Okayama University Medical SchoolActa Medica Okayama0386-300X7052016An Open-labeled, Multicenter Phase II Study of Tamibarotene in Patients with Steroid-refractory Chronic Graft-versus-Host Disease409412ENYoshinobuMaedaDepartment of Hematology and Oncology, Okayama University HospitalHisakazuNishimoriDepartment of Hematology and Oncology, Okayama University HospitalYoshihiroInamotoDepartment of Hematopoietic Stem Cell Transplantation, National Cancer Center HospitalHirohisaNakamaeDepartment of Hematology, Osaka City University HospitalMasashiSawaDepartment of Hematology and Oncology, Anjo Kosei HospitalYasuoMoriDepartment of Medicine and Biosystemic Science, Kyushu University Graduate School of Medical SciencesKazuteruOhashiHematology Division, Tokyo Metropolitan Cancer and Infectious Diseases CenterShin-ichiroFujiwaraDivision of Hematology, Department of Medicine, Jichi Medical UniversityMitsuneTanimotoDepartment of Hematology and Oncology, Okayama University HospitalClinical Study Protocols10.18926/AMO/54603Chronic graft-versus-host disease (GVHD) is a major cause of late death and morbidity following allogeneic hematopoietic cell transplantation (HSCT). Retinoic acid (tamibarotene) exerts multiple effects on cell differentiation and is clinically used for the treatment of acute promyelocytic leukemia. Tamibarotene down-regulates both Th1 and Th17 differentiation in donor T cells after allogeneic HSCT, resulting in attenuation of experimental chronic GVHD. Based on preclinical data, we have launched a phase II study of tamibarotene in patients with steroid-refractory chronic GVHD. This study will clarify whether tamibarotene can exert beneficial effects in patients with steroid-refractory chronic GVHD.No potential conflict of interest relevant to this article was reported.Springer-VerlagActa Medica Okayama0941-43552122013Antibiotic sensitivity of bacteria on the oral mucosa after hematopoietic cell transplantation367368ENYoshihikoSogaYoshinobuMaedaMitsuneTanimotoTakayukiEbinumaHiroshiMaedaShogoTakashibaNo potential conflict of interest relevant to this article was reported.Springer Berlin HeidelbergActa Medica Okayama0941-43552262014Distribution of oral mucosal bacteria with mecA in patients undergoing hematopoietic cell transplantation16791683ENTakayukiEbinumaYoshihikoSogaTakamaroSatoKazuyukiMatsunagaChiekoKudoHiroshiMaedaYoshinobuMaedaMitsuneTanimotoShogoTakashiba[Purpose]
We recently reported frequent detection of antibiotic-resistant bacteria on the oral mucosa during the period of hematopoietic cell transplantation (HCT) and suggested an association between oral mucositis and antibiotic-resistant bacterial infection. Methicillin-resistant Staphylococcus spp. were frequently detected, and the oral cavity may be a reservoir of the gene mediating methicillin resistance, mecA. Here, we examined the frequency of mecA carriers in patients undergoing HCT.
[Methods]
Fifty-nine patients (male (M) = 37, female (F) = 22, 47.3 ± 11.0 years) receiving HCT were enrolled in this study. Buccal swab samples were obtained four times from day −7 to day +20 (once/week), and mecA was detected by PCR. Fifty-two subjects without systemic disease, who completed dental treatment, especially periodontal treatment (M = 21, F = 31, 55.4 ± 14.2 years), were also enrolled as controls and checked for mecA on the oral mucosa.
[Results]
Seventy-six percent (45/59) of the HCT patients carried mecA at least once in the study period (days −7 to +20), while no control subjects had mecA. The frequency of mecA carriers was 19.2 % from days −7 to −1, while it was significantly increased on days +7 to +13 and +14 to +20, with frequencies of 60.9 and 63.2 %, respectively (P < 0.01, ANOVA).
