Adenosine induces IL-31 secretion by T-helper 2 cells: Implication for the effect of adenosine on atopic dermatitis and its therapeutic strategy.

Interleukin (IL)-31 is a recently-identified cytokine with a well-defined role in the pathogenesis of pruritus. Previously, we reported that adenosine upregulates IL-17A secretion by T-helper (Th)17 cells; however, the effect of adenosine on T cell subsets other than Th17 remains unclear. In this report, we show that adenosine upregulated production of IL-31 by cluster of differentiation (CD)4+ T cells. IL-31 was also upregulated by administration of an adenosine A2a receptor (A2aR) agonist (PSB0777), and adenosine-mediated IL-31 production was inhibited by an A2aR antagonist (istradefylline). Production of Th2-related cytokines (IL-4, IL-10, and IL-13) by CD4+ T cells showed the same tendency. Immune subset analyses revealed that adenosine upregulated IL-31 secretion by CD4+ chemokine receptor 3high T cells, and that Th2 cells differentiated from naïve CD4+ T cells. Administration of istradefylline to mice with atopic dermatitis suppressed the symptoms, suggesting that A2aR antagonists are an effective treatment for inflammatory dermatitis. Taken together, the results indicate that adenosine upregulates secretion of Th2-related cytokines by effector T cells in the skin, thereby triggering atopic dermatitis and associated pruritus.

TAFRO syndrome with a fatal clinical course following BNT162b2 mRNA (Pfizer-BioNTech) COVID-19 vaccination: A case report.

TAFRO syndrome is a rare disorder that manifests as thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. Although this disease often follows a severe clinical course, the cause remains unknown. The coronavirus disease 2019 (COVID-19) pandemic is a major global problem. Vaccination against COVID-19 has been successful; however, there are concerns about severe adverse events. Herein, we report a rare presentation of TAFRO syndrome triggered by the COVID-19 vaccine with a fatal clinical course. A 42-year-old Japanese man presented to our hospital complaining of fever lasting for 2 weeks that occurred a day after receiving the BNT162b2 mRNA (Pfizer-BioNTech) COVID-19 vaccine. The patient had a low platelet count, ascites, reticulin myelofibrosis, renal failure, and lymphadenopathy and was diagnosed with TAFRO syndrome. Despite administering several immunosuppressive drugs, the condition did not improve. The patient repetitively developed and eventually died of bacteremia caused by multidrug-resistant Klebsiella pneumoniae. We highlight the first reported case of TAFRO syndrome after COVID-19 vaccination.

[A case of unresectable intrahepatic cholangiocarcinoma receiving sustainable pembrolizumab therapy].

A 65-year-old man had unresectable intrahepatic cholangiocarcinoma with a malignant biliary stricture. We used an endoscopic plastic stent to drain the bile. Despite receiving standard chemotherapy, the tumor eventually progressed and cancerous peritonitis developed. We had to exchange plastic stents frequently because of stent occlusion. We had a re-biopsy with EUS-FNA and tested for microsatellite instability, which came back as MSI-high. We administered pembrolizumab, which resulted in a significant reduction of tumor size. We were able to administer long-term chemotherapy without serious side effects by repeatedly exchanging plastic stents for stent occlusion. He has maintained partial response for more than 20 months after receiving pembrolizumab.

Does methotrexate have no beneficial effect in reducing flares in the treatment of polymyalgia rheumatica patients?

We read the article by Marsman et al. regarding the efficacy of methotrexate (MTX) in the treatment of polymyalgia rheumatica (PMR) with great interest. This study added new insights regarding the use of MTX in a real-world clinical setting and its effect on the incidence rates of flares. However, we would like to voice our concerns regarding the definition of the participants and interventions that were performed in the study, as well as the comparability of the intervention and control groups. Our concerns include the possibility of the inadvertent enrollment of patients with rheumatoid arthritis in a study on PMR, a lack of a clear definition of glucocorticoid ineffectiveness, a lack of adjustment of glucocorticoid dosages, and a reliance on the judgement of individual medical providers rather than clearly defined investigative guidelines in the study procedures. To summarize, we would like to voice concerns about how and to whom MTX was prescribed, as well as the definition of the control group. These revisions and modifications would clarify the importance of the results regarding the efficacy of MTX administration in the treatment of PMR.

