CD22 and CD72 cooperatively contribute to the development of the reverse Arthus reaction model.

BACKGROUND: Local type III hypersensitivity reactions are acute inflammatory events induced by immune complex (IC) deposition. CD22 and CD72 are B cell-specific cell surface molecules that negatively regulate B cell function. OBJECTIVE: To elucidate the roles of CD22 and CD72 in the development of IgG-mediated type III hypersensitivity reactions. METHOD: The reverse Arthus reaction model in the skin was induced in mice lacking CD22 (CD22-/-), CD72 (CD72-/-), and both of them (CD22-/-/CD72-/-). Edema at 4h and hemorrhage at 8h after IC challenge were evaluated. Inflammatory cell infiltration and cytokine and chemokine expression were also examined. RESULTS: Edema and hemorrhage were significantly reduced in CD22-/-/CD72-/- mice compared with wild-type mice. The loss of both membrane proteins resulted in a greater decrease in edema at 4h, but not hemorrhage at 8h, than the loss of each protein alone. Infiltration of neutrophils, macrophages, and T cells, and the expression of TNF-α, IL-6, MIP-1α, and CCR5 mRNA were also diminished in the knockout mice compared to wild-type mice, and most significantly reduced in CD22-/-/CD72-/- mice. Regulatory T (Treg) cells in the spleen were significantly increased in all knockout mice at 4h. Significant differences in the severity of edema and hemorrhage between wild-type and knockout mice were lost when Treg cells were depleted in the knockout mice. CONCLUSION: These results demonstrate that CD22 and CD72 expression contribute to the development of the reverse Arthus reaction model and CD22 and CD72 might be therapeutic targets for human IC-mediated diseases.

Intracapillary immune complexes recruit and activate slan-expressing CD16+ monocytes in human lupus nephritis.

Lupus nephritis is a major cause of morbidity in patients with systemic lupus erythematosus. Among the different types of lupus nephritis, intracapillary immune complex (IC) deposition and accumulation of monocytes are hallmarks of lupus nephritis class III and IV. The relevance of intracapillary ICs in terms of monocyte recruitment and activation, as well as the nature and function of these monocytes are not well understood. For the early focal form of lupus nephritis (class III) we demonstrate a selective accumulation of the proinflammatory population of 6-sulfo LacNAc+ (slan) monocytes (slanMo), which locally expressed TNF-α. Immobilized ICs induced a direct recruitment of slanMo from the microcirculation via interaction with Fc γ receptor IIIA (CD16). Interestingly, intravenous immunoglobulins blocked CD16 and prevented cell recruitment. Engagement of immobilized ICs by slanMo induced the production of neutrophil-attracting chemokine CXCL2 as well as TNF-α, which in a forward feedback loop stimulated endothelial cells to produce the slanMo-recruiting chemokine CX3CL1 (fractalkine). In conclusion, we observed that expression of CD16 equips slanMo with a unique capacity to orchestrate early IC-induced inflammatory responses in glomeruli and identified slanMo as a pathogenic proinflammatory cell type in lupus nephritis.

A novel modified vaccination technique produces IgG antibodies that cause complement-mediated lysis of multiple myeloma cells carrying CD38 antigen.

Objectives were to: 1) induce a lytic IgG antibody (ab) response (via the so called `third vaccination method') against CD38 antigen (ag) residing on the extra-cellular domain of multiple myeloma (MM) cells in recipient rabbits, by combining the CD38 ag with donor-derived anti-CD38 ag lytic IgG ab into an immune complex (IC); and 2) determine whether abs produced would cause complement-mediated lysis (in vitro) of human MM cells containing CD38 ag. The vaccine was created in a two-step process. First, ab (rabbit anti-CD38 ag IgG ab) was raised in donor rabbits by injections of low molecular weight soluble CD38 ag in Freund's complete adjuvant (FCA) and aqueous solution. Second, transfer of pathogenic lytic IgG ab response into recipient rabbits was achieved by injections of ICs composed of CD38 ag and homologous anti-CD38 ag IgG ab. Consequently, recipient rabbits produced the same ab with the same specificity against the target ag as was present in the inoculum, namely agglutinating, precipitating and lytic (as demonstrated in vitro). In an in vitro study, in the presence of complement, donor and recipient rabbits' immune sera caused lysis of CD38 ag associated human MM cells. The most effective lytic ab response causing sera were those from donor rabbits injected with CD38 ag in FCA and those from rabbits injected with ICs, especially when they were administered in adjuvants. These results provided proof of concept that the third vaccination method has good potential as a stand-alone and efficacious method of controlling cancer.

