV radiation-induced immunosuppression augments cutaneous carcinogenesis. The incidence of skin cancer continues to increase despite increased use of sunscreens, which are less effective at preventing immunosuppression than sunburn. Using the Mantoux reaction as a model of skin immunity, we investigated the effects of solar-simulated (ss) UV and its component UVA and UVB wavebands and tested the ability of topical nicotinamide to protect from UV-induced immunosuppression. Healthy, Mantoux-positive volunteers were UV-irradiated on their backs, with 5% nicotinamide or vehicle applied to different sites in a randomized, double-blinded manner. Subsequent Mantoux testing at irradiated and adjacent unirradiated sites enabled measurement of UV-induced immunosuppression with and without nicotinamide. Suberythemal ssUV caused significant immunosuppression, although component UVB and UVA doses delivered independently did not. Men were immunosuppressed by ssUV doses three times lower than those required to immunosuppress women. This may be an important cause of the higher skin cancer incidence and mortality observed in men. Topical nicotinamide prevented immunosuppression, with gene chip microarrays suggesting that the mechanisms of protection may include alterations in complement, energy metabolism and apoptosis pathways. Nicotinamide is a safe and inexpensive compound that could be added to sunscreens or after-sun lotions to improve protection from immunosuppression. immunosuppression.JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://network.nature.com/group/jidclub

Venom therapy in multiple sclerosis

To date many people with multiple sclerosis (MS) seek complementary and alternative medicines (CAM) to treat their symptoms as an adjunct to conventionally used therapies. Among the common CAM therapies, there is a renewed interest in the therapeutic potential of venoms in MS. The efficacy of this therapeutic method remains unclear. However, venom-based therapy using bee, snakes and scorpions venom and/or sea anemones toxin has been recently developed because current investigations have identified the various components and molecular mechanism of the effects of venoms under in vitro and in vivo conditions. The aim of this review is to describe the recent findings regarding the role of venoms and their components in treatment of MS disease and that whether venom therapy could be recommended as a complementary treatment or not.

Antibody-enhanced cross-presentation of self antigen breaks T cell tolerance

We have developed a model of autoimmunity to investigate autoantibody-mediated cross-presentation of self antigen. RIP-mOVA mice, expressing OVA in pancreatic beta cells, develop severe autoimmune diabetes when given OT-I cells (OVA-specific CD8(+) T cells) and anti-OVA IgG but not when given T cells alone. Anti-OVA IgG is not directly injurious to the islets but rather enhances cross-presentation of apoptotic islet antigen to the OT-I cells, leading to their differentiation into potent effector cells. Antibody-driven effector T cell activation is dependent on the presence of activating Fc receptors for IgG (FcgammaRs) and cross-priming DCs. As a consequence, diabetes incidence and severity was reduced in mice lacking activating FcgammaRs. An intact complement pathway was also required for disease development, as C3 deficiency was also partially protective. C3-deficient animals exhibited augmented T cell priming overall, indicating a proinflammatory role for complement activation after the T cell priming phase. Thus, we show that autoreactive antibody can potently enhance the activation of effector T cells in response to cross-presented self antigen, thereby contributing to T cell-mediated autoimmunity.

Invariant NKT cells rapidly activated via immunization with diverse contact antigens collaborate in vitro with B-1 cells to initiate contact sensitivity

In cutaneous contact sensitivity there is an early elicited innate cascade of complement, mast cells, and platelets activated via IgM Abs. This response is required to initiate the elicitation of acquired classical contact sensitivity by leading to local recruitment of effector T cells. We recently performed in vivo experiments showing that collaboration is required between innate-like invariant Valpha14+ NKT cells (iNKT) and the innate-like B-1 B cell subset to induce this initiation process. Contact sensitization triggers iNKT cells to produce IL-4 to coactivate the B-1 cells along with specific Ag for production of the initiating IgM Abs. We now describe in vitro collaboration of iNKT and B-1 cells. Normal peritoneal B-1 cells, incubated in vitro with soluble Ag, and with 1-h in vivo immune iNKT cells producing IL-4, are activated to mediate the contact sensitivity-initiation cascade. The three components of this process can be activated by different Ag. Thus, 1-h iNKT cell activation, B-1 cell stimulation, and generation of immune effector T cells can be induced by sensitization with three different Ag to respectively generate IL-4 and Ag-specific IgM Abs, to recruit the Ag-specific effector T cells. These findings have relevance to allergic and autoimmune diseases in which infections can trigger exacerbation of T cell responses to allergens or to autoantigens.