[Conclusions]
mecA was detected in oral mucosa of patients undergoing HCT. The high detection frequency of staphylococci resistant to penicillin and beta-lactams in our recent report was supported.No potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812722015慢性移植片対宿主病に対するタミバロテン(AM80G)の医師主導臨床第U相試験133137ENHisakazuNishimoriYoshinobuMaedaNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama0046-81774572014Low-grade B-cell lymphoma presenting primarily in the bone marrow13791387ENKayokoIwataniKatsuyoshiTakataYasuharuSatoTomokoMiyata-TakataNorikoIwakiWeiCuiSeikoSawada-KitamuraHiroshiSonobeMaikoTamuraKatsuhikoSaitoKatsuyaMiyataniRieYamasakiIchiroYamadoriNobuharuFujiiYasushiTerasakiYoshinobuMaedaMitsuneTanimotoNaoyaNakamuraTadashiYoshinoCases of low-grade B-cell lymphoma presenting primarily in the bone marrow are rare, and its clinicopathology remains unclear. We retrospectively examined patients with low-grade B-cell lymphoma presenting primarily in the bone marrow. Fourteen patients met the inclusion criteria, including 5 with lymphoplasmacytic lymphoma (LPL), 3 with chronic lymphocytic leukemia/small lymphocytic lymphoma, 2 with follicular lymphoma (FL), and 4 with low-grade B-cell lymphoma not otherwise specified (LGBCL-NOS). The median age was 69.5 years (range, 42-89 years), and a slight male predominance was noted (9 men and 5 women, 1.8: 1). Immunohistochemically, all cases were positive for CD20. One case was positive for CD138. Both cases of FL were positive for CD10 and B-cell lymphoma 2 (BCL-2), and immunoglobulin heavy locus (IgH)/B-cell lymphoma 2 rearrangement was observed by fluorescence in situ hybridization. The myeloid differentiation primary response gene (88) leucine to proline mutation was observed in 3 of 5 LPL, 1 of 2 FL, and 2 of 4 LGBCL-NOS patients. Paraproteinemia was observed in 10 patients; IgM and IgG paraproteinemia were observed in 6 and 3 patients, respectively. In this patient series, 3 patients had died at a median follow-up of 36.5 months; the cause of death of 1 LPL patient was malignant lymphoma itself. Thus, low-grade B-cell lymphoma presenting primarily in the bone marrow has various subtypes, and approximately one-third of the patients had LGBCL-NOS. The immunophenotypic features and myeloid differentiation primary response gene (88) leucine to proline mutation data of LGBCL-NOS suggested that some cases present with characteristics similar to those of LPL or marginal zone lymphoma.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1083-87912022014Mammalian Target of Rapamycin Inhibitors Permit Regulatory T Cell Reconstitution and Inhibit Experimental Chronic Graft-versus-Host Disease183191ENHarukoSugiyamaYoshinobuMaedaHisakazuNishimoriYoshikoYamasujiKen-ichiMatsuokaNobuharuFujiiEiseiKondoKatsujiShinagawaTakehiroTanakaKengoTakeuchiTakanoriTeshimaMitsuneTanimotoChronic graft-versus-host disease (GVHD) remains a major late complication of allogeneic bone marrow transplantation (BMT). In a previous study, impaired thymic negative selection of the recipients permitted the emergence of pathogenic T cells that cause chronic GVHD using MHC class II-deficient (H2-Ab1 KO) B6 into OH model and CD4(+) T cells isolated from chronic GVHD mice caused chronic GVHD when administered into the secondary recipients. In this study, we evaluated the kinetics of regulatory T cell (Treg) reconstitution in wild type B6 into C3H model. After myeloablative conditioning, host Tregs disappeared rapidly, followed by expansion of Tregs derived from the donor splenic T cell inoculum. However, the donor splenic T cell derived Treg pool contracted gradually and was almost completely replaced by newly generated donor bone marrow (BM)-derived Tregs in the late post-transplantation period. Next, we compared the effects of cyclosporine (CSA) and mammalian target of rapamycin (mTOR) inhibitors on Treg reconstitution. Administration of CSA significantly impaired Treg reconstitution in the spleen and thymus. In contrast, BM-derived Treg reconstitution was not impaired in mTOR inhibitor-treated mice. Histopathological examination indicated that mice treated with GSA, but not mTOR inhibitors, showed pathogenic features of chronic GVHD on day 120. Mice treated with CSA until day 60, but not mTOR inhibitors, developed severe chronic GVHD followed by adoptive transfer of the pathogenic CD4(+) T cells isolated from H2-Ab1 KO into C3H model. These findings indicated that long-term use of CSA impairs reconstitution of BM-derived Tregs and increases the liability to chronic GVHD. The choice of immunosuppression, such as calcineurin inhibitor-free GVHD prophylaxis with mTOR inhibitor, may have important implications for the control of chronic GVHD after BMT.