Novel vaccination approach for dengue infection based on recombinant immune complex universal platform.

Dengue infection is on the rise in many endemic areas of the tropics. Vaccination remains the most realistic strategy for prevention of this potentially fatal viral disease but there is currently no effective vaccine that could protect against all four known serotypes of the dengue virus. This study describes the generation and testing of a novel vaccination approach against dengue based on recombinant immune complexes (RIC). We modelled the dengue RIC on the existing Ebola RIC (Phoolcharoen, et al. Proc Natl Acad Sci USA 2011;108(Dec (51)):20695) but with a key modification that allowed formation of a universal RIC platform that can be easily adapted for use for other pathogens. This was achieved by retaining only the binding epitope of the 6D8 ant-Ebola mAb, which was then fused to the consensus dengue E3 domain (cEDIII), resulting in a hybrid dengue-Ebola RIC (DERIC). We expressed human and mouse versions of these molecules in tobacco plants using a geminivirus-based expression system. Following purification from the plant extracts by protein G affinity chromatography, DERIC bound to C1q component of complement, thus confirming functionality. Importantly, following immunization of mice, DERIC induced a potent, virus-neutralizing anti-cEDIII humoral immune response without exogenous adjuvants. We conclude that these self-adjuvanting immunogens have the potential to be developed as a novel vaccine candidate for dengue infection, and provide the basis for a universal RIC platform for use with other antigens.

Immunological complex for enhancement of innate immune response in passive vaccination.

Passive vaccination is used to treat a wide range of infections and cancer. However, this approach has some limitations. An immune complex termed Y-complex was developed to intensify the effect of the passive vaccine. The complex is composed of a microbead that carries specific antibodies and an inducer. It enables targeting of pathogen or abnormal cells, and stimulation of a desired response by innate immune cells, depending on the inducer. The production and efficacy of Y-complex as a passive immune prophylaxis is demonstrated in this study by its use in treating cow mastitis. In an in vitro assay, Y-complex inhibited propagation and induced phagocytosis of bacteria. In challenge experiments, cows were inoculated through the udder with Escherichia coli or Streptococcus dysgalactiae. Following treatment with Y-complex, no bacteria were isolated in the milk and N-acetyl-ß-D-glucosaminidase activity had returned to normal levels. Thus the Y-complex approach can be used as an effective treatment for mastitis. Due to its modularity, this approach may serve as a treatment for a variety of disease agents.

Recombinant glycoprotein B vaccine formulation with Toll-like receptor 9 agonist and immune-stimulating complex induces specific immunity against multiple strains of cytomegalovirus.

