Cardiac transplantation is governed by complex immunological mechanisms contributing to different types of allograft rejection. Early non-specific graft failure and chronic rejection (cardiac allograft vasculopathy) represent the main limitations for the recipients’ short- and long-term survival respectively. To date, the pathogenesis of both rejection types remains ill-defined. However, it is believed that they are related to an immunologically mediated potent inflammatory process, occurring whether early after transplantation (acute), or lasting for the lifetime of the graft (chronic). The initiating mechanisms of chronic rejection in solid organ transplantation remain ill-defined. Emerging evidence sustains that graft vasculopathy is primarily driven by alloreactive CD4+ T lymphocytes sensitized by the indirect pathway of allorecognition. To date, whereas the nature of APCs involved in this particular pathway has yet to be identified, it appears challenging to speculate that recipient-derived endothelial cells (ECs) repopulating the graft may represent the main cell targets recognized by indirectly primed alloreactive CD4+ T cells to mediate the rejection of cardiac transplants. In the first part of this thesis, we specifically studied the indirect pathway of allorecognition with a transgenic mice (Marilyn mice) model that expresses a T cell receptor (TCR) transgene which recognizes the male antigen H-Y in an I-Ab-restricted fashion. Our results provide evidence that graft endothelium replacement by recipient-type cells expressing MHC Class II molecules is required for the chronic rejection of vascularized cardiac transplants mediated by indirect pathway alloreactive CD4+ T cells. The purpose of the second part of the thesis was to investigate the potential implication of interleukin-22 (IL-22), an early phase secreted proinflammatory cytokine of the IL-10 family, in the acute rejection of cardiac allografts. IL-22 was recently described as an effector key modulator of the inflammatory process produced mainly by differentiated CD4+ T cells of the Th17 lineage. As being closely related to IL-10 and IL-17, both involved in the rejection process of vascularized heart allografts, we attempted to determine the precise role of IL-22 in this process. Experiments were conducted with a recently developed murine model deficient for the IL-22 gene (IL-22KO). The results of the second part of the thesis show that IL-22 is not an effector cytokine in cardiac allograft rejection. In contrast, as being early expressed into the allograft, likely IL-22 plays a protective role in the inflammation leading to acute cardiac rejection, probably depending on a neutrophil-related mechanism. In conjunction with current understanding of inflammatory and antigen-specific events in allografts, overall, our results provide new insights into the mechanisms of chronic and acute cardiac rejection, thus prompting to further interrogations and appealing novel therapeutic strategies. Pharmacologic manipulation of endothelium is challenging. Given their capacity to sense and rapidly respond to the local environment, ECs are the ideal targets for rapid systemic delivery of therapeutic agents. Combination therapy is required to reduce inflammatory reaction and endothelial activation, to modulate endothelial dysfunction and promote endothelial survival. Also, given that IL-22 may alleviate tissue destruction during inflammatory responses, therapies that enhance its production and protective action in the transplanted organs seem attractive to specifically affect tissue responses, without exerting direct effects on the immune response.

Cutaneous lupus erythematosus (CLE) is an autoimmune disease that resolves with or without permanent scars depending on the subtype. Interferons (IFNs), including the skin specific IFNλ mainly activate STAT1, which results in inflammation in CLE and may play a significant role in scar formation in chronic discoid CLE. IL-22 activates STAT3 and it is emerging as a mediator with significant impact on normal wound repair, epidermal hyperproliferation and prevention of fibrosis. This work focussed on understanding the regulation and functional impact of IL-22 and IFNλ on skin cells. The counter-regulatory effect of IL-22 on the activities of IFNλ was assessed through downstream interferon stimulated genes (ISGs) expression in healthy and CLE keratinocytes. Cell proliferation and gap closure were investigated in skin resident cells using cell trace dye and scratch assay. Dermal fibroblasts were assessed for the presence of IFNλR1 and IL-22R1, downstream activities of the receptors. Results showed that IL-22 accelerated “scratch” closure in keratinocytes while IFNλ caused a delay in closure. IL-22 significantly downregulated IFNλ-induced chemokines expression in healthy, but not CLE keratinocytes. Reduced IL-22R1 expression and “STAT3 signature genes” was observed in CLE keratinocytes. A key finding of this project is that dermal fibroblasts respond to both IFNλ and IL-22. This work shows that IL-22 can reduce the damaging effect of IFNs in inflamed skin and also identifies dermal fibroblasts as important cells in skin immune responses. In conclusion, IL-10 family members can have both beneficial and destructive effects on the skin organ depending on the micro milieu and cell-type involved. Manipulating the balance of IL-10 family members in the skin may offer new therapeutic approach for both psoriasis and CLE.