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1618-124710022012Histological and immunohistochemical features of gingival enlargement in a patient with AML254257ENNorihiroSonoiYoshihikoSogaHiroshiMaedaKoichiIchimuraTadashiYoshinoKazutoshiAoyamaNobuharuFujiiYoshinobuMaedaMitsuneTanimotoRichardLoganJudithRaber-DurlacherShogoTakashibaHere, we discuss the pathophysiology of leukemia-associated gingival enlargement based on a case of acute myelomonocytic leukemia (AML-M4) with typical gingival enlargement. Uniquely, this patient was well enough to allow full periodontal examination and incisional gingival biopsy to be performed both before and after chemotherapy. The patient was a 39-year-old Japanese woman with AML-M4 showing gingival enlargement. Histological and immunohistochemical features of gingiva and bacterial counts in the periodontal pockets were examined before and after chemotherapy. The results were as follows: (1) infiltration of myelomonocytic blasts in enlarged gingiva; (2) resolution of gingival enlargement with complete remission of AML by anticancer chemotherapy; and (3) the numbers of bacteria in the periodontal pockets were not high and were not altered before or after chemotherapy. In patients with AML-M4, remarkable mucosal enlargement is not generally observed in the body except in the gingiva. We hypothesized that antigens derived from periodontal bacteria, even if they are not present in large numbers, could act as chemoattractants for myelomonocytic leukemic cells.No potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812622014リンパ腫・骨髄腫143150ENKyosukeSaekiYoshinobuMaedaMitsuneTanimotoNo potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812612014白血病および白血病類縁疾患における分子標的治療4954ENYoshinobuMaedaMitsuneTanimotoNo potential conflict of interest relevant to this article was reported.電通サドラー・アンド・ヘネシー株式会社Acta Medica Okayama202010移植後合併症の看護ポイント─GVHDB 口腔GVHD23ENNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama0046-81774492013Distinct morphologic, phenotypic, and clinical-course characteristics of indolent peripheral T-cell lymphoma19271936ENEikoHayashiKatsuyoshiTakataYasuharuSatoYukieTashiroYoshiroTachiyamaSeikoSawada-KitamuraYasushiHiramatsuShunSugiguchiSoichiroNoseMitsuyoshiHirokawaMidoriAndoLamiaAbd MaderYoshinobuMaedaMitsuneTanimotoTadashiYoshinoPeripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) consists of a heterogeneous group of lymphomas. Patients. generally show an aggressive clinical course and very poor outcome. Although the 2008 World Health Organization classification of PTCL-NOS includes 3 variants, low-grade lymphoma is not Included. Of 277 PTCL-NOS cases recorded in our consultation files, we examined the clinicopathologic characteristics of 10 patients with T-cell lymphomas composed of small-sized cells with slight nuclear atypia. Eight patients showed extranodal involvement (5 patients, spleen; 3 patients, thyroid), and 5 patients were at clinical stage I or II. Histologically, all samples presented diffuse infiltrate of small lymphoid cells, with few mitotic figures. Immunohistologically, all samples were positive for CD3, and CD:20 Was detected in 5 samples. All samples showed a low Ki-67 labeling index (mean, 1.05%), and 7 samples were positive for central memory T-cell markers. Clonal T-cell receptor gamma chain and/or alpha-beta chain gene rearrangements were detected in all 10 patients. Five patients received chemotherapy, whereas for 3 patients, treatment consisted only of observation following surgical resection of the spleen or thyroid. Nine patients were alive at a median follow-up time of 19.5 months, whereas 1 patient died of an unrelated disease. The present study strongly indicates that T-cell lymphoma with small-sized lymphoma cells and a low Ki-67 labeling index is a distinct variant. Recognition of this novel lymphoma subtype, which should not be defined merely as PTCL-NOS, should be seriously considered.No potential conflict of interest relevant to this article