Natural human cytomegalovirus (CMV) infection is characterized by a strain-specific neutralizing antibody response. This is particularly relevant in clinical settings such as transplantation and pregnancy where reinfection with heterologous strains occurs and the immune system does not mount an effective response against the infecting strain due to underlying immunosuppression. There is an emerging argument that a CMV vaccine that induces high titres of cross-neutralizing antibodies will be more effective in protecting individuals from infection with antigenically different CMV strains. In addition, induction of cell-mediated immunity offers the additional advantage of targeting virus-infected cells. This study presents a novel formulation of a CMV vaccine that, by combining recombinant soluble gB protein with a Toll-like receptor 9 agonist (CpG ODN1826) and immune-stimulating complexes (AbISCO 100), was able to elicit strong polyfunctional CMV-specific cellular and cross-neutralizing humoral immune responses. These data demonstrated that prime-boost immunization of human leukocyte antigen (HLA)-A2 mice with gB protein in combination with CpG ODN1826 and AbISCO 100 induced long-lasting CMV-specific CD4(+) and CD8(+) T-cell and humoral responses. Furthermore, these responses neutralized infection with multiple strains of CMV expressing different gB genotypes and afforded protection against challenge with recombinant vaccinia virus encoding the gB protein. These observations argue that this novel vaccine strategy, if applied to humans, should facilitate the generation of a robust, pluripotent immune response, which may be more effective in preventing infection with multiple strains of CMV.

Anti-CD40L immune complexes potently activate platelets in vitro and cause thrombosis in FCGR2A transgenic mice.

Anti-CD40L immunotherapy in systemic lupus erythematosus patients was associated with thromboembolism of unknown cause. We previously showed that monoclonal anti-CD40L immune complexes (ICs) activated platelets in vitro via the IgG receptor (FcgammaRIIa). In this study, we examined the prothrombotic effects of anti-CD40L ICs in vivo. Because mouse platelets lack FcgammaRIIa, we used FCGR2A transgenic mice. FCGR2A mice were injected i.v. with preformed ICs consisting of either anti-human CD40L mAb (M90) plus human CD40L, or a chimerized anti-mouse CD40L mAb (hMR1) plus mouse CD40L. ICs containing an aglycosylated form of hMR1, which does not bind FcgammaRIIa, were also injected. M90 IC caused shock and thrombocytopenia in FCGR2A but not in wild-type mice. Animals injected with hMR1 IC also experienced these effects, whereas those injected with aglycosylated-hMR1 IC did not, demonstrating that anti-CD40L IC-induced platelet activation in vivo is FcgammaRIIa-dependent. Sequential injections of individual IC components caused similar effects, suggesting that ICs were able to assemble in circulation. Analysis of IC-injected mice revealed pulmonary thrombi consisting of platelet aggregates and fibrin. Mice pretreated with a thrombin inhibitor became moderately thrombocytopenic in response to anti-CD40L ICs and had pulmonary platelet-thrombi devoid of fibrin. In conclusion, we have shown for the first time that anti-CD40L IC-induced thrombosis can be replicated in mice transgenic for FcgammaRIIa. This molecular mechanism may be important for understanding thrombosis associated with CD40L immunotherapy. The FCGR2A mouse model may also be useful for assessing the hemostatic safety of other therapeutic Abs.

Improved IL-2 immunotherapy by selective stimulation of IL-2 receptors on lymphocytes and endothelial cells.

IL-2 immunotherapy is an attractive treatment option for certain metastatic cancers. However, administration of IL-2 to patients can lead, by ill-defined mechanisms, to toxic adverse effects including severe pulmonary edema. Here, we show that IL-2-induced pulmonary edema is caused by direct interaction of IL-2 with functional IL-2 receptors (IL-2R) on lung endothelial cells in vivo. Treatment of mice with high-dose IL-2 led to efficient expansion of effector immune cells expressing high levels of IL-2Rbetagamma, including CD8(+) T cells and natural killer cells, which resulted in a considerable antitumor response against s.c. and pulmonary B16 melanoma nodules. However, high-dose IL-2 treatment also affected immune cell lineage marker-negative CD31(+) pulmonary endothelial cells via binding to functional alphabetagamma IL-2Rs, expressed at low to intermediate levels on these cells, thus causing pulmonary edema. Notably, IL-2-mediated pulmonary edema was abrogated by a blocking antibody to IL-2Ralpha (CD25), genetic disruption of CD25, or the use of IL-2Rbetagamma-directed IL-2/anti-IL-2 antibody complexes, thereby interfering with IL-2 binding to IL-2Ralphabetagamma(+) pulmonary endothelial cells. Moreover, IL-2/anti-IL-2 antibody complexes led to vigorous activation of IL-2Rbetagamma(+) effector immune cells, which generated a dramatic antitumor response. Thus, IL-2/anti-IL-2 antibody complexes might improve current strategies of IL-2-based tumor immunotherapy.