An hour after immunization peritoneal B-1 cells are activated to migrate to lymphoid organs where within 1 day they produce IgM antibodies that initiate elicitation of contact sensitivity

Elicitation of contact sensitivity (CS), a classic example of T cell-mediated immunity, requires Ag-specific IgM Abs to trigger an initiation process. This early process leads to local recruitment of CS-effector T cells after secondary Ag challenge. These Abs are produced by the B-1 subset of B cells within 1 day after primary skin immunization. In this study we report the surprising observation that B-1 cells in the peritoneal cavity are activated as early as 1 h after naive mice are painted with a contact-sensitizing Ag on the skin of the trunk and feet to begin the initiation of CS. B-1 cells in the spleen and draining lymph nodes produce the initiating Abs by 1 day after immunization, when we found increased numbers of Ag-specific IgM Ab-producing cells in these tissues by ELISPOT assay. Importantly, we show that contact-activated peritoneal B-1 cells migrate to these lymphoid tissues and then differentiate into Ag-specific IgM Ab-producing cells, resulting in specific CS-initiating IgM Abs in the serum by 1 day. Furthermore, pertussis toxin, which is known to inhibit signaling via G protein-coupled chemokines, inhibited the migration of contact-activated peritoneal B-1 cells to the lymphoid tissues, probably due to BLR-1 (Burkitt lymphoma receptor-1). These findings indicate that within 1 h after contact skin immunization, B-1 cells in the peritoneal cavity are activated to migrate to the lymphoid tissues by chemokine-dependent mechanisms to produce serum Ag-specific IgM Abs within 1 day after immunization, leading to local recruitment of CS-effector T cells.

TLR-Dependent IL-4 Production by Invariant Vα14+Jα18+ NKT Cells to Initiate Contact Sensitivity In Vivo

LPS stimulated B-1 cell polyclonal in vivo IgM responses depend on IL-4 release by invariant Valpha14+Jalpha18+ NKT (iNKT) cells. The IgM Abs can recruit effector T cells to mediate contact sensitivity. LPS activates the B-1 cell response just 1 day later, and depends on CD1d, iNKT cells, IL-4, TLR4, and MyD88. LPS in vivo and in vitro stimulates rapid preferential production of IL-4 in hepatic iNKT cells within 2 h. TLR4 were demonstrated in iNKT cells by flow cytometry and functional studies. Thus, innate microbial stimulation via TLR can activate iNKT cell and B-1 cell collaboration. The result is polyclonal IgM Ab responses capable of recruiting Ag-specific T cells into tissues. This may be involved in the promotion of autoimmunity by infectious agents.

Lymphocytes from one side of the bovine mammary gland migrate to the contra lateral gland and lymph node tissue

The four quarters of bovine mammary glands are completely separated and two quarters on each side (right or left) are connected to ipsi lateral supra mammary lymph nodes. It is not clear whether cells infused into the cistern of the mammary gland are capable of migrating to lymph nodes or the general circulation. To examine cell migration, a prescapular lymph node was removed from each of two lactating and three non-lactating dairy cows, and isolated lymphocytes were stained with Hoechst 33342. Autologous stained cells were infused into the mammary gland and then activated by intramammary infusion of zymosan-stimulated serum (source of C5a). After 17 h, Escherichia coli J5 bacterin was infused into the contra lateral mammary gland to mimic infection. After 43 h cows were euthanized and tissue samples (mammary quarters, right and left supra mammary, mesenteric, ileocecal and prescapular lymph nodes, liver and spleen) were collected for microscopic examination as well as flow cytometric analysis. Hoechst stained cells were detected not only in infused quarters, but also in contra lateral quarters as well as in both supra mammary lymph nodes. This indicates that cells infused into the mammary gland migrate to contra lateral tissues and supra mammary lymph nodes.

B cells are not required for T cell priming in low zone tolerance to contact allergens and contact hypersensitivity

Low zone tolerance (LZT) to contact allergens is induced by epicutaneous exposure to haptens in subsensitizing doses resulting in an inhibition of contact hypersensitivity (CHS), which, in contrast, occurs after sensitization with immunogenic doses of allergens. Performing the protocol of tolerance induction resulted in robust LZT to allergens in B cell-deficient mice in vivo, indicating that B cells are not required for the induction and effector phase of LZT. However, CHS reactions in vivo were restricted in B cell-deficient mice as compared to wild-type (WT) mice. In contrast, analysis of hapten-specific T cell activation in vitro revealed a strong proliferative response of T cells derived from both WT and B cell-deficient sensitized mice. Similar to WT animals, T cells obtained from tolerized B cell-deficient mice produced a Tc2 cytokine pattern of LZT with high levels of IL-4 and IL-10, whereas sensitization of B cell-deficient mice resulted in the typical Tc1 cytokine profile of CHS. Adoptive transfer of CD8+ effector T cells from tolerized or sensitized B cell-deficient mice induced significant LZT or CHS reactions, respectively, in WT recipients, demonstrating that the development of hapten-specific effector CD8+ T cells of LZT and CHS is independent of B cells.