was reported.Okayama University Medical SchoolActa Medica Okayama0386-300X6752013Preparation of Enteric-coated Capsules of Beclomethasone Dipropionate for Patients with Intestinal Graft-versus-Host Disease and a Case Study319324ENKiminakaMurakawaTomoakiSatoYoshinobuMaedaYoshihisaKitamuraMitsuneTanimotoToshiakiSendoCase Report10.18926/AMO/51868Graft-versus-host disease (GVHD) is a major concern in transplantation patients. Gut GVHD is accompanied by diarrhea, abdominal pain, and/or melena. Although oral treatment with corticosteroids (CSs) is effective in treating gut GVHD, it can cause adverse reactions that affect the entire body. Topical administration of CSs can be effective in treating diseases in which lesions are limited locally, because adverse reactions can then be alleviated. In this study, we examine and discuss an enteric-coated beclomethasone dipropionate (BDP) capsule (BDP-EC) formulated at Okayama University Hospital. The BDP-EC did not dissolve in solution 1 (pH1.2), and began disintegrating in solution 2 (pH6.8) after 5min, with a mean dissolution rate at 15min of 85%. We then used the capsule to treat a patient who developed gut GVHD after allogeneic hematopoietic stem cell transplantation. Clinically, the frequency of diarrhea decreased after BDP-EC administration. In addition, we were able to decrease the prednisolone equivalent dose. Symptoms associated with adverse reactions to BDP were not observed during the hospitalization period. These findings suggest that the administration of BDP-EC in the early stages of gut GVHD may allow a reduction in the initial doses of systemic CSs.No potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812522013十二指腸濾胞性リンパ腫はAIDの発現を欠くがBACH2の発現を有しmemoryB細胞としての性質を有する103107ENKatsuyoshiTakataYasuharuSatoNaoyaNakamuraMamiTokunakaYukariMikiYara YukieKikutiKazuhikoIgarashiEtsuroItoHideoHarigaeSeiichiKatoEikoHayashiTakashiOkaYoshinobuHoshiiAkiraTariHiroyukiOkadaABD Alkader LamiaMohamadoYoshinobuMaedaMitsuneTanimotoTomohiroKinoshitaTadashiYoshinoNo potential conflict of interest relevant to this article was reported.Okayama University Medical SchoolActa Medica Okayama0386-300X6712013Chronic Graft-versus-Host Disease: Disease Biology and Novel Therapeutic Strategies18ENHisakazuNishimoriYoshinobuMaedaMitsuneTanimotoReview10.18926/AMO/49251Graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation. Chronic GVHD often presents with clinical manifestations that resemble those observed in autoimmune diseases. Standard treatment is 1-2mg/kg/day of prednisone or an equivalent dose of methylprednisolone, with continued administration of a calcineurin inhibitor for steroid sparing. However, the prognosis of steroid-refractory chronic GVHD remains poor. Classically, chronic GVHD was said to involve predominantly Th2 responses. We are now faced with a more complex picture, involving possible roles for thymic dysfunction, transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF), B cells and autoantibodies, and Th1/Th2/Th17 cytokines, as well as regulatory T cells (Tregs), in chronic GVHD. More detailed research on the pathophysiology of chronic GVHD may facilitate the establishment of novel strategies for its prevention and treatment.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0941-43551972011Bacterial substitution of coagulase-negative staphylococci for streptococci on the oral mucosa after hematopoietic cell transplantation9951000ENYoshihikoSogaYoshinobuMaedaFumihikoIshimaruMitsuneTanimotoHiroshiMaedaFusanoriNishimuraShogoTakashibaCoagulase-negative staphylococci (CoNS) are frequently isolated from blood cultures of hematopoietic cell transplantation (HCT) patients. Generally, the use of central venous catheters is recognized as a significant risk factor for CoNS infection, while the impact of CoNS infection from oral ulcerative mucositis, which occurs frequently in HCT, may be underestimated. Here, we examined the bacteria on the buccal mucosa after HCT.
Sixty-one patients were examined for bacteria on the buccal mucosa routinely once a week from 1 week before to 3 weeks after allogeneic HCT. Subjects were divided into groups with short and long periods of antibiotic use, and differences in bacterial substitution were evaluated. The relationships between type of HCT (conventional HCT or RIST) and bacterial substitution were also evaluated.