T-independent antibody responses to T-dependent antigens: a novel follicular dendritic cell-dependent activity.

Follicular dendritic cells (FDCs) periodically arrange membrane-bound immune complexes (ICs) of T-dependent Ags 200-500A apart, and in addition to Ag, they provide B cells with costimulatory signals. This prompted the hypothesis that Ag in FDC-ICs can simultaneously cross-link multiple BCRs and induce T cell-independent (TI) B cell activation. TI responses are characterized by rapid IgM production. OVA-IC-bearing FDCs induced OVA-specific IgM in anti-Thy-1-pretreated nude mice and by purified murine and human B cells in vitro within just 48 h. Moreover, nude mice immunized with OVA-ICs exhibited well-developed GL-7(+) germinal centers with IC-retaining FDC-reticula and Blimp-1(+) plasmablasts within 48 h. In contrast, FDCs with unbound-OVA, which would have free access to BCRs, induced no germinal centers, plasmablasts, or IgM. Engagement of BCRs with rat-anti-mouse IgD (clone 11-26) does not activate B cells even when cross-linked. However, B cells were activated when anti-IgD-ICs, formed with Fc-specific rabbit anti-rat IgG, were loaded on FDCs. B cell activation was indicated by high phosphotyrosine levels in caps and patches, expression of GL-7 and Blimp-1, and B cell proliferation within 48 h after stimulation with IC-bearing FDCs. Moreover, anti-IgD-IC-loaded FDCs induced strong polyclonal IgM responses within 48 h. Blockade of FDC-FcgammaRIIB inhibited the ability of FDC-ICs to induce T-independent IgM responses. Similarly, neutralizing FDC-C4BP or -BAFF, to minimize these FDC-costimulatory signals, also inhibited this FDC-dependent IgM response. This is the first report of FDC-dependent but TI responses to T cell-dependent Ags.

Type II-activated macrophages suppress the development of experimental autoimmune encephalomyelitis.

Treatment with immune complexes, which ligate Fcgamma receptors (FcgammaRs), suppresses the development of experimental autoimmune encephalomyelitis (EAE). To determine the mechanism of action, we investigated how these immune complexes affected type II activation of macrophages (that is, exposure to immune complexes in a proinflammatory environment). Our results show that lower doses of interferon-gamma (IFN-gamma) were more effective at priming bone marrow-derived macrophages (BMMphi) to produce more interleukin 10 (IL-10) and less IL-12p40 in response to lipopolysaccharide (LPS) and immune complexes compared with LPS alone. Moreover, at the lowest level of IFN-gamma (20 U ml(-1)), a significant downregulation in the surface expression of CD40, CD80 and PD-L1 was observed in LPS and immune complex-stimulated macrophages (that is, type II activated) than macrophages stimulated with LPS alone (that is, classically activated). Finally, treatment of mice with type II-activated macrophages protected them from developing EAE, suggesting that administration of immune complexes is protective against EAE by inducing type II-activated macrophages.

Adenoviral-mediated overexpression of SOCS3 enhances IgG immune complex-induced acute lung injury.