Induction of adaptive immune responses against antigens incorporated within the capsid of simian virus 40.

Simian virus 40 (SV40) is a monkey polyomavirus. The capsid structure is icosahedral and comprises VP1 units that measure 45 nm in diameter. Five SV40 VP1 molecules form one pentamer subunit, and a single icosahedral subunit comprises 72 pentamers; a single SV40 VP1 capsid comprises 360 SV40 VP1 molecules. In a previous study, we showed that an influenza A virus matrix protein 1 (M1) CTL epitope inserted within SV40 virus-like particles (VLPs) induced cytotoxic T lymphocytes (CTLs) without the need for an adjuvant. Here, to address whether SV40 VLPs induce adaptive immune responses against VLP-incorporated antigens, we prepared SV40 VLPs containing M1 or chicken ovalbumin (OVA). This was done by fusing M1 or OVA with the carboxyl terminus of SV40 VP2 and co-expressing them with SV40 VP1 in insect cells using a baculovirus vector. Intraperitoneal (i.p.) or intranasal administration of SV40 VLPs incorporating M1 induced the production of CTLs specific for the M1 epitope without the requirement for adjuvant. The production of antibodies against SV40 VLPs was also induced by i.p. administration of SV40 VLPs in the absence of adjuvant. Finally, the administration of SV40 VLPs incorporating OVA induced anti-OVA antibodies in the absence of adjuvant; in addition, the level of antibody production was comparable with that after i.p. administration of OVA plus alum adjuvant. These results suggest that the SV40 capsid incorporating foreign antigens can be used as a vaccine platform to induce adaptive immune responses without the need for adjuvant.

Dopamine regulates cytokine secretion during innate and adaptive immune responses.

Dopamine (DA) is synthesized by various immune cells. DA receptors (DARs), which comprise five isoforms, are expressed on the surface of these cells. Therefore, it is likely that DA plays a role in regulating innate and adaptive responses. However, the underlying molecular mechanism(s) is largely unknown. Here, we found that, during innate immune responses, DA suppressed secretion of IFN-γ, TNF-α and IL-1ß, but promoted secretion of IL-10 and CXCL1 by lipopolysaccharide (LPS)-stimulated mouse splenocytes, suggesting that DA regulates cytokine secretion. Immune subset studies indicated that DA suppressed secretion of IFN-γ, TNF-α and IL-1ß by NK cells, as well as secretion of TNF-α by neutrophils and monocytes; however, DA up-regulated IL-10 secretion by neutrophils, monocytes, B cells, macrophages (Mφs) and dendritic cells within the splenocyte population. In addition, DA up-regulated secretion of CXCL1 by LPS-stimulated NK cells and Mφs. Meanwhile, treatment with DAR agonists or antagonists suppressed secretion of inflammatory cytokines from LPS-stimulated splenocytes. Pre-treatment of LPS-stimulated splenocytes with the PI3K inhibitor wortmannin reversed DA-mediated suppression of IFN-γ secretion, indicating that DA regulates IFN-γ secretion via the inositol 1,4,5-trisphosphate signaling pathway in these cells. Administration of DA and LPS to mice immunized with chicken ovalbumin (OVA) increased secretion of IL-5 by mouse lung lymphocytes, suggesting that DA promotes OVA-specific Th2-mediated immune responses by these cells. Taken together, these findings indicate that DA regulates cytokine secretion during innate and adaptive immune responses.

T-Cell Responses to Tyrosinase-Derived Self-Peptides in Patients with Leukoderma Induced by Rhododendrol: Implications for Immunotherapy Targeting Melanoma.