京都大学 / 0048 / 新制・課程博士 / 博士(薬学) / 甲第18551号 / 薬博第813号 / 新制||薬||238(附属図書館) / 31451 / 京都大学大学院薬学研究科医療薬科学専攻 / (主査)教授 橋田 充, 教授 髙倉 喜信, 教授 佐治 英郎 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

Cutaneous lupus erythematosus (CLE) is an autoimmune disease that resolves with or without permanent scars depending on the subtype. Interferons (IFNs), including the skin specific IFNλ mainly activate STAT1, which results in inflammation in CLE and may play a significant role in scar formation in chronic discoid CLE. IL-22 activates STAT3 and it is emerging as a mediator with significant impact on normal wound repair, epidermal hyperproliferation and prevention of fibrosis. This work focussed on understanding the regulation and functional impact of IL-22 and IFNλ on skin cells. The counter-regulatory effect of IL-22 on the activities of IFNλ was assessed through downstream interferon stimulated genes (ISGs) expression in healthy and CLE keratinocytes. Cell proliferation and gap closure were investigated in skin resident cells using cell trace dye and scratch assay. Dermal fibroblasts were assessed for the presence of IFNλR1 and IL-22R1, downstream activities of the receptors. Results showed that IL-22 accelerated “scratch” closure in keratinocytes while IFNλ caused a delay in closure. IL-22 significantly downregulated IFNλ-induced chemokines expression in healthy, but not CLE keratinocytes. Reduced IL-22R1 expression and “STAT3 signature genes” was observed in CLE keratinocytes. A key finding of this project is that dermal fibroblasts respond to both IFNλ and IL-22. This work shows that IL-22 can reduce the damaging effect of IFNs in inflamed skin and also identifies dermal fibroblasts as important cells in skin immune responses. In conclusion, IL-10 family members can have both beneficial and destructive effects on the skin organ depending on the micro milieu and cell-type involved. Manipulating the balance of IL-10 family members in the skin may offer new therapeutic approach for both psoriasis and CLE. / University of Bradford and Centre for Skin Sciences

L’asthme est une maladie inflammatoire chronique des voies aériennes. Chez les individus sensibles, l’inhalation d’allergènes entraine une inflammation pulmonaire se traduisant par des épisodes récurrents de toux, de difficultés respiratoires et une sécrétion de mucus. Des études réalisées chez l’animal ont mis en évidence un rôle crucial des lymphocytes Th2 et des cytokines associées (IL-4, IL-5 et IL-13). Plus récemment, il a été montré que les lymphocytes Th17 participaient à la physiopathologie de l’asthme. La présente étude s’intéresse à une cytokine majoritairement produite par les Th17 : l’IL-22. Différents travaux indiquent que cette cytokine serait impliquée dans l’immunitémucosale où elle exercerait des effets protecteurs ou pro-inflammatoires en fonction du modèle expérimental étudié. En utilisant un modèle murin d’inflammation pulmonaire allergique induite par l’ovalbumine, nous avons montré que l’IL-22 jouait un rôle pro-inflammatoire au cours de l’induction de l’asthme allergique puisque les souris déficientes en IL-22 développent une forme atténuée de la maladie. A l’inverse, nous avons constaté que l’IL-22 avait un effet protecteur dans la phase effectrice, et que cet effet était dépendant de l’IL-17A. Nos travaux mettent donc en lumière une double fonction de l’IL-22 dans l’asthme allergique chez la souris. En parallèle de ce travail, nous nous sommes intéressés au rôle de l’IL-1 et