The lung inflammatory response caused by intratracheal deposition of IgG immune complexes (IC) includes the production of IL-6, which signals through activation of STAT transcription factors. Recently, suppressor of cytokine signaling 3 (SOCS3) has been shown to be a key negative regulator of IL-6/gp130/Jak/STAT3 signal transduction. Although SOCS3 has been implicated in several inflammatory diseases, very little is known regarding its activation and its function in the lung during acute inflammation. Our previous study showed that IL-6/STAT3 activation was triggered in lungs after intrapulmonary deposition of IgG IC in rats. In the current study, we sought to determine whether SOCS3 is playing a regulatory role in the lung inflammatory response. SOCS3 induction occurred during development of inflammation in the IgG IC model of lung injury. Overexpression of SOCS3 in lung using a recombinant adenovirus encoding murine SOCS3 resulted in substantial increases in lung vascular permeability and lung myeloperoxidase, together with enhanced levels of TNF-alpha, MIP-2, and keratinocyte-activated cytokine in bronchoalveolar lavage fluids. SOCS3 overexpression in lungs led to overproduction of bronchoalveolar lavage IL-6, but not IL-10, in this inflammatory model. We further show that activation of STAT3 was inhibited by SOCS3 overexpression as well as by anti-IL-6 treatment during IgG IC-induced lung injury, as determined by EMSA. In vitro, SOCS3 overexpression abrogated IL-6-induced activation of STAT3 in lung epithelial cells. These findings suggest SOCS3 is an important regulator of lung inflammatory injury after deposition of IgG IC.

Immune complex-loaded dendritic cells are superior to soluble immune complexes as antitumor vaccine.

Dendritic cells (DCs) play an important role in the induction of T cell responses. Fc gammaRs, expressed on DCs, facilitate the uptake of complexed Ag, resulting in efficient MHC class I and MHC class II Ag presentation and DC maturation. In the present study, we show that prophylactic immunization with DCs loaded with Ag-IgG immune complexes (ICs) leads to efficient induction of tumor protection in mice. Therapeutic vaccinations strongly delay tumor growth or even prevent tumors from growing out. By depleting CD4+ and CD8+ cell populations before tumor challenge, we identify CD8+ cells as the main effector cells involved in tumor eradication. Importantly, we show that DCs that are preloaded in vitro with ICs are at least 1000-fold more potent than ICs injected directly into mice or DCs loaded with the same amount of noncomplexed protein. The contribution of individual Fc gammaRs to Ag presentation, T cell response induction, and induction of tumor protection was assessed. We show that Fc gammaRI and Fc gammaRIII are capable of enhancing MHC class I-restricted Ag presentation to CD8+ T cells in vitro and that these activating Fc gammaRs on DCs are required for efficient priming of Ag-specific CD8+ cells in vivo and induction of tumor protection. These findings show that targeting ICs via the activating Fc gammaRs to DCs in vitro is superior to direct IC vaccination to induce protective tumor immunity in vivo.

[Immune complex induced rat liver fibrosis model by intraperitoneal injection of human serum albumin].

BACKGROUND: To establish an immune complex induced rat liver fibrosis model by intraperitoneal injection of human serum albumin (HSA). METHODS: Male Wistar rats, weighting 110-120 g, were sensitized with HSA by subcutaneous injections at different sites for 4 shots at intervals of 14, 10 and 10 days. Ten days after the fourth injection, the peritoneal booster dose of HSA was administrated to rats twice weekly for 8 weeks with an initial dose of 5 mg, and progressive increase to 20 mg. Liver biopsy was performed at the beginning of HSA booster, 15, 30, 60 days after HSA booster, and 30, 60, 90, 120 days after discontinuation of HSA booster, respectively. Liver samples were examined for histological changes and liver hydroxyproline (HyP) was measured by biochemical method. Fibrosis serum markers hyaluronate acid (HA) and laminin (LN) were determined by RIA method. RESULTS: After intraperitoneal administration of HSA, the degree of liver pathological changes, the liver Hyp content and serum HA and LN increased (P<0.05). The longer the HSA administrated, the higher the liver pathological change degree (P<0.05) and the levels of liver Hyp and serum HA (P<0.01). After discontinuation of HSA, the levels of serum HA and liver Hyp decreased significantly (P<0.01) but were still significantly higher than those in the controls (P<0.01). The liver fibrosis formation rate was 100% and the fibrosis lasted more than 120 days. CONCLUSION: Intraperitoneal administration of HSA to make rat immune complex induced liver fibrosis model is convenient with high liver fibrosis formation rate and long fibrosis lasting time. The model may be used to evaluate the therapeutic effect of antifibrotic drugs.

