Akiko Oyamada

Tyrosine kinase 2 plays critical roles in the pathogenic CD4 T cell responses for the development of experimental autoimmune encephalomyelitis.

Tyrosine kinase 2 (Tyk2), a member of the JAK family, is involved in IL-12- and IL-23-mediated signaling. In the present study, we examined the roles of Tyk2 in the development of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) by using Tyk2 knockout (KO) mice. In vitro differentiation of Th1 but not Th17 cells was severely impaired in Tyk2 KO CD4 T cells, although Tyk2 KO Th17 cells did not respond to IL-23. Tyk2 KO mice showed complete resistance against EAE with no infiltration of CD4 T cells in the spinal cord. Surprisingly, the number of MOG-specific Th17 cells in the periphery was comparable between KO and wild-type (WT) mice, whereas Th1 cells were greatly reduced in Tyk2 KO mice. Adoptive transfer of MOG-primed WT T cells induced EAE in Tyk2 KO recipients, indicating that Tyk2 in the environment was dispensable for the infiltration of effector T cells into the spinal cord. A reduced but significant number of Tyk2 KO T cells were detected in the spinal cord of mice with EAE, which had been reconstituted with bone marrow cells of WT and KO mice. Furthermore, MOG-immunized Tyk2 KO mice developed EAE after adoptive transfer of MOG-primed WT Th1 cells, which might trigger local inflammation that recruits Th17 cells. Taken together, these results indicate that Tyk2 is critically involved in the pathogenic CD4 T cell responses and thus could be a target molecule for the treatment of autoimmune diseases.

Preferential accumulation of activated Th1 cells not only in rheumatoid arthritis but also in osteoarthritis joints

Objective. It was previously found that Th1 but not Th17 cells were predominant in the joints of rheumatoid arthritis (RA). To verify whether this is a unique feature of CD4 T cells in RA joints, we performed comparative flow cytometric analysis of CD4 T cells in RA and osteoarthritis (OA) joints. Methods. Mononuclear cells were isolated from peripheral blood (PB), synovial membrane (SM), and synovial fluid (SF) from a total of 18 RA and 12 OA patients. The expression of surface molecules and cytokine production of CD4 T cells was examined by a flow cytometer. Results. Most CD4 T cells in RA joints expressed memory/activation markers, such as CD45RO, HLA-DR, and CD69. CCR5 was highly expressed on CD4 T cells in SF but not in PB or SM. With regard to Th17-related molecules, CD4 T cells expressing CCR6 were not enriched in either SF or SM. In contrast, CD161-positive cells were abundant in the joint, many of which, however, produced interferon-γ but not interleukin 17A. Virtually all T cells in OA joints, although much less numerous than in RA joints, expressed activation markers. Th1 cells were predominant in both OA and RA joints, while there were a few Th17 cells. The frequency of Th17 cells in the joint tended to be lower in OA than RA. Conclusion. There was a quantitative but not qualitative difference in CD4 T cells, including the expression of activation markers and cytokine profiles, between RA and OA joints.

Identification of independent susceptible and protective HLA alleles in Japanese autoimmune thyroid disease and their epistasis.