Airway hyper-reactivity mediated by B-1 cell immunoglobulin M antibody generating complement C5a at 1 day post-immunization in a murine hapten model of non-atopic asthma

Contact skin immunization of mice with reactive hapten antigen and subsequent airway challenge with the same hapten induces immediate airflow obstruction and subsequent airway hyper-reactivity (AHR) to methacholine challenge, which is dependent on B cells but not on T cells. This responsiveness to airway challenge with antigen is elicited as early as 1 day postimmunization and can be adoptively transferred to naïve recipients via 1-day immune cells. Responses are absent in 1-day immune B-cell-deficient JH(-/-) mice and B-1 B-cell-deficient xid male mice, as well as in recipients of 1-day immune cells depleted of cells with the B-1 cell phenotype (CD19(+) B220(+) CD5(+)). As B-1 cells produce immunoglobulin M (IgM), we sought and found significantly increased numbers of anti-hapten IgM-producing cells in the spleen and lymph nodes of 1-day immune wild-type mice, but not in xid mice. Then, we passively immunized naive mice with anti-hapten IgM monoclonal antibody and, following airway hapten challenge of the recipients, we showed both immediate airflow obstruction and AHR. In addition, AHR was absent in complement C5 and C5a receptor-deficient mice. In summary, this study of the very early elicited phase of a hapten asthma model suggests, for the first time, a role of B-1 cells in producing IgM to activate complement to rapidly mediate asthma airway reactivity only 1 day after immunization.

IgE-mediated mast cell activation induces Langerhans cell migration in vivo

Langerhans cells and mast cells are both resident in large numbers in the skin and act as sentinel cells in host defense. The ability of mast cells to induce Langerhans cell migration from the skin to the draining lymph node in vivo was examined. Genetically mast cell-deficient (W/Wv) mice and control mice were sensitized with IgE Ab in the ear pinna. Seven to 14 days later, mice were challenged with Ag i.v. After a further 18-24 h, epidermal sheets and draining auricular lymph nodes were examined using Langerin/CD207 immunostaining. In mast cell-containing mice, a significant decrease in the number of Langerhans cells was observed at epidermal sites of mast cell activation. A significant increase in total cellularity and accumulation of Langerin-positive dendritic cells was observed in the auricular lymph nodes, draining the sites of IgE-mediated mast cell activation. These changes were not observed in W/Wv mice, but were restored by local mast cell reconstitution. Treatment of mast cell-containing mice with the H2 receptor antagonist cimetidine significantly inhibited the observed IgE/Ag-induced changes in Langerhans cell location. In contrast, Langerhans cell migration in response to LPS challenge was not mast cell dependent. These data directly demonstrate the ability of mast cells to induce dendritic cell migration to lymph nodes following IgE-mediated activation in vivo by a histamine-dependent mechanism.

Enhanced apoptosis of peripheral CD5-negative B lymphocytes from chronically hepatitis C virus-infected patients: reversal after antiviral treatment

Whereas enhanced peripheral T-cell apoptosis and its association with autoimmunity have recently been reported, the apoptotic status of peripheral B cells in chronic hepatitis C virus (HCV) infection remains ambiguous. We therefore sought to investigate the sensitivity of peripheral B cells to apoptosis and to assess the possible benefits of antiviral treatment in mitigating these effects. Spontaneous apoptosis, the extent of apoptosis rescue, and NF-kappaB expression in peripheral B cells were studied in patients with chronic HCV infections (group 1), in sustained responders after antiviral treatment (group 2), and in healthy controls (group 3). For group 1, spontaneous B-cell apoptosis was increased (26% +/- 4.6%) and apoptosis rescue was altered (39%) compared to group 3 (18% +/- 5% and 50%, respectively; P = 0.001). In contrast, apoptosis and apoptosis rescue were similar for groups 2 and 3. Enhanced B-cell apoptosis was associated with decreased NF-kappaB expression and was found only in CD5-negative (CD5(neg)) B cells, whereas CD5(pos) cells were apoptosis resistant. Chronic HCV infection is associated with enhanced peripheral B-cell apoptosis and decreased apoptosis rescue. Successful antiviral treatment reverses these abnormalities to the levels seen in healthy individuals. The relative resistance of the CD5(pos) B-cell subpopulation to apoptosis may play a role in HCV-related autoimmunity and lymphoproliferation.