Potential use of IL-2/anti-IL-2 antibody immune complexes for the treatment of cancer and autoimmune disease.

Initially discovered as a potent T cell proliferation factor, IL-2 was soon used for cancer immunotherapy, especially for metastatic melanoma and renal cell carcinoma; however, the severe side effects of IL-2 therapy, plus the negative role of IL-2 in maintaining of CD4+ CD25+ T regulatory cells (Tregs), has somewhat dampened enthusiasm for using IL-2 in immunotherapy. This opinion article discusses the possibility of combining IL-2 with certain anti-IL-2 antibodies for reducing the dose of IL-2 needed and preferentially stimulating effector T cells, but not Tregs, an approach that might provide an improved strategy for anticancer immunotherapy. Alternatively, complexes of IL-2 with other anti-IL-2 antibodies can selectively stimulate Tregs and could, therefore, be useful for treating autoimmune diseases.

IgE enhances antibody and T cell responses in vivo via CD23+ B cells.

IgE Abs, passively administered together with their specific Ag, can enhance the production of Abs recognizing this Ag by >100-fold. IgE-mediated feedback enhancement requires the low affinity receptor for IgE, CD23. One possible mechanism is that B cells take up IgE-Ag via CD23 and efficiently present Ag to Th cells, resulting in better Ab responses. To test whether IgE Abs have an effect on Th cells in vivo, mice were adoptively transferred with CD4+ T cells expressing a transgenic OVA-specific TCR, before immunization with IgE anti-TNP (2,4,6-trinitrophenyl) plus OVA-TNP or with OVA-TNP alone. IgE induced a 6- to 21-fold increase in the number of OVA-specific T cells. These cells acquired an activated phenotype and were visible in splenic T cell zones. The T cell response peaked 3 days after immunization and preceded the OVA-specific Ab response by a few days. Transfer of CD23+ B cells to CD23-deficient mice rescued their ability to respond to IgE-Ag. Interestingly, in this situation also CD23-negative B cells produce enhanced levels of OVA-specific Abs. The data are compatible with the Ag presentation model and suggest that B cells can take up Ag via "unspecific" receptors and activate naive T cells in vivo.

A role for the lymphotoxin/LIGHT axis in the pathogenesis of murine collagen-induced arthritis.

A lymphotoxin-beta (LTbeta) receptor-Ig fusion protein (LTbetaR-Ig) was used to evaluate the importance of the lymphotoxin/LIGHT axis in the development and perpetuation of arthritis. Prophylactic treatment with the inhibitor protein LTbetaR-Ig blocked the induction of collagen-induced arthritis in mice and adjuvant arthritis in Lewis rats. Treatment of mice with established collagen-induced arthritis reduced the severity of arthritic symptoms and joint tissue damage. However, in a passive model of anti-collagen Ab-triggered arthritis, joint inflammation was not affected by LTbetaR-Ig treatment precluding LT/LIGHT involvement in the very terminal immune complex/complement/FcR-mediated effector phase. Collagen-II and Mycobacterium-specific T cell responses were not impaired, yet there was evidence that the overall response to the mycobacterium was blunted. Serum titers of anti-collagen-II Abs were reduced especially during the late phase of disease. Treatment with LTbetaR-Ig ablated follicular dendritic cell networks in the draining lymph nodes, suggesting that impaired class switching and affinity maturation may have led to a decreased level of pathological autoantibodies. These data are consistent with a model in which the LT/LIGHT axis controls microenvironments in the draining lymph nodes. These environments are critical in shaping the adjuvant-driven initiating events that impact the subsequent quality of the anti-collagen response in the later phases. Consequently, blockade of the LT/LIGHT axis may represent a novel approach to the treatment of autoimmune diseases such as rheumatoid arthritis that involve both T cell and Ab components.