de l’inflammasome NLRP3 dans ce même modèle d’inflammation pulmonaire. Enfin, une troisième étude a permis de mettre en lumière un rôle encore inconnu de l’interleukine-33 dans l’activation des cellules dendritiques au cours de la mise en place de la réponse asthmatique. / Asthma is a heterogenous inflammatory disorder of the airways characterized by chronic airway inflammation, airway hyper-reactivity and by symptoms of recurrent wheezing, coughing and shortness breath. Understanding of the role of allergy and Th2 cells in asthma has benefited from mouse model of allergic asthma. Recently, several studies highlighted Th17 involvement in asthma pathogenesis. In the present study, we investigate the role of IL-22, a Th17-related cytokine, in a mouse model of allergic lung inflammation induced by ovalbumin. First, using IL-22 deficient mice, we demonstrated a pro-inflammatory role of IL-22 during the sensitization phase. In contrast, we observed a protective function of IL-22 during the effective phase. This protective effect of IL-22 seems to be dependent of IL-17. In conclusion, we demonstrate here a dual role of IL-22 in asthma pathogenesis. Since interleukin-1_ is critical for Th17 polarization in human, we also investigated the role of IL-1 signalling and NLRP3 inflammasome in our model of allergic airway inflammation. We showed that NLRP3 inflammasome and IL-1R/IL-1 pathway are critical to induce allergic lung inflammation, even in the absence of adjuvant. Finally, we studied the effect of interleukin-33 on dendritic cells activation and Th2 priming during antigen sensitization and in established asthma.

Human γδ T cells expressing the Vγ2Vδ2 T cell antigen receptor play important roles in immune responses to microbial pathogens by monitoring prenyl pyrophosphate isoprenoid metabolites. Most adult Vγ2Vδ2 cells are memory cytotoxic cells that produce interferon-γ (IFN-γ). Recently, murine γδ T cells were found to be major sources of interleukin (IL)-17A in anti-microbial and autoimmune responses. To determine if primate γδ T cells play similar roles, we characterized IL-17A and IL-22 production by Vγ2Vδ2 T cells. IL-17A-producing memory Vγ2Vδ2 T cells exist at low but significant frequencies in adult humans (1:2,762 T cells) and at even higher frequencies in adult rhesus macaques. Higher levels of Vγ2Vδ2 T cells produce IL-22 (1:1,864 T cells) although few produce both IL-17A and IL-22. Unlike adult humans where many IL-17A+ V#947;2Vδ2 T cells also produce IFN-#947; (T#947;δ1/17), the majority of adult macaques IL-17A+ Vδ2 T cells (T#947;δ17) do not produce IFN-#947;. To define the cytokine requirements for T#947;δ17 cells, we stimulated human neonatal V#947;2Vδ2 T cells with the bacterial antigen, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate, and various cytokines and mAbs in vitro. We find that IL-6, IL-1β, and transforming growth factor-β (TGF-β) are required to generate T#947;δ17 cells in neonates whereas T#947;δ1/17 cells additionally required IL-23. In adults, memory T#947;δ1/17 and T#947;δ17 cells required IL-23, IL-1β, and TGF-β but not IL-6. IL-22-producing cells showed similar requirements. Both neonatal and adult IL-17A+ V#947;2Vδ2 T cells expressed elevated levels of retinoid-related orphan receptor-#947;t. Our data suggest that, like Th17 αβ T cells, V#947;2Vδ2 T cells can be polarized into T#947;δ17 and T#947;δ1/17 populations with distinct cytokine requirements for their initial polarization and later maintenance.