The intensity of neutrophil infiltration controls the number of antigen-primed CD8 T cells recruited into cutaneous antigen challenge sites

Recruitment of antigen-specific T cells into the skin is a critical initiating event during immune responses to many parasites and tumors as well as T cell-mediated, cutaneous, allergic responses and autoimmune diseases. Mechanisms directing T cell trafficking into skin remain largely undefined. Here, we show that cutaneous contact with reactive antigen induces KC/CXC chemokine ligand 1 production and neutrophil infiltration in an antigen, dose-dependent manner. The intensity of neutrophil infiltration into cutaneous antigen challenge sites, in turn, controls the number of antigen-primed T cells recruited into the site and the magnitude of the immune response elicited. The absence of responses in immune animals challenged with suboptimal doses of antigen is overcome by manipulating neutrophil infiltration that then directs antigen-primed T cell infiltration into the challenge site. This inflammation also directs T cells primed to one antigen (dinitrofluorobenzene) into the site when challenged with a completely different antigen (oxazolone). These results identify the intensity of neutrophil infiltration into cutaneous, antigen-deposition sites as a critical parameter for the level of antigen-primed T cell recruitment to mediate the adaptive immune response. This interplay between the innate and adaptive responses suggests a strategy to modulate, in a positive or negative manner, antigen-primed T cell infiltration into cutaneous inflammation sites.

Up-regulation of C5a receptor expression and function on human monocyte derived dendritic cells by prostaglandin E2

The expression of the C5a-receptor (C5aR) on dendritic cells, its regulation and function have not been well established thus far. We show that the C5aR is expressed on human monocyte-derived dendritic cells (DC) and can be down-regulated by maturation stimuli such as tumour necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS) or CD40L and by the T helper 1-cytokine interferon-gamma (INF-gamma). Prostaglandin E2 (PGE2), a proinflammatory mediator supporting dendritic cell activation and necessary for adequate DC migration, leads to the up-regulation of C5aR expression when incubated alone and prevents down-regulation when given in combination with TNF-alpha or LPS. Stimulation of C5aR on DC triggered F-actin polymerization, indicating the chemotactic potential of DC elicited by C5a. C5a induced F-actin polymerization was increased when C5aR was up-regulated by PGE2. Stimulation of DC with C5a resulted in interleukin-10 production which was significantly increased after C5aR up-regulation with TNF-alpha and PGE2. Therefore, up-regulation of the C5aR on human DC alters their chemotactic and immunologic response to C5a.

Cutaneous immunization rapidly activates liver invariant Valpha14 NKT cells stimulating B-1 B cells to initiate T cell recruitment for elicitation of contact sensitivity

T cell recruitment to elicit contact sensitivity (CS) requires a CS-initiating process mediated by B-1 cells that produce IgM, which activates complement to promote T cell passage into the tissues. We now show that Vα14i NKT cells induce B-1 cell activation likely by releasing IL-4 early postimmunization. The CS initiation process is absent in Jα18^−/− and CD1d^−/− NKT cell–deficient mice and is reconstituted by populations enriched for Vα14i NKT cells. Transfers are not effective if cells are derived from IL-4^−/− mice. Staining with specific tetramers directly showed that hepatic Vα14i NKT cells increase by 30 min and nearly double by 2 h postimmunization. Transfer of immune B-1 cells also reconstitutes CS responses in NKT cell–deficient mice. The B-1 cells act downstream of the Vα14i NKT cells to restore CS initiation. In addition, IL-4 given systemically to Jα18^−/− or CD1d^−/− NKT cell–deficient mice reconstitutes elicitation of CS. Further, splenocytes from immune Jα18^−/− mice produce less antigen (Ag)-specific IgM antibodies compared with sensitized WT mice. Together these findings indicate that very early after skin immunization Vα14i NKT cells are stimulated to produce IL-4, which activates B-1 cells to produce Ag-specific IgM, subsequently needed to recruit effector T cells for elicitation of CS responses.