IgG2a-mediated enhancement of antibody responses is dependent on FcRgamma+ bone marrow-derived cells.

Antibodies (Ab) administered in complex with antigens (Ag) have the capacity to regulate the out-coming specific immune response. Primary immunization with complexes of bovine serum albumin-2,4,6-trinitrophenyl (BSA-TNP) and immunoglobulin (Ig)G2a anti-TNP induced a significant enhancement of IgG1 and IgG2a BSA-specific Ab response compared to immunization with the Ag alone. Enhancement was absent in nude mice, demonstrating the requirement of T cells for this regulation. Secondary immunization with BSA alone in mice previously primed with BSA-TNP/IgG2a led to a dramatic increase of Ab production, showing that immune complexes are efficient inducers of immunological memory. IgG-mediated enhancement of Ab responses has previously been shown to be impaired in mice lacking FcgammaRI, FcgammaRIII and FcepsilonRI owing to gene targeting of the common FcRgamma subunit (FcRgamma-/-). Here we show that enhancement after immunization with BSA-TNP/IgG2a complexes is restored in irradiated FcRgamma-/- recipients transferred with wild-type (FcRgamma+/+) bone marrow (BM) cells. In contrast, no enhancement is seen in FcRgamma+/+ irradiated animals reconstituted with FcRgamma-/- BM cells. We conclude that IgG2a-mediated enhancement of Ab responses is dependent on the presence of FcgammaRI and/or FcgammaRIII on BM-derived cells and that the presence of these receptors on the radioresistant follicular dendritic cell is not essential.

Regulation of experimental lung inflammation.

Acute lung inflammation is an important component of a number of pulmonary diseases, including acute respiratory distress syndrome (ARDS). Much has been learned about the manner in which various insults to lung, such as infection or trauma, bring about recruitment of neutrophils into alveoli and small airways, resulting in parenchymal damage and organ dysfunction. In this brief review, we discuss the endogenous mechanisms in which the lung regulates the acute inflammatory response in rats to intrapulmonary deposition of IgG immune complexes. Emphasis is given to the participation of the transcription factor, NF-kappaB, in the development of lung injury and the endogenous mediators which attempt to control the extent of lung inflammation by modulating the activation of NF-kappaB.

Fc gamma RIII-mediated production of TNF-alpha induces immune complex alveolitis independently of CXC chemokine generation.

We recently demonstrated a codominant role of C5aR and FcgammaRIII in the initiation of IgG immune complex-mediated inflammation in mice. In this study, we investigated the relative contribution of FcgammaRIII in the generation of several cytokines during experimental hypersensitivity pneumonitis/alveolitis in vivo. Induction of immune complex-alveolitis in C57BL/6 mice resulted in strong accumulation of neutrophils into the lung and enhanced chemotactic activity within bronchoalveolar lavage fluid accompanied by an increased production of the proinflammatory cytokines TNF-alpha and IL-1beta as well as the ELR-CXC chemokines macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (KC). FcgammaRIII-deficient C57BL/6 mice (FcgammaRIII(-/-)) showed a marked reduction of the inflammatory response due to decreased production of TNF-alpha, IL-1beta, and MIP-2. Results obtained in C57BL/6 mice either lacking the TNF-alpha class I receptor (TNF-alphaRI(-/-)) or treated with neutralizing anti-TNF-alpha mAb demonstrated an essential contribution of TNF-alpha for mediating IL-1beta release, neutrophil influx, and hemorrhage. Surprisingly, MIP-2 and KC chemokine levels remained largely unaffected in TNF-alphaRI(-/-) mice or after functional inhibition of TNF-alpha. These data suggest that in immune complex alveolitis, the activation of FcgammaRIII may induce divergent downstream effector pathways with TNF-alpha acting independently of CXC chemokines to trigger the inflammatory response in C57BL/6 mice.