La voie de signalisation impliquant l’interleukine (IL)-22 a un rôle majeur dans le maintien des fonctions de barrière des surfaces exposées du corps humain. Elle est indispensable pour la promotion de l'immunité antimicrobienne épithéliale, de l'inflammation et de la réparation tissulaire. Des situations pathologiques impliquant une altération de cette voie de signalisation ont déjà été décrites, mais rarement au niveau pulmonaire. Ce travail étudie cette voie de signalisation dans trois pathologies respiratoires. Lors de la broncho-pneumopathie chronique obstructive, un excès de sécrétion de protéases à sérine secondaire au recrutement de neutrophiles est responsable d’une protéolyse du récepteur à l’IL-22. Cette protéolyse inhibe les mécanismes de défense épithéliale dépendante de l’IL-22. Lors d’infection pulmonaire à P. aeruginosa, un facteur de virulence sécrété par cette bactérie dégrade l’IL-22 et inhibe la sécrétion épithéliale de peptides antimicrobiens. Enfin, une surexpression du récepteur à l’IL-22 a été observée dans le cancer du poumon non à petites cellules. Cette surexpression est associée à une surmortalité. / The (interleukin) IL-22/IL-22 receptor (R) pathway is critical in the maintenance of barrier function at exposed surface of the body. This pathway is also essential to promote innate mucosal immunity, inflammation and tissue homeostasis. Dysregulation of IL-22/IL-22R pathway has been described in human diseases, but has been barely studied in respiratory pathologies. This work reveals three lung diseases with altered IL-22/IL-22R pathway. During chronic obstructive pulmonary disease, the proteolytic action of neutrophil-derived enzymes cleave the IL-22R and inhibit IL-22-mediated epithelial cell response. Next, we demonstrated that P. aeruginosa used its own proteolytic system to escape from host defenses through the proteolysis of IL-22 leading to negative regulation of antimicrobial peptides. Finally, we observed that higher IL-22R expression is correlated with squamous cell lung carcinoma and is associated with increase mortality.

Introdução: O objetivo deste trabalho foi caracterizar a composição da microbiota bucal e a formação e progressão de lesões periapicais induzidas experimentalmente em dentes de camundongos knockout para IL-22 (IL-22 KO) comparados com animais wild-type (WT). Material e Métodos: Inicialmente, foi realizada a avaliação do perfil microbiano da cavidade bucal dos animais (40 espécies de micro-organismos), no dia das exposições pulpares, por meio de técnica de biologia molecular (Checkerboard DNA-DNA hybridization). Em seguida, lesões periapicais foram induzidas nos primeiros molares inferiores dos camundongos e, decorridos os períodos de 7, 21 e 42 dias, os animais foram submetidos à eutanásia em câmara de CO2. As mandíbulas foram então removidas e submetidas ao processamento histotécnico. A seguir, cortes representativos de cada dente foram corados com hematoxilina e eosina (HE), para descrição do tecido pulpar e das regiões apical e periapical, em microscopia óptica convencional e mensuração da área das lesões periapicais em microscopia de fluorescência. Além disso, cortes sequenciais foram avaliados por meio de: histoenzimologia para a marcação de osteoclastos (TRAP), coloração de Brown & Brenn (para identificação de bactérias) e imunohistoquímica (para identificação de RANK, RANKL e OPG). Os escores da quantidade de células bacterianas, para cada uma das 40 espécies avaliadas, foram submetidos à analise estatística empregando o teste não-paramétrico de Mann-Whitney para amostras independentes, para comparação entre os grupos. Os resultados numéricos obtidos na análise morfométrica da área das lesões periapicais e do número de osteoclastos foram submetidos à análise estatística \"one-way\" ANOVA e pós-teste de Bonferroni. Para todas as análises foi adotado o nível de significância de 5%. Resultados: Em relação ao perfil microbiano encontrado na cavidade bucal dos animais, foi possível observar diferença estatisticamente siginificante entre os dois grupos de animais para 6 espécies bacterianas (p<0,05), sendo 5 dessas espécies mais encontradas nos animais WT e apenas 1 encontrada em maior quantidade nos animais IL-22 KO. Já em relação à análise microscópica, o grupo dos