B-1 B Cells Mediate Required Early T Cell Recruitment to Elicit Protein-Induced Delayed-Type Hypersensitivity

We define the initiation of elicited delayed-type hypersensitivity (DTH) as a series of processes leading to local extravascular recruitment of effector T cells. Responses thus have two sequential phases: 1) 2-h peaking initiation required for subsequent recruitment of T cells, and 2) the late classical 24-h component mediated by the recruited T cells. We analyzed DTH initiation to protein Ags induced by intradermal immunization without adjuvants. Ag-spceific initiating cells are present by 1 day in spleen and lymph nodes. Their phenotypes, determined by depletion of cell transfers by mAb and complement, are CD5(+), CD19(+), CD22(+), B220(+), Thy1(+), and Mac1(+), suggesting that they are B-1 B cells. DTH initiation is absent in micro MT B cell and xid B-1 cell deficient mice, is impaired in mice unable to secrete IgM, and is reconstituted with 1 day immune serum, suggesting that early B-1 cell-derived IgM is responsible. Study of complement C5a receptor-deficient mice, anti-C5 mAb neutralization, or mast cell deficiency suggests that DTH initiation depends on complement and mast cells. ELISPOT assay confirmed production of Ag-specific IgM Abs at days 1 and 4 in wild-type mice, but not in B-1 cell-deficient xid mice. We conclude that rapidly activated B-1 cells produce specific IgM Abs which, after local secondary skin challenge, form Ag-Ab complexes that activate complement to generate C5a. This stimulates C5a receptors on mast cells to release vasoactive substances, leading to endothelial activation for the 2-h DTH-initiating response, allowing local recruitment of DTH-effector T cells.

Antiviral treatment down-regulates peripheral B-cell CD81 expression and CD5 expansion in chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is associated with immune-mediated abnormalities and B-cell lymphoproliferation. Recently, CD81 was identified as an HCV receptor on B lymphocytes, providing a mechanism by which B cells are infected and activated by the virus. It has recently been shown that peripheral B-cell CD81 overexpression and CD5(+) subpopulation expansion correlate with HCV viral load and are associated with the development of HCV-related autoimmunity. In the present study, we assessed the effects of combination antiviral therapy (alfa interferon and ribavirin) on peripheral B-cell CD81 expression and CD5 expansion and the presence of autoimmune markers. Peripheral B-cell CD5 expression and the mean fluorescence intensity of CD81 were assessed by flow cytometry before and after treatment in 15 HCV-infected patients, in 10 untreated patients, and in 25 healthy controls. A significant posttreatment decrease in peripheral B-cell CD81 expression and disappearance of CD5(+) B-cell expansion were observed in all nine patients in whom a complete and sustained virological response was achieved (P < 0.01) (comparable to those for healthy controls). The decrease in CD81 overexpression and CD5 expansion in these patients was associated with a decrease and/or disappearance of autoimmune markers. In contrast, in nonresponders overexpression of CD81 and expansion of the CD5(+) B-cell subpopulation were not significantly changed and were comparable to those for untreated patients. In conclusion, antiviral therapy down-regulates peripheral B-cell CD81 expression and the CD5(+) population, either directly or by its effect on HCV RNA load. The overexpression of CD81 and the expansion of the population of CD5(+) peripheral B cells in HCV-infected patients may possibly play a role in the development of HCV-associated autoimmunity and lymphoproliferation.

Tolerance is dependent on complement C3 fragment iC3b binding to antigen-presenting cells

Systemic tolerance can be induced by the introduction of antigen into an immune-privileged site. Here we investigated the role of complement in the induction of tolerance after intraocular injection. We found that the development of antigen-specific tolerance is dependent on a complement activation product. The ligation of the complement C3 activation product iC3b to complement receptor type 3 (the iC3b receptor) on antigen-presenting cells resulted in the sequential production of transforming growth factor-beta2 and interleukin-10, which is essential for the induction of tolerance. These observations may extend to the development of both neonatal tolerance and other forms of acquired tolerance.

Suppression of allergic reaction by lambda-carrageenan: toll-like receptor 4/MyD88-dependent and -independent modulation of immunity

BACKGROUND

Recognition of foreign substances by innate immunity through pattern recognition receptors (PRRs) regulates acquired immunity such as allergic reaction. Because PRRs recognize heterogeneous ligands, daily food intake can potentially regulate immune allergic reaction.

OBJECTIVE

Elucidation of the effect of lambda-carrageenan on allergic reactions was aimed.

METHOD

IFN-gamma and IL-4 was measured in in vitro T cell-stimulated culture. Cytokine production from macrophages in response to lambda-carrageenan was measured as indicator for innate immunity activation. Mice were immunized with OVA in alum to induce specific IgE, and then histamine release was induced by systemic injection of OVA.