BACKGROUND: Rhododendrol, a phenolic compound contained in lightening/whitening cosmetics, can bind and inhibit tyrosinase and was reported to induce leukoderma in Japan. Only 2% of the cosmetics users are affected, and tacrolimus is effective in treatment of the condition. OBJECTIVE: To test the hypothesis that the disease is an autoimmune disorder. METHODS: Short-term T-cell lines were established using peripheral blood mononuclear cells from 8 patients with human melanoma-associated and tyrosinase-derived synthetic peptides. The effects of rhododendrol on melanoma immunization were also examined. RESULTS: Seven out of 8 patients were positive for HLA-DR4. Both class I- and class II-restricted and tyrosinase peptide-specific T-cell responses were observed. Immunization of mice with rhododendrol-treated and irradiated B16 melanoma cells successfully delayed the growth of melanoma cells in vivo. CONCLUSION: Rhododendrol-induced leukoderma is an autoimmune disorder, with rhododendrol as an environmental factor and HLA-DR4 as a genetic factor. Rhododendrol might be effective in treating melanomas.

Dopamine induces IL-6-dependent IL-17 production via D1-like receptor on CD4 naive T cells and D1-like receptor antagonist SCH-23390 inhibits cartilage destruction in a human rheumatoid arthritis/SCID mouse chimera model.

A major neurotransmitter dopamine transmits signals via five different seven-transmembrane G protein-coupled receptors termed D1-D5. Several studies have shown that dopamine not only mediates interactions into the nervous system, but can contribute to the modulation of immunity via receptors expressed on immune cells. We have previously shown an autocrine/paracrine release of dopamine by dendritic cells (DCs) during Ag presentation to naive CD4(+) T cells and found efficacious results of a D1-like receptor antagonist SCH-23390 in the experimental autoimmune encephalomyelitis mouse model of multiple sclerosis and in the NOD mouse model of type I diabetes, with inhibition of Th17 response. This study aimed to assess the role of dopaminergic signaling in Th17-mediated immune responses and in the pathogenesis of rheumatoid arthritis (RA). In human naive CD4(+) T cells, dopamine increased IL-6-dependent IL-17 production via D1-like receptors, in response to anti-CD3 plus anti-CD28 mAb. Furthermore, dopamine was localized with DCs in the synovial tissue of RA patients and significantly increased in RA synovial fluid. In the RA synovial/SCID mouse chimera model, although a selective D2-like receptor antagonist haloperidol significantly induced accumulation of IL-6(+) and IL-17(+) T cells with exacerbated cartilage destruction, SCH-23390 strongly suppressed these responses. Taken together, these findings indicate that dopamine released by DCs induces IL-6-Th17 axis and causes aggravation of synovial inflammation of RA, which is the first time, to our knowledge, that actual evidence has shown the pathological relevance of dopaminergic signaling with RA.

Dopamine D1-like receptor antagonist attenuates Th17-mediated immune response and ovalbumin antigen-induced neutrophilic airway inflammation.