animais WT mostrou diferença estatisticamente significante entre 7 e 42 dias e entre 21 e 42 dias, com aumento progressivo no tamanho das lesões e no número de osteoclastos (p<0,05). No grupo dos animais IL-22 KO, houve um aumento do tamanho da lesão e do número de osteoclastos entre 7 e 21 dias, seguido de diminuição desses parâmetros entre 21 e 42 dias, com diferença significante (p<0,05) entre 7 e 21 dias. Além disso, na comparação entre os dois tipos de animais, foram encontradas diferenças significantes (p<0,05) em relação ao tamanho das lesões periapicais e ao número de osteoclastos aos 42 dias, sem diferenças em relação à localização de bactérias e imunohistoquímica. Conclusões: Esse estudo demonstrou diferenças na composição da microbiota bucal dos animais WT e IL-22 KO, o que pode ter influenciado na formação das lesões periapicais. Além disso, a ausência da IL-22 em camundongos interferiu na progressão das lesões periapicais, assim como no número de osteoclastos, sugerindo a participação da IL-22 na resposta imune e inflamatória do hospedeiro à infecção dos canais radiculares. / Introduction: The aim of this study was to evaluate the participation of the IL-22 on the formation and progression of experimentally induced periapical lesions in teeth of IL-22 knockout (IL-22 KO) compared to wild-type (WT) mice. Methods: Initially, it was performed the evaluation of the microbial profile present in the oral cavity of animals (40 bacterial species), on the day of pulpal exposures, by means of molecular biology technique (checkerboard DNA-DNA hybridization). Then, the periapical lesions were induced in the inferior first molars of the mice and, after the periods of 7, 21 and 42 days, the animals were euthanized in a CO2 chamber. The jaws were removed and subjected to histotechnical processing. The following sections were representative stained with hematoxylin and eosin (HE) for description of the pulp tissue, apical and periapical regions in conventional optical microscopy and measurement of the area of periapical lesions in fluorescence microscopy. Moreover, sequential specimens were evaluated through: histoenzimology for osteoclasts (TRAP) Brown & Brenn staining (for bacteria identification) and immunohistochemistry (for RANK, RANKL and OPG identification). The scores of the amount of bacterial cells, for each one of the 40 species assessed, were subjected to statistical analysis using the nonparametric Mann-Whitney test for independent samples for comparison between groups. The numerical results of the morphometric analysis of the area of the periapical lesions and the number of osteoclasts were subjected to statistical analysis one-way ANOVA and Bonferroni\'s post-test. For all the statistical analysis the significance level of 5% was adopted. Results: Regarding the microbial profile found in the oral cavity of the animals, it was observed statistically siginificant differences between the two groups of animals for 6 bacterial species (p<0.05), with 5 species showing higher levels in the WT group and only 1 specie found in higher levels in the IL-22 KO animals. Concerning the microscopical analysis, the group of WT mice showed a statistically significant difference between 7 and 42 days and between 21 and 42 days, with a gradual increase in the size of periapical lesions and number of osteoclasts (p<0.05). In the group of IL-22 KO animals, an increase in lesion size and number of osteoclasts between 7 and 21 days was observed, followed by a decrease of these parameters between 21 and 42 days, with significant differences between 7 and 21 days (p <0.05). Moreover, when comparing the two types of animals, significant differences were found (p <0.05) about to the size of periapical lesions and number of osteoclasts at 42 days, without differences in localization of bacteria and immunohistochemistry. Conclusions: This study showed differences in the composition of the oral microbiota of the two types of animals that may have influenced the progression of periapical lesions. Moreover, the absence of IL-22 in mice interfered with the progression of periapical lesions, as well as in the number of osteoclasts, suggesting the involvement of this cytokine in host\'s immune and inflammatory response to the infection of root canals.