RESULTS

Activation of innate immunity by lambda-carrageenan is dependent on Toll-like receptor-4 (TLR4) and MyD88, in which induction of pro-inflammatory cytokines such as TNF-alpha and IL-6 was largely impaired in macrophages from TLR4- and MyD88-deficient mice. Footpad oedema, a model for in vivo inflammatory reactions, was significantly reduced in these mice. Similar to recent evidence showing a preference for the stimulation of Th1 via TLR/MyD88 signalling, lambda-carrageenan showed enhanced IFN-gamma and decreased IL-4 in stimulated T cell cultures. Interestingly, increased IFN-gamma production was still seen in TLR4- and MyD88-deficient splenocytes. Oral administration of lambda-carrageenan to immunized mice successfully decreased OVA-specific IgE, and lambda-carrageenan was also effective in previously immunized mice. Further, serum histamine release upon systemic challenge of OVA was significantly inhibited. Neither OVA-specific IgG1/IgG2a nor cytokine secretion from in vitro cultures were altered, suggesting the involvement of multiple PRRs as demonstrated by TLR4/MyD88-independent IFN-gamma up-regulation. The simultaneous feeding of OVA with lipopolysaccharide abrogated oral tolerance, but lambda-carrageenan was not only devoid of such an effect but was also found to promote oral tolerance in the absence of TLR4.

CONCLUSION

lambda-Carrageenan was suggested to be a useful dietary supplement to ameliorate allergic reactions while maintaining oral tolerance-dependent intestinal homeostasis.

Complement component 3 is required for optimal expansion of CD8 T cells during a systemic viral infection

In addition to its established role in innate immune mechanisms, complement component C3 is also of critical importance in B cell activation and T cell-dependent Ab responses. In this study, we have examined the requirement for C3 in the generation of primary CD8 T cell responses to an acute systemic viral infection. We compared Ag-specific CD8 T cell responses to lymphocytic choriomeningitis virus (LCMV) between wild-type (+/+) and C3-deficient (C3(-/-)) mice on both 129/B6 and B6 backgrounds. These studies revealed that C3 activity is required for optimal expansion of LCMV-specific effector CD8 T cells in an epitope-dependent fashion, which is influenced by the genetic background of the mice. Studies in complement receptor 1/2 (CR1/CR2)-deficient mice showed that regulation of LCMV-specific CD8 T cell responses by C3 is not dependent upon CR1/CR2. These findings may have implications in vaccine development, therapy of autoimmune diseases, and prevention of graft rejection.

B cell-dependent T cell responses: IgM antibodies are required to elicit contact sensitivity

Contact sensitivity (CS) is a classic example of in vivo T cell immunity in which skin sensitization with reactive hapten leads to immunized T cells, which are then recruited locally to mediate antigen-specific inflammation after subsequent skin challenge. We have previously shown that T cell recruitment in CS is triggered by local activation of complement, which generates C5a that triggers C5a receptors most likely on mast cells. Here, we show that B-1 cell-derived antihapten IgM antibodies generated within 1 day (d) of immunization combine with local challenge antigen to activate complement to recruit the T cells. These findings overturn three widely accepted immune response paradigms by showing that (a) specific IgM antibodies are required to initiate CS, which is a classical model of T cell immunity thought exclusively due to T cells, (b) CS priming induces production of specific IgM antibodies within 1 d, although primary antibody responses typically begin by day 4, and (c) B-1 cells produce the 1-d IgM response to CS priming, although these cells generally are thought to be nonresponsive to antigenic stimulation. Coupled with previous evidence, our findings indicate that the elicitation of CS is initiated by rapidly formed IgM antibodies. The IgM and challenge antigen likely form local complexes that activate complement, generating C5a, leading to local vascular activation to recruit the antigen-primed effector T cells that mediate the CS response.