BACKGROUND Autoimmune thyroid disease (AITD) includes Graves disease (GD) and Hashimoto thyroiditis (HT), which partially share immunological features. Determining the genetic basis that distinguishes GD and HT is a key to understanding the differences between these 2 related diseases. AIM The aims of this study were to identify HLA antigens that can explain the immunopathological difference between GD and HT and to elucidate epistatic interactions between protective and susceptible HLA alleles, which can delineate the distinct function of HLA in AITD etiology. DESIGN We genotyped 991 patients with AITD (547 patients with GD and 444 patients with HT) and 481 control subjects at the HLA-A, HLA-C, HLA-B, DRB1, DQB1, and DPB1 loci. A direct comparison of HLA antigen frequencies between GD and HT was performed. We further analyzed an epistatic interaction between the susceptible and protective HLA alleles in the development of GD and HT. RESULTS We identified 4 and 2 susceptible HLA molecules primarily associated with GD and HT, respectively, HLA-B*35:01, HLA-B*46:01, HLA-DRB1*14:03, and HLA-DPB1*05:01 for GD and HLA-A*02:07 and HLA-DRB4 for HT. In a direct comparison between GD and HT, we identified GD-specific susceptible class II molecules, HLA-DP5 (HLA-DPB1*05:01; Pc = 1.0 × 10(-9)) and HLA-DR14 (HLA-DRB*14:03; Pc = .0018). In contrast, HLA components on 3 common haplotypes in Japanese showed significant protective effects against the development of GD and HT (HLA-A*24:02-C*12:02-B*52:01-DRB1*15:02-DQB1*06:01-DPB1*09:01 and HLA-A*24:02-C*07:02-B*07:02-DRB1*01:01-DQB1*05:01-DPB1*04:02 haplotypes for GD and HLA-A*33:03-C*14:03-B*44:03-DRB1*13:02-DQB1*06:04-DPB1*04:01 haplotype for GD and HT). Interestingly, the representative protective HLA, HLA-DR13 (HLA-DRB1*13:02), was epistatic to susceptible HLA-DP5 in controlling the development of GD. CONCLUSION We show that HLA exerts a dual function, susceptibility and resistance, in controlling the development of GD and HT. We also show that the protective HLA allele is partially epistatic to the susceptible HLA allele in GD.

Protective Role of Fas-FasL Signaling in Lethal Infection with Herpes Simplex Virus Type 2 in Mice

ABSTRACT Herpes simplex virus type 2 (HSV-2) induces acute local infection followed by latent infection in the nervous system and often leads to the development of lethal encephalitis in immunocompromised hosts. The mechanisms of immune protection against lethal HSV-2 infection, however, have not been clarified. In this study, we examined the roles of Fas-Fas ligand (FasL) signaling in lethal infection with HSV-2 by using mice with mutated Fas (lpr) or FasL (gld) in C57BL/6 background. Both lpr and gld mice exhibited higher mortality than wild-type (WT) C57BL/6 mice after infection with virulent HSV-2 strain 186 and showed significantly increased viral titers in the spinal cord compared with WT mice 9 days after infection, just before the mice started to die. There were no differences in the numbers of CD4+ and CD8+ T cells infiltrated in the spinal cord or in the levels of HSV-2-specific gamma interferon produced by those cells in a comparison of lpr and WT mice 9 days after infection. Adoptive transfer studies demonstrated that CD4+ T cells from WT mice protected gld mice from lethal infection by HSV-2. Furthermore, CD4+ T cells infiltrated in the spinal cord of HSV-2-infected WT mice expressed functional FasL that induced apoptosis of Fas-expressing target cells in vitro. These results suggest that FasL-mediated cytotoxic activity of CD4+ T cells plays an important role in host defense against lethal infection with HSV-2.

Interleukin-21 signaling in B cells, but not in T cells, is indispensable for the development of collagen-induced arthritis in mice

BackgroundInterleukin-21 (IL-21) is a T-cell-derived cytokine whose receptor is expressed on a variety of cells and therefore might have pleiotropic roles in the pathogenesis of rheumatoid arthritis (RA). In this study, we investigated the involvement of IL-21 signaling in the development of collagen-induced arthritis (CIA), an animal model of RA, using IL-21 receptor knockout (Il21r KO) mice.MethodsIl21r KO mice or wild-type (WT) C57BL/6 mice were immunized with chicken type II collagen (CII) emulsified in complete Freund adjuvant on day 0 and were given a boost injection on day 21. The production of anti-CII antibody, development of T-cell and B-cell subsets, and T-cell responses to CII were analyzed. CIA was induced in Rag2 KO mice to which combinations of WT or Il21r KO CD4 T cells and WT or Il21r KO B cells had been transferred, in order to examine the role of IL-21 signaling in each cell subset.ResultsIl21r KO mice were resistant to the development of CIA. CII-specific IgG but not IgM production was impaired in Il21r KO mice. This is consistent with a reduction of germinal center B cells in the draining lymph nodes. In contrast, CII-specific Th1 and Th17 responses were unaffected in Il21r KO mice. There was also no difference in the number of CII-specific follicular helper T cells between WT and Il21r KO mice. By analyzing the development of CIA in T-cell and B-cell mixed transfer experiments, we confirmed that IL-21 receptor expression on B cells, but not on T cells, was essential for the development of CIA.ConclusionIL-21 signaling in B cells, but not in T cells, plays essential roles in the production of pathogenic autoantibodies that induce CIA development.