A Análise de Acoplamentos Estatísticos é uma técnica computacional capaz de identificar resíduos importantes para a estrutura e função de proteínas em uma família por meio da quantificação de conservação posicional, correlação entre posições e identificação de grupos de resíduos correlacionados entre si. Neste trabalho, a análise de acoplamentos estatísticos foi implementada e aplicada ao estudo das proteínas tirosina fosfatases. Em conjunto com as proteínas tirosina quinases (PTKs), que adicionam um grupo fosforil a um resíduo de tirosina em uma proteína, as proteínas tirosina fosfatases (PTPs), que o removem, são responsáveis por diversos processos de sinalização celular. Elas são um caso de evolução convergente, onde um subgrupo (as proteínas tirosina fosfatases de baixo peso molecular) não apresenta homologia às chamadas PTPs \"clássicas\", capazes de defosforilar apenas resíduos de tirosina, e às fosfatases de especifidicade dupla, capazes de defosforilar também resíduos de serina e treonina, além de substratos não-protéicos. Em comum, as três subfamílias apresentam apenas o motivo CX5R, característico para todas as PTPs. Através do estudo das três subfamílias utilizando a análise de acoplamentos estatísticos, foi possível obter uma descrição detalhada de suas características conservadas e correlacionadas, relacionando-as ao conhecimento acumulado sobre proteínas tirosina fosfatases e a questões em aberto como a regulação por dimerização, a especificidade e mutações relacionadas a patologias. Foi possível também apresentar um método capaz de distinguir proteínas tirosina fosfatases de baixo peso molecular das arsenato redutases, derivadas das primeiras por evolução divergente. Adicionalmente, a técnica foi aplicada ao estudo das hexoquinases, às superóxido dismutases e às peroxidases. A tese descreve também estudos desenvolvidos pelo autor na área de cristalografia de proteínas a determinação das estruturas da Transtirretina humana em complexo com genisteína, da holo-Hexoquinase PI de S. cerevisae, do complexo IL-22/IL-22R1 e da Laminarinase de R. marinus. / The statistical coupling analysis is a computational technique which can identify important residues for the structure and function of proteins in a family by quantifying positional conservation, correlation between positions and identifying groups of self-correlating residues. Its implementation in this research group was applied to the study of the protein tyrosine phosphatases. Together with the protein tyrosine kinases (PTKs), which add a phosphoryl group to a tyrosine residue in proteins, the protein tyrosine phosphatases (PTPs), which remove it, are responsible for a variety of cell signaling processes. They are a case of convergent evolution, since one subgroup (the low molecular weight protein tyrosine phosphatases) are not homologous to the classical phosphatases, which can only dephosphorilate tyrosine residues, and the dual-specificity phosphatases, which can also dephosphorilate serine and threonine residues, and also non-proteinaceous substrates. All three sub-families have, in common, the CX5R motif, a characteristic of all PTPs. By applying the statistical coupling analysis to the study of the three sub-families, it was possible to obtain a detailed depiction of their conserved and correlated characteristics, relating them to the accumulated knowledge on protein tyrosine phosphatases and open questions such as protein regulation by dimerization, specificity and disease-related mutations. It was also possible to present a method to distinguish between low molecular weight phosphatases and arsenate reductases, which are derived by the former by divergent evolution. In addition, the technique was applied to the study of hexokinases, superoxide dismutases and peroxidases. The thesis also describe studies developed by the author in the field of protein crystallography the structure determination of human transthyretin in complex with genistein, holo-hexokinase PI from S. cerevisae, the IL-22/IL-22R1 complex and the laminarinase from R. marinus.

Introdução: O objetivo deste trabalho foi caracterizar a composição da microbiota bucal e a formação e progressão de lesões periapicais induzidas experimentalmente em dentes de camundongos knockout para IL-22 (IL-22 KO) comparados com animais wild-type (WT). Material e Métodos: Inicialmente, foi realizada a avaliação do perfil microbiano da cavidade bucal dos animais (40 espécies de micro-organismos), no dia das exposições pulpares, por meio de técnica de biologia molecular (Checkerboard DNA-DNA hybridization). Em seguida, lesões periapicais foram induzidas nos primeiros molares inferiores dos camundongos e, decorridos os períodos de 7, 21 e 42 dias, os animais foram submetidos à eutanásia em câmara de CO2. As mandíbulas foram então removidas e submetidas ao processamento histotécnico. A seguir, cortes representativos de cada dente foram corados com hematoxilina e eosina (HE), para descrição do tecido pulpar e das regiões apical e periapical, em microscopia óptica convencional e mensuração da área das lesões periapicais em microscopia de fluorescência. Além disso, cortes sequenciais foram avaliados por meio de: histoenzimologia para a marcação de osteoclastos (TRAP), coloração de Brown & Brenn (para identificação de bactérias) e imunohistoquímica (para identificação de RANK, RANKL e OPG). Os escores da quantidade de células bacterianas, para cada uma das 40 espécies avaliadas, foram submetidos à analise estatística empregando o teste não-paramétrico de Mann-Whitney para amostras independentes, para comparação entre os grupos. Os resultados numéricos obtidos na análise morfométrica da área das lesões periapicais e do número de osteoclastos foram submetidos à análise estatística \"one-way\" ANOVA e pós-teste de Bonferroni. Para todas as análises foi adotado o nível de significância de 5%. Resultados: Em relação ao perfil microbiano encontrado na cavidade bucal dos animais, foi possível observar diferença estatisticamente siginificante entre os dois grupos de animais para 6 espécies bacterianas (p<0,05), sendo 5 dessas espécies mais encontradas nos animais WT e apenas 1 encontrada em maior quantidade nos animais IL-22 KO. Já em relação à análise microscópica, o grupo dos animais WT mostrou diferença estatisticamente significante entre 7 e 42 dias e entre 21 e 42 dias, com aumento progressivo no tamanho das lesões e no número de osteoclastos (p<0,05). No grupo dos animais IL-22 KO, houve um aumento do tamanho da lesão e do número de osteoclastos entre 7 e 21 dias, seguido de diminuição desses parâmetros entre 21 e 42 dias, com diferença significante (p<0,05) entre 7 e 21 dias. Além disso, na comparação entre os dois tipos de animais, foram encontradas diferenças significantes (p<0,05) em relação ao tamanho das lesões periapicais e ao número de osteoclastos aos 42 dias, sem diferenças em relação à localização de bactérias e imunohistoquímica. Conclusões: Esse estudo demonstrou diferenças na composição da microbiota bucal dos animais WT e IL-22 KO, o que pode ter influenciado na formação das lesões periapicais. Além disso, a ausência da IL-22 em camundongos interferiu na progressão das lesões periapicais, assim como no número de osteoclastos, sugerindo a participação da IL-22 na resposta imune e inflamatória do hospedeiro à infecção dos canais radiculares. / Introduction: The aim of this study was to evaluate the participation of the IL-22 on the formation and progression of experimentally induced periapical lesions in teeth of IL-22 knockout (IL-22 KO) compared to wild-type (WT) mice. Methods: Initially, it was performed the evaluation of the microbial profile present in the oral cavity of animals (40 bacterial species), on the day of pulpal exposures, by means of molecular biology technique (checkerboard DNA-DNA hybridization). Then, the periapical lesions were induced in the inferior first molars of the mice and, after the periods of 7, 21 and 42 days, the animals were euthanized in a CO2 chamber. The jaws were removed and subjected to histotechnical processing. The following sections were representative stained with hematoxylin and eosin (HE) for description of the pulp tissue, apical and periapical regions in conventional optical microscopy and measurement of the area of periapical lesions in fluorescence microscopy. Moreover, sequential specimens were evaluated through: histoenzimology for osteoclasts (TRAP) Brown & Brenn staining (for bacteria identification) and immunohistochemistry (for RANK, RANKL and OPG identification). The scores of the amount of bacterial cells, for each one of the 40 species assessed, were subjected to statistical analysis using the nonparametric Mann-Whitney test for independent samples for comparison between groups. The numerical results of the morphometric analysis of the area of the periapical lesions and the number of osteoclasts were subjected to statistical analysis one-way ANOVA and Bonferroni\'s post-test. For all the statistical analysis the significance level of 5% was adopted. Results: Regarding the microbial profile found in the oral cavity of the animals, it was observed statistically siginificant differences between the two groups of animals for 6 bacterial species (p<0.05), with 5 species showing higher levels in the WT group and only 1 specie found in higher levels in the IL-22 KO animals. Concerning the microscopical analysis, the group of WT mice showed a statistically significant difference between 7 and 42 days and between 21 and 42 days, with a gradual increase in the size of periapical lesions and number of osteoclasts (p<0.05). In the group of IL-22 KO animals, an increase in lesion size and number of osteoclasts between 7 and 21 days was observed, followed by a decrease of these parameters between 21 and 42 days, with significant differences between 7 and 21 days (p <0.05). Moreover, when comparing the two types of animals, significant differences were found (p <0.05) about to the size of periapical lesions and number of osteoclasts at 42 days, without differences in localization of bacteria and immunohistochemistry. Conclusions: This study showed differences in the composition of the oral microbiota of the two types of animals that may have influenced the progression of periapical lesions. Moreover, the absence of IL-22 in mice interfered with the progression of periapical lesions, as well as in the number of osteoclasts, suggesting the involvement of this cytokine in host\'s immune and inflammatory response to the infection of root canals.