Subunits of IgM reconstitute defective contact sensitivity in B-1 cell-deficient xid mice: kappa light chains recruit T cells independent of complement

The elicitation of contact sensitivity (CS) to local skin challenge with the hapten trinitrophenyl (TNP) chloride requires an early process that is necessary for local recruitment of CS-effector T cells. This is called CS initiation and is due to the B-1 subset of B cells activated at immunization to produce circulating IgM Ab. At challenge, the IgM binds hapten Ag in a complex that locally activates C to generate C5a that aids in T cell recruitment. In this study, we present evidence that CS initiation is indeed mediated by C-activating classic IgM anti-TNP pentamer. We further demonstrate the involvement of IgM subunits derived either from hybridomas or from lymphoid cells of actively immunized mice. Thus, reduced and alkylated anti-TNP IgM also initiates CS, likely due to generated H chain-L chain dimers, as does a mixture of separated H and L chains that still could weakly bind hapten, but could not activate C. Remarkably, anti-TNP kappa L chains alone mediated CS initiation that was C-independent, but was dependent on mast cells. Thus, B-1 cell-mediated CS initiation required for T cell recruitment is due to activation of C by specific IgM pentamer, and also subunits of IgM, while kappa L chains act via another C-independent but mast cell-dependent pathway.

Immunoglobulin-free light chains elicit immediate hypersensitivity-like responses

Immunoglobulin (Ig)-free light chains IgLC are present in serum and their production is augmented under pathological conditions such as multiple sclerosis, rheumatoid arthritis and neurological disorders. Until now, no (patho)physiological function has been ascribed to circulating Ig light chains. Here we show that IgLCs can confer mast cell dependent hypersensitivity in mice. Antigenic stimulation results in plasma extravasation, cutaneous swelling and mast-cell degranulation. We show that IgLCs have a crucial role in development of contact sensitivity, which could be completely prevented by a novel IgLC antagonist. Although IgE and IgG(1) are central to the induction of immediate hypersensitivity reactions, our results show that IgLCs have similar activity. IgLCs may therefore be a novel factor in the humoral immune response to antigen exposure. Our findings open new avenues in investigating the pathogenesis of autoimmune diseases and their treatments.

Peripheral B-cell CD5 expansion and CD81 overexpression and their association with disease severity and autoimmune markers in chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is associated with immune-mediated abnormalities and B-cell lymphoproliferation evolving to an overt lymphoma. Recently, CD81 was identified as an HCV receptor on B-lymphocytes, providing a mechanism by which B cells are infected and activated by the virus. In addition, expansion of CD5+ B lymphocytes was described to be associated with various non-HCV related autoimmune disorders. Therefore, we studied the possible role of peripheral B cells CD81 and CD5 over-expression in the development of HCV-related autoimmunity and their association with disease severity in chronic HCV infection. Peripheral B cells CD5 expression and mean fluorescence intensity (MFI) of CD81 were determined in 30 HCV-infected patients, 30 healthy controls and 15 patients with hepatitis B virus infection using fluorescence-activated cell scan (FACS). We have also investigated the association between peripheral CD5 and CD81 B-cell over-expression and markers of autoimmunity and disease severity in patients chronically infected by HCV. CD5+ B-cells were increased in chronic HCV infection (23.2 +/- 7.2%) compared with those of healthy controls (15 +/- 5.5%) (P < 0.0001) and chronic HBV infection (19 +/- 3.7%) (P = 0.08). CD81 MFI was significantly higher in HCV-infected compared to HBV-infected patients and healthy controls. Both increased CD81 MFI and CD5+ B-cell expansion were associated with the production of rheumatoid factor and mixed cryoglobulins and positively correlated with HCV viral load and histological activity index. The overexpression of CD81 and the expansion of CD5+ peripheral B-cells in HCV-infected patients may possibly play a role in the development of HCV-associated autoimmunity and lymphoproliferation.

Skin inflammation during contact hypersensitivity is mediated by early recruitment of CD8+ T cytotoxic 1 cells inducing keratinocyte apoptosis

Contact hypersensitivity (CHS) is a T cell-mediated, Ag-specific skin inflammation induced by skin exposure to haptens in sensitized individuals. Th1/T cytotoxic 1 cells are effector cells of CHS, whereas Th2/T regulatory CD4(+) T cells have down-regulating properties. We have previously shown that CHS to 2,4-dinitrofluorobenzene is mediated by specific CD8(+) effector cells, whose cytolytic activity is mandatory for induction of skin inflammation. In this study, using immunohistochemistry and RT-PCR analysis, we show that CD8(+) T cells are rapidly recruited into the skin at the site of hapten challenge before the onset of clinical and histological signs of skin inflammation. This early CD8(+) T cell recruitment is concomitant with: 1) transient IFN-gamma mRNA expression suggesting local activation of effector cells; and 2) induction of keratinocyte (KC) apoptosis which gradually increased to a maximum at the peak of the CHS response. Alternatively, skin infiltration of CD4(+) T cells occurred later and coincided with the peak of the CHS reaction and the beginning of the resolution of skin inflammation. Mice deficient in CD8(+) T cells did not develop CHS, whereas mice deficient in CD4(+) T cells developed an enhanced inflammatory response with increased numbers of CD8(+) T cells recruited in the skin associated with massive KC apoptosis. These data show that CHS is due to the early and selective recruitment in the skin of CD8(+) T cytotoxic 1 effector cells responsible for KC apoptosis.