Allergic airway inflammation is generally considered a Th2-type immune response. Recent studies, however, demonstrated that Th17-type immune responses also play important roles in this process, especially in the pathogenesis of neutrophilic airway inflammation, a hallmark of severe asthma. We previously reported that dendritic cells release dopamine to naive CD4(+) T cells in Ag-specific cell-cell interaction, in turn inducing Th17 differentiation through dopamine D1-like receptor (D1-like-R). D1-like-R antagonist attenuates Th17-mediated diseases such as experimental autoimmune encephalomyelitis and autoimmune diabetes. However, the effect of antagonizing D1-like-R on Th17-mediated airway inflammation has yet to be studied. In this study, we examined whether D1-like-R antagonist suppresses OVA-induced neutrophilic airway inflammation in OVA TCR-transgenic DO11.10 mice and then elucidated the mechanism of action. DO11.10 mice were nebulized with OVA or PBS, and some mice received D1-like-R antagonist orally before OVA nebulization. D1-like-R antagonist significantly suppressed OVA-induced neutrophilic airway inflammation in DO11.10 mice. It also inhibited the production of IL-17 and infiltration of Th17 cells in the lung. Further, D1-like-R antagonist suppressed the production of IL-23 by lung CD11c(+) APCs. In contrast, D1-like-R antagonist did not increase Foxp3(+) regulatory T cells in the lung. D1-like-R antagonist neither suppressed nonspecific LPS-induced neutrophilic airway inflammation nor OVA-induced eosinophilic airway inflammation. These results indicate that D1-like-R antagonist could suppress Th17-mediated neutrophilic airway inflammation, raising the possibility that antagonizing D1-like-R serves as a promising new strategy for treating neutrophil-dominant severe asthma.

Ropinirole inhibits inflammatory cytokine production in gingival epithelial cells and suppresses alveolar bone loss in an experimental rat model of periodontitis.

The present study explored whether the dopamine 2-like receptor agonist, ropinirole, a drug used for treating Parkinson's disease, suppresses neutrophilic inflammation and alveolar bone loss in an experimental rat model of periodontitis. Periodontitis is a neutrophilic inflammatory disease caused by periodontal pathogens. An excessive T helper (Th)17 immune response is involved in the progression of periodontitis, and interleukin (IL)-17 promotes the exacerbation of inflammation and alveolar bone destruction. Recent evidence has suggested that dopamine signaling plays a key role in Th17 cell differentiation, and that dopamine 2-like receptor agonists suppress cytokine production from Th17 cells. We previously demonstrated that tannic acid, which is a dopamine 2-like receptor agonist, inhibits alveolar bone resorption in an experimental model of periodontitis. The present study used a carrageenan-induced rat model of periodontitis with or without ropinirole. Micro-computed tomography analysis was performed. Cells of the murine gingival epithelial cell line GE1 were stimulated with carrageenan and IL-17A in the presence or absence of ropinirole. The anti-inflammatory effect of ropinirole was analyzed using reverse transcription- quantitative PCR and enzyme-linked immunosorbent assay. Subsequently, in the carrageenan-induced rat model of periodontitis, alveolar bone resorption was observed in the maxillary second molar by micro-computed tomography analysis. Intriguingly, ropinirole suppressed the alveolar bone destruction. The expression levels of C-X-C motif chemokine ligand 1 (CXCL1) and IL-17 receptor A (IL-17RA) in GE1 cells were increased by carrageenan, and CXCL1 expression in GE1 cells was upregulated under IL-17A stimulation. Moreover, ropinirole inhibited CXCL1 and IL-17RA expression in GE1 cells in the presence of IL-17A and carrageenan. Finally, haloperidol promoted CXCL1 expression in GE1 cells in the presence of carrageenan. Overall, these findings suggested that ropinirole suppressed neutrophilic inflammation and alveolar bone destruction in periodontitis by inhibiting CXCL1 expression in gingival epithelial cells through the dopamine 2-like receptor. Thus, ropinirole shows promise as a drug for the treatment of periodontitis.

Coenzyme A contained in mothers' milk is associated with the potential to induce atopic dermatitis.