The changes in detection frequencies of CoNS and alpha-streptococci from before to 3 weeks after HCT were significant (P < 0.05, chi (2) test): 14.5-53.3% and 92.7-53.1%, respectively. Significant bacterial substitution of CoNS for streptococci was observed in the long-term antibiotic use group (P < 0.05, chi (2) test), but also occurred in cases with short-term or no antibiotic use. No relationships between type of HCT (conventional HCT or RIST) were observed.
Bacterial substitution of CoNS for streptococci occurred frequently on the buccal mucosa after HCT. In addition to antibiotic use, environmental factors may be involved in bacterial substitution. It is important to consider the presence of oral mucositis in CoNS infection after HCT.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0941-43551812010Oral mucositis in patients receiving reduced-intensity regimens for allogeneic hematopoietic cell transplantation: comparison with conventional regimen115119ENKanayoTakahashiYoshihikoSogaYumenoMurayamaMikaUdagawaHitomiNishimotoYukoSugiuraYoshinobuMaedaMitsuneTanimotoShogoTakashibaSevere oral mucositis induced by allogeneic hematopoietic cell transplantation (HCT) is associated with intolerable pain and risk of systemic bacteremia infection. Differences between conventional HCT and reduced-intensity regimens for allogeneic HCT (RIST) may influence the occurrence and severity of oral mucositis. Here, we evaluated oral mucositis in patients undergoing RIST and compared the results with those in conventional allogeneic HCT patients to facilitate predictive measures for mucositis.
A total of 127 consecutive patients undergoing HCT (conventional, 63; RIST, 64) were included in this study. Severity of oral mucositis during HCT period was evaluated daily. Differences in severity of mucositis among HCT types were analyzed. Use of morphine to control pain due to oral mucositis was evaluated in each HCT method.
The severity of oral mucositis was reduced in patients undergoing RIST. Worsening of oral mucositis was delayed in patients receiving RIST. Use of morphine to control pain due to oral mucositis was significantly decreased in patients undergoing RIST compared with those receiving conventional allogeneic HCT.
The severity of oral mucositis was reduced and the peak day of oral mucositis was delayed in RIST patients compared with those receiving conventional HCT.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0941-43551752009Febrile neutropenia and periodontitis: lessons from a case periodontal treatment in the intervals between chemotherapy cycles for leukemia reduced febrile neutropenia581587ENYoshihikoSogaYoshikoYamasujiChiekoKudoKaoriMatsuura-YoshimotoKokoroYamabeYukoSugiuraYoshinobuMaedaFumihikoIshimaruMitsuneTanimotoFusanoriNishimuraShogoTakashibaOral and systemic infections arising from the oral cavity are significant problems in clinical management of patients undergoing leukemia treatment. However, there is significant disparity in the reported incidences of development of periodontal infections. Evidence is limited to those showing the systemic influence of periodontal infection in neutropenic patients. This study indicated an association between febrile neutropenia (FN) and periodontitis in a case in which periodontal treatment in the intervals between chemotherapy cycles reduced FN in subsequent courses of chemotherapy and hematopoietic transplantation (HCT).
Periodontal treatment was performed in a 61-year-old man with advanced periodontitis, who received HCT following three cycles of chemotherapy. After recovery from neutropenia induced by initial chemotherapy, periodontal treatment was performed in each chemotherapy interval period. Following extraction of teeth with severe advanced periodontitis, all teeth were subjected to periodontal pocket curettage and root planning, which are common periodontal treatments to reduce periodontal pockets harboring anaerobic periodontal bacteria, before HCT.
Periodontal treatment successfully reduced periodontal pockets from 4.1 +/- 1.5 mm to 3.0 +/- 0.6 mm, which was almost within the healthy range (< 3.0 mm), before HCT. The frequency of FN decreased significantly with increasing cycles of chemotherapy, and decreases in FN corresponded to progress of periodontal treatment. Blood cultures obtained a total of 12 times throughout leukemia treatment were all negative.