Topical tacrolimus and cyclosporin A differentially inhibit early and late effector phases of cutaneous delayed-type and immunoglobulin E hypersensitivity

Systemic and topical administration routes of tacrolimus and cyclosporin A (CsA) were compared in effects on early and late phases of elicited T-cell-mediated contact sensitivity (CS), and effects on early and late phases of cutaneous immunoglobulin E (IgE) antibody-mediated hypersensitivity responses in mice. Thus, both CS and IgE responses in the skin have an early mast-cell-dependent phase, and also a late inflammatory phase. We measured the effects of both immunosuppressants on both phases of the respective T cell versus IgE responses. Systemic administration of both agents completely suppressed CS and IgE late-phase responses, but failed to affect either early phase. In contrast, when topical CsA was used, low doses abolished the early phase of IgE responses, but even high doses did not inhibit the early phase of CS. Conversely, topical tacrolimus inhibited the early phase of CS more potently than the early phase of cutaneous IgE hypersensitivity responses. Thus, topical treatment was needed to inhibit the early phases and the two agents acted differentially, suggesting differing susceptibility of the early phases, that are probably due to different signalling mechanisms. These studies underscore the potential value of topical administration of these powerful immunosuppressive agents in the treatment of allergic diseases that exhibit features of early-phase mast-cell-dependent inflammation, and late inflammation due to mast cells or to T cells, such as atopic dermatitis or asthma, since the early phase is predominantly susceptible to topical application, while the last phase of both IgE and T-cell inflammation responds to systemic treatment with both agents.

Anaphylatoxins and infectious and non-infectious inflammatory diseases

In recent years a plethora of data has accumulated directing toward an important role of polypeptides C3a and C5a and its degradation product C5adesArg, summarized as anaphylatoxins (ATs), in microbial host defense and immune regulation. The ATs exert their various biologic functions by interacting with specific C3a- and C5a-receptors present on cells of myeloid origin, epithelial cells, smooth muscle cells as well as on activated B- and T-cells. Activation of AT receptors mediates signal transduction pathways triggering a variety of proinflammatory events. However, by interacting with the cytokine- and chemokine network C3a and C5a exhibit also anti-inflammatory properties. In this review the focus is on the pathogenetic role of the ATs in sepsis, immune complex disease, delayed type hypersensitivity and asthma. Discussed are data from animal models in which the ATs are blocked by specific C3a or C5a inhibitors or from mice with genetic deletions of the specific receptors of either C3a or C5a/C5adesArg.

A catechol antioxidant protocatechuic acid potentiates inflammatory leukocyte-derived oxidative stress in mouse skin via a tyrosinase bioactivation pathway

The modifying effects of topical application of a catechol antioxidant protocatechuic acid (PA) on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammatory responses in mouse skin were investigated. Treatment with a high dose (20,000 nmol) of PA, based on time of application, modifies inflammatory responses in the skin of the B6C3F(1) mouse, a resistant strain to inflammatory response induction by TPA, but shows much higher tyrosinase expression than that of an albino mouse. The responsibility of a large amount of PA-induced leukocyte infiltration to an inflamed region in a B6C3F(1) mouse is more sensitive than that of an ICR albino mouse. When ICR mice were treated with TPA (1.6 nmol) twice weekly for 5 weeks to induce chronic inflammatory responses, pretreatment with 1600 nmol PA 30 min prior to each TPA treatment significantly enhanced the inflammatory responses including edema formation, leukocyte infiltration, and the level of thiobarbituric acid-reacting substances. The dose-dependency was closely parallel to the results of a tumor promotion study of PA previously reported. Further, the treatment of PA alone resulted in tyrosinase-dependent contact hypersensitivity in ICR mouse skin. In addition, the in vitro study of cytotoxicity demonstrated that bioactivation by tyrosinase but not myeloperoxidase of PA significantly enhanced cytotoxicity and intracellular glutathione consumption. We conclude that the tyrosinase-derived reactive quinone intermediate(s) of PA, which binds nucleophilic residues of proteins including sulfhydryl group and conjugates of which are recognized as haptens, was partially involved in alteration of the cellular immune functions including oxygen radical-generating leukocytes migration to inflamed regions.