CD4 T cell-intrinsic IL-2 signaling differentially affects Th1 and Th17 development

IL‐2 signaling is involved in clonal expansion of antigen‐specific CD4 T cells. IL‐2 is also reported to promote Th1 but inhibit Th17 differentiation, although in vivo relevance remains unclear. In addition, IL‐2‐dependent Foxp3+ CD4 Tregs suppress T cell proliferation, complicating the in vivo role of IL‐2 in the development of Th cell responses. To elucidate the roles of cell‐intrinsic IL‐2 signaling in CD4 T cells, we cotransferred TCR‐Tg CD4 T cells from IL‐2Rα (CD25)‐deficient and WT mice and analyzed development of antigen‐specific Th1 and Th17 responses. It was revealed that Th17 development of antigen‐specific CD4 T cells was largely unaffected, whereas Th1 development was impaired by the lack of IL‐2 signaling. Similar data were obtained from mixed BM chimera experiments using BM cells from CD25‐deficient and WT mice. In addition, although in vitro blockade of IL‐2 during Th17 development greatly increased the percentages of Th17 cells, it did not affect their numbers, indicating that in vitro Th17 development is also IL‐2‐independent. Th1 development was dependent on IL‐2 in vitro as well. Thus, our data suggest that cell‐intrinsic IL‐2 signaling is critical for Th1 development but plays a limited role in Th17 development in vitro as well as in vivo.

Tyk2-Dependent Bystander Activation of Conventional and Nonconventional Th1 Cell Subsets Contributes to Innate Host Defense against Listeria monocytogenes Infection

IL-12, which is produced in response to intracellular bacteria, such as Listeria monocytogenes, promotes the development of pathogen-specific Th1 cells that play an important role in host defense. However, it has also been known that CD44high memory-phenotype CD4 T cells with Th1 functions naturally occur in naive mice, and that lymphopenia-induced proliferation of naive CD4 T cells generates memory-phenotype CD4 T cells with Th1 functions, although their differentiation mechanism and contribution to host defense are unclear. In this study, we analyzed the development and the functions of the different subsets of Th1 cells by using mice lacking tyrosine kinase 2 (Tyk2), a member of the Janus kinase family critically involved in IL-12 signaling. In contrast with the case of conventional Ag-specific Th1 cells, the development of naturally occurring Th1 cells was not impaired in Tyk2-deficient mice. In addition, Th1 cells were normally generated from Tyk2-deficient naive CD4 T cells via lymphopenia-induced proliferation. Nevertheless, all these Th1 subsets, including conventional Ag-induced Th1 cells, produced IFN-γ in response to IL-12 in a Tyk2-dependent manner. Importantly, such Tyk2-dependent bystander IFN-γ production of any Th1 subsets conferred early protection against L. monocytogenes infection. Thus, Tyk2-mediated IL-12 signaling is differentially required for the development of different Th1 cell subsets but similarly induces their bystander IFN-γ production, which contributes to innate host defense against infection with intracellular bacteria.