T(h)2 adjuvant activity can be qualitatively and quantitatively evaluated using a mixed lymphocyte reaction and by changes in the intracellular cyclic adenosine 3',5'-monophosphate concentration, using human dendritic cells in vitro. The current study shows that mothers, whose children (n = 55) developed atopic dermatitis (AD) within 6 months after birth, often demonstrate a higher T(h)2 adjuvant activity in their milk, in comparison to those whose children did not develop such symptoms. Such an activity was recovered in a liquid phase of mothers' milk and was eluted as a single fraction by reversed-phase HPLC. Further analysis of this fraction by mass spectrometry showed that signals originating from a factor with a molecular weight of 767.53 are observed, exclusively in milk with a high T(h)2 adjuvant activity. The mass is exactly that of Coenzyme A (CoA), and indeed, a low concentration of CoA exhibited T(h)2 adjuvant activity both in vitro and in vivo. Moreover, mesenteric lymph node non-T cells obtained from mice that were orally treated with CoA led allogeneic naive CD4(+) T cells to differentiate into T(h)2. Furthermore, the oral administration of CoA induced rough skin, hyperplasia of the epidermis, hypergranulosis in the spinous layer and the thickening of the stratum in mice. These data collectively indicate that some of the patients with AD were exposed to mothers' milk carrying high T(h)2 adjuvant activity right after birth, which may be attributable to presence of CoA contained in the milk.

Neutrophilic inflammation in severe asthma.

Neutrophils may play an important role in the pathogenesis of severe asthma. Their infiltration into the airway is increased. Interleukin (IL)-8 is involved in this process, and is actually upregulated in the airways of patients. We have observed that in the absence of eosinophil chemoattractants, neutrophils stimulated by IL-8 augment eosinophil trans-basement membrane migration by releasing superoxide anion, matrix metalloproteinase, leukotriene B(4) and platelet-activating factor. These findings suggest that IL-8-stimulated neutrophils could lead eosinophils to accumulate in the airways of asthmatic patients, which might be a mechanism for corticosteroid resistance in severe asthma. However, the mechanisms of IL-8 upregulation in the airway are not completely understood. Several studies suggest that IL-17 (or T helper 17 cells; Th17) is involved in the IL-8 upregulation observed in severe asthma. We clarified that dopamine induces Th17 differentiation through dopamine D1-like receptor (D1-like-R), and that the D1-like-R antagonist attenuates Th17-mediated diseases like experimental autoimmune encephalomyelitis. Furthermore, we demonstrated that a D1-like-R antagonist significantly suppressed ovalbumin (OVA)-induced neutrophilic airway inflammation in OVA T cell receptor-transgenic DO11.10 mice through inhibiting Th17-mediated immune responses. Therefore, dopamine D1-like-R antagonists could become useful for treating Th17-mediated neutrophil-dominant severe asthma. As inhaled corticosteroids are known to be less effective for controlling neutrophilic inflammation, a more effective therapeutic strategy for neutrophil-dominant asthma should still be elucidated.

Istradefylline, an adenosine A2a receptor antagonist, inhibits the CD4+ T-cell hypersecretion of IL-17A and IL-8 in humans.

Extracellular adenosine produced from ATP plays a role in energy processes, neurotransmission, and inflammatory responses. Istradefylline is a selective adenosine A2a receptor (A2aR) antagonist used for the treatment of Parkinson's disease. We previously showed using mouse models that adenosine primes hypersecretion of interleukin (IL)-17A via A2aR, which plays a role in neutrophilic inflammation models in mice. This finding suggests that adenosine is an endogenous modulator of neutrophilic inflammation. We, therefore, investigated the in vitro effect of istradefylline in humans. In the present study, using human peripheral blood mononuclear cells (PBMCs), we tested the effect of adenosine, adenosine receptor agonists and istradefylline on cytokine responses using mixed lymphocyte reaction (MLR), PBMCs, CD4+ T cells, and Candida albicans antigen (Ag)-stimulated PBMCs. We showed that adenosine and an A2aR agonist (PSB0777) promoted IL-17A and IL-8 production from human PBMCs, and istradefylline suppressed this response. In addition, istradefylline inhibited not only the IL-17A and IL-8 production induced by adenosine but also that from C. albicans Ag-stimulated PBMCs. These results indicate that adenosine-mediated IL-17A and IL-8 production plays a role in neutrophilic inflammation, against which istradefylline should be effective.

Extracellular adenosine induces hypersecretion of IL-17A by T-helper 17 cells through the adenosine A2a receptor.

