Mecanismos da modulação da expressão de MHC II e CD86 em células dendríticas pela DNAK e a diminuição da rejeição em transplantes de pele

• Ano de defesa: 2015
• Autor(a) principal: Borges, Thiago de Jesus
• Orientador(a): Bonorino, Cristina Beatriz C.
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul
• Programa de Pós-Graduação: Programa de Pós-Graduação em Biologia Celular e Molecular
• Departamento: Faculdade de Biociências
• País: Brasil
• Palavras-chave em Português: BIOLOGIA CELULAR; BIOLOGIA MOLECULAR; CÉLULAS DENDRÍTICAS; TRANSPLANTE DE PELE
• Área do conhecimento CNPq: CIENCIAS BIOLOGICAS::BIOLOGIA GERAL
• Link de acesso: http://tede2.pucrs.br/tede2/handle/tede/6461

Dendritic cells (DCs) are the major antigen-presenting cells. They provide three main signals to fully activate T cells. Signal one is when the complex peptide:MHC (p:MHC) expressed by DC is recognized by T cell receptor; signal two is the expression of co-stimulatory molecules from the B7 family (CD80 and CD86). The third signal consists in the cytokines produced by DCs, which will bias the quality of T cell response. Once one of this signal is blocked/interrupted, T cells are not fully activated. T cells are involved in the eradication of pathogens, but also in the pathogenesis of several disorders and, strategies that modulate signal two are being used to treat these disorders. Novel therapies that inhibit the second signal (checkpoint blockade) or T cell modulation by these molecules have being used/tested to manage tumors, autoimmune disorders and transplant rejection. Our group demonstrated that the M. tuberculosis protein DnaK (prokaryote Hsp70) has an immunosuppressive role on DCs, and can suppress rejection in a murine skin allograft model. Nevertheless, the molecular mechanism involved in this response need to be further elucidated. In the present work, we demonstrated that the treatment of murine DC with DnaK could decrease the basal levels TNF-α, IFN-γ and MCP-1 produced by these cells. This modulation was concomitant with a downregulation of the transcription factors C/EBPβ and C/EBPδ in a TLR2-ERK-STAT3-IL-10-dependent way. Beyond the signal three, DnaK could also downregulate the expression of MHC II (signal one) and CD86 (signal theree) on DCs, through the induction of a molecule called MARCH1. We developed an-situ treatment of skin grafts with DnaK prior the transplant. We observed that this treatment prolongs allograft survival with a decreased alloimmunity, and this dependent on MARCH1. The molecular pathway TLR2-ERK-STAT3-IL-10 was required for MARCH1 induction by DnaK. Moreover, we found that DnaK modulates a specific skin migratory DC – the CD103+ DCs. This is the major subset involved in skin allograft rejection. We tested in which innate receptors DnaK could bind and found that DnaK could not bind directly on TLR2, but in the LOX-1 and Siglec-E receptor, in a LOX-1/Siglec-E/TLR2 complex. Finally, from the data obtained we patented a new formulation and method to treat allografts prior the transplantation. Thus, DnaK tolerizes dendritic cells through the modulation of the three signals required to activate T cells. We believe that consists an innovative strategy to treat inflammatory disorders, rejection, asthma and sepsis.