Outcome of joint-preserving arthroplasty for rheumatoid forefoot deformities

Background: Along with the recent advances in the pharmacological management of rheumatoid arthritis, there is a trend toward the use of joint-preserving surgery in the treatment of rheumatoid forefoot deformities. However, the clinical outcomes of joint-preserving surgery for rheumatoid forefoot deformities have not been assessed in comparison to resection arthroplasty. Methods: We retrospectively evaluated 23 feet in 17 patients with rheumatoid forefoot deformities who underwent surgery between January 2010 and December 2013. The patients included 1 male (1 foot) and 16 females (22 feet), with a mean age of 62 years. The mean length of follow-up was 28 months. The patients were treated by 3 surgeons. One surgeon performed joint-preserving procedures (JP group) to the feet in which (1) no pain with motion existed, and (2) the range of motion in the first metatarsophalangeal (MTP) joint was greater than 30 degrees (n = 10); otherwise, resection arthroplasty with arthrodesis of the first MTP joint was performed (n = 3). The other surgeons performed resection arthroplasty in all cases (n = 10) (RA group, n = 13 in total). The clinical outcomes of the patients were evaluated using the Japanese Society for Surgery of the Foot (JSSF) hallux and lesser toe scales. Results: There were no significant differences in the preoperative total JSSF scores for either the hallux (54.5 and 61.4 points) or the lesser toe (45.2 and 57.4 points) between the RA and JP groups, respectively. Postoperatively, the total JSSF scores for both the hallux (79.4 and 88.2 points) and lesser toes (73.6 and 87.7 points) showed significant improvement in both the RA and JP groups, respectively; however, the JP group showed a greater postoperative improvement. The scores relating to the function category on the hallux scale and the alignment category on the lesser toe scale were significantly higher in the JP group. Conclusion: With regard to the function of the hallux and the alignment of the lesser toes, the joint-preserving procedures for rheumatoid forefoot deformities resulted in better clinical outcomes than resection arthroplasty. Level of Evidence: Level III, comparative case series.

Delayed diagnosis of ankylosing spondylitis in a Japanese population

Abstract Objectives: This study was conducted to evaluate the period from symptom onset to diagnosis of ankylosing spondylitis (AS) in Japanese patients and to examine possible reasons for delayed diagnosis. Methods: Seventy-two consecutive patients with AS were studied. Diagnostic delay was defined as the gap between the first spondyloarthropathic symptom and diagnosis of AS according to the modified New York criteria. Results: The mean patient ages at disease onset and diagnosis were 25.6 ± 11.3 and 33.3 ± 13.2 years old, respectively, resulting in diagnostic delay of 6.7 years. The number of medical institutions to which patients were referred before diagnosis was 2.4, and orthopedic surgeons were most commonly visited (62%). Non-specific low back pain or lumbar spondylitis (33%) and degenerative arthritis (28%) were the primary diagnoses preceding that of AS. Absence of articular symptoms significantly correlated with diagnostic delay. The patients with disease onset on year 2000 or later had significantly shorter periods until diagnosis than those before 2000 (3.6 vs. 7.5 years). Conclusions: The present study showed a marked diagnostic delay among Japanese patients with AS. Although it has been improved, continuing medical education focusing on inflammatory back pain in adolescent is required for early diagnosis of AS.

Methotrexate-related lymphoproliferative disorder presenting with severe swelling of the elbow joint

Case: A patient with rheumatoid arthritis (RA) who was being treated with methotrexate (MTX) therapy presented with severe swelling of the left elbow. Magnetic resonance imaging showed a tumor-like lesion around the elbow joint. Fluorodeoxyglucose positron emission tomography indicated multiple lesions in the lung and the lymph nodes. An open biopsy of a cervical lymph node was performed, and MTX-related lymphoproliferative disorder (MTX-LPD) was diagnosed. After cessation of the MTX therapy, the elbow swelling regressed, and the patient was in remission of MTX-LPD. Conclusion: MTX-LPD should be considered in the differential diagnosis when a patient with RA develops severe joint swelling while on MTX therapy.