Extracellular adenosine, produced from ATP secreted by neuronal or immune cells, may play a role in endogenous regulation of inflammatory responses. Studies show that adenosine induces hypersecretion of IL-17A by CD4+ T cells upon treatment with an A2aR agonist (PSB0777), and that adenosine-mediated IL-17A hypersecretion is suppressed by the A2aR antagonist (Istradefylline) in humans. However, it is unclear whether A2aR downstream signaling is involved in IL-17A hypersecretion. Here, we show that inhibitors of adenyl cyclase (AC), protein kinase A (PKA), and cAMP response element binding protein (CREB) (which are signaling molecules downstream of the Gs protein coupled to the A2aR), suppress IL-17A production, suggesting that activation of A2aR signaling induces IL-17A production by CD4+ T cells. Furthermore, immune subset studies revealed that adenosine induces hypersecretion of IL-17A by T-helper (Th)17 cells. These results indicate that adenosine is an endogenous modulator of neutrophilic inflammation. Administration of an A2aR antagonist to mice with experimental autoimmune encephalomyelitis led to marked amelioration of symptoms. Thus, inhibitors of the novel A2aR-AC-cAMP-PKA-CREB signaling pathway for IL-17A hypersecretion by TCR-activated Th17 cells suppresses adenosine-mediated IL-17A production, suggesting that it may be an effective treatment for Th17-related autoimmune diseases.

Signaling via dopamine and adenosine receptors modulate viral peptide-specific and T-cell IL-8 response in COVID-19.

B-cell but not T-cell responses have been extensively studied using peripheral blood mononuclear cells (PBMCs) obtained from patients with coronavirus disease 2019 (COVID-19). Our recent study showed that not only T-helper (Th) 17 but also Th1 cells directly produce interleukin (IL)-8, a major source of neutrophilic inflammation, which is also known to induce disseminated intravascular coagulation (DIC) in COVID-19 patients. Neutrophilic inflammation caused by IL-17A or IL-8 can be fatal; thus, therapeutic intervention is highly expected. The present study aimed to investigate the T-cell responses in the Japanese patients. We synthesized spike protein-derived 15-mer peptides that are expected to bind to HLA class II allelic products frequently observed in the Japanese population, and checked the T-cell responses in Japanese patients with COVID-19. We have found that (i) patients show marked IL-8 but not IL-17A responses; (ii) these responses are restricted by HLA-DR; and (iii) IL-8 responses are abrogated by a dopamine D2 like receptor (D2R) agonist, ropinirole, and an adenosine A2a receptor (A2aR) antagonist, istradefylline. Compounds used for the treatment of Parkinson's disease may ease DIC in COVID-19. (183 words).

Elevated White Blood Cell Count and Lactate Dehydrogenase Levels Are Important Markers for Diagnosing Relapse of Adult-onset Still's Disease under Tocilizumab Use.

We encountered a case of refractory adult-onset Still's disease (AOSD) with two relapses. Prednisolone and methotrexate were begun as induction therapy, resulting in the patient's first relapse during tapering of prednisolone. After the introduction of tocilizumab, she achieved remission. However, she experienced a second relapse following prednisolone tapering. While lactate dehydrogenase (LDH) levels and white blood cell (WBC) counts increased in both relapses, interleukin-6 (IL-6) suppression resulted in stable C-reactive protein and ferritin levels in the second relapse. A comparison of the two relapses indicated that increases in both WBC counts and LDH levels can aid in the diagnosis of AOSD relapse.

Qualitative evaluation of adjuvant activities and its application to Th2/17 diseases.