The observations reported here indicate the importance of periodontal treatment in clinical management of patients undergoing leukemia treatment to prevent FN, although all blood cultures were negative.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0941-43551922011Progress of oral care and reduction of oral mucositis-a pilot study in a hematopoietic stem cell transplantation ward303307ENYoshihikoSogaYukoSugiuraKanayoTakahashiHitomiNishimotoYoshinobuMaedaMitsuneTanimotoShogoTakashibaOral mucositis is a common symptomatic complication associated with hematopoietic stem cell transplantation (HCT). We use simple strategies aimed to reduce oral mucositis by keeping the oral cavity clean and moist. Here, we report on the progress of oral care and the changes in the degree of oral mucositis. The purpose of this pilot study is to evaluate the effects of our strategies on the prevalence and the severity of oral mucositis.
Fifty-three consecutive patients from 2003 to 2006 administered with conventional allogeneic HCT were enrolled in this study. The degree of oral mucositis was evaluated daily in all patients. Our oral care program was divided into two periods: "examination and trial period (2003 and 2004)" and "intensive oral care period (2005 and 2006)." In the latter, an oral care regimen was carried out systematically by a multidisciplinary team.
Using our oral care strategies, the prevalence of ulcerative oral mucositis was decreased significantly. The rate was reduced from 76% (10 of 13) of patients with ulcerative oral mucositis in 2003 to only 20% (3 of 15) in 2006.
Our pilot study suggests that oral mucositis in HCT patients can be alleviated by simple strategies aimed at keeping the oral cavity clean and moist.No potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812432012合成レチノイドAm80はTh1とTh17を抑制することにより慢性移植片対宿主病を改善する197201ENHisakazuNishimoriYoshinobuMaedaMitsuneTanimotoNo potential conflict of interest relevant to this article was reported.岡山医学会Acta Medica Okayama0030-155812412012同種抗原による移植片対白血病効果減弱のメカニズム58ENShojiAsakuraDaigoHashimotoShuichiroTakashimaHarukoSugiyamaYoshinobuMaedaKoichiAkashiMitsuneTanimotoTakanoriTeshimaNo potential conflict of interest relevant to this article was reported.Okayama University Medical SchoolActa Medica Okayama0386-300X6562011Successful Extracorporeal Life Support for Life-threatening Hypercapnia with Bronchiolitis Obliterans after Allogeneic Hematopoietic Stem Cell Transplantation403406ENKoichiWasedaYasushiTanimotoShingoIchibaNobuakiMiyaharaToshiMurakamiNobuakiOchiMichihisaTeradoOsamuNaganoYoshinobuMaedaArihikoKanehiroYoshihitoUjikeMitsuneTanimotoCase Report10.18926/AMO/47266Bronchiolitis obliterans (BO) is a disease with a poor prognosis, and a key factor that limits long-term survival after allogeneic hematopoietic stem cell transplantation (HSCT). We here report a case of a 31-year woman with acute lymphatic leukemia, which was treated by chemotherapy and HSCT, and consequently developed BO 2 years after HSCT. A non-tuberculous mycobacterial infection occurred and showed gradual exacerbation. She started taking anti-mycobacterial drugs, but lost appetite, felt tired and finally lost consciousness one month after beginning medication. Arterial blood gas revealed marked hypercapnia. Using extracorporeal life support (ECLS), the carbon dioxide concentration was reduced and her consciousness recovered. To our knowledge, this is the first case in which ECLS was successfully used for hypercapnia in a patient with BO.No potential conflict of interest relevant to this article was reported.IEEE SMC Hiroshima ChapterActa Medica Okayama1883-3977200912009Evaluation of an economic model composed of producer agents122126ENIn recent years, the existence of a "social divide", comprising factors such as income and professional status, has been noted as one significant type of social issue. It has been stated that, among the disparate groups, a member belonging to one group cannot move to any other groups. Such a rigidity in terms of social status results in non-activation of the economy. In this study, we have suggested a dynamic economic model described by a multi-agent system, and have evaluated its dynamics in order to try to understand the mechanisms by which how the social divide emerges within the model. We used Gini's coefficient to evaluate the social divide and its economic efficiency. As a result, it is suggested that economies under conditions of low competitiveness, being a state composed of relatively more consumer agents than producer agents, display a higher negative relationship between Gini's coefficient and economic efficiency than those under conditions of high competitiveness.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1999Monitoring of human herpesviruses after allogeneic peripheral blood stem cell transplantation and bone marrow transplantationENNo potential conflict of interest relevant to this article was reported.