Dendritic cells (DCs) are antigen-presenting cells specialized to activate naive T lymphocytes and initiate primary immune responses. The different classes of specific immune responses are driven by the biased development of antigen-specific helper T cell subsets - that is, Th1, Th2, and Th17 cells - that activate different components of cellular and humoral immunity. DCs reside in an immature state in many nonlymphoid tissues such as the skin or airway mucosa which are highly exposed to allergens, pathogens, and chemicals. T cell receptor stimulation with costimulation allows naive Th cells to develop into effector cells, normally accompanied by high-level expression of selective sets of cytokines. The balance of these cytokines and the resulting class of immune responses depend on the conditions under which DCs are primed. Immunomodulators such as lipopolysaccharides/forskolin/curdlan change the nature of DCs to induce Th1/Th2/Th17 cells thereby designated Th1/Th2/Th17 adjuvants. We have recently found that such activities can be scrutinized by using mixed lymphocyte reaction, cAMP, and differential expression of Notch ligand isoforms. Application of these methods for the analyses of atopic dermatitis and experimental autoimmune encephalomyelitis will be discussed.

Therapeutic effect of D1-like dopamine receptor antagonist on collagen-induced arthritis of mice.

Dopamine activates D1-like and D2-like receptors (D1R and D2R). While D1R antagonists have ameliorated the severity of disease in some experimental autoimmune models of mice by promoting interferon (IFN)-γ and inhibiting interleukin (IL)-17 production by T cells, dopamine effects in the immune system are reportedly diverse. To investigate the impact of D1R blockade on an animal model of rheumatoid arthritis (RA), DBA/1 mice with collagen-induced arthritis (CIA) were treated with a selective D1R antagonist, SCH23390, after the primary immunization. This treatment suppressed the severity of the CIA. Nevertheless, serum levels of antibodies to type II collagen were not affected by the treatment. Th1/Th17 differentiation of splenic T cells in the treated animals was not biased. In vitro, when bone marrow-derived macrophages were stimulated in the presence of the D1R antagonist SCH23390, alteration of inflammatory cytokine expression was not observed, but their in vitro differentiation to osteoclasts was inhibited. Co-administration of a selective D1R agonist, A68930, abrogated the in vivo anti-arthritic effect and the in vitro suppression of osteoclastogenesis by the D1R antagonist. Our results argue that D1R blockade is potentially a new approach to the treatment of RA. Its effect could be partly attributable to the inhibition of osteoclastogenesis.

Fibroblasts stimulated via HLA-II molecules produce prostaglandin E2 and regulate cytokine production from helper T cells.

Fibroblasts act as important immune regulatory cells via their ability to cross-talk with T cells accumulating in lesions. Our previous study showed that fibroblasts produce several cytokines and chemokines by crosslinking HLA class II (HLA-II) molecules with monoclonal antibodies or by making T-cell receptor-peptide-HLA complexes. It is thus conceivable that the interaction of T cells and fibroblasts via HLA-II affects fibroblast responses to stimuli. This study used human gingival fibroblasts (HGF) to investigate possible effects of these fibroblast-derived soluble factors on the differentiation of naïve T cells and on the subsequent fibroblast responses. After mixed lymphocyte reaction culture between naïve T cells and allogeneic dendritic cells in the presence of culture supernatant from HGF stimulated via HLA-DQ molecules (DQ-sup), but not via DR, T cells exhibited a Th2-shifted phenotype, thereby producing quantitatively more IL-13 and IL-5 compared with interferon-γ. Astonishingly, analyses to identify possible factors affecting the Th2 polarization secreted from HLA-II-stimulated HGF, prostaglandin E2, was detected only in DQ-sup. The Th2 polarization of naïve T cells was blocked in the presence of supernatants from indomethacin-treated HGF with HLA-DQ stimulation. In addition, we found that the culture supernatants of Th cells activated following mixed lymphocyte reaction culture in the presence of DQ-sup had the potential to induce gene expression of type I and III collagens in HGF. These results suggested that fibroblasts stimulated via HLA-DQ molecules promote Th2 polarization in Th-cell responses and showed the counter activation of collagen synthesis, implicating orchestrated responses among these cells in the fibrosis of chronic inflammatory lesions.