G-CSF-Induced Suppressor IL-10+ Neutrophils Promote Regulatory T Cells That Inhibit Graft-Versus-Host Disease in a Long-Lasting and Specific Way.

Acute graft-versus-host disease (aGVHD) is the main complication of allogeneic hematopoietic stem cell transplantation, and many efforts have been made to overcome this important limitation. We showed previously that G-CSF treatment generates low-density splenic granulocytes that inhibit experimental aGVHD. In this article, we show that aGVHD protection relies on incoming IL-10+ neutrophils from G-CSF-treated donor spleen (G-Neutrophils). These G-Neutrophils have high phagocytic capacity, high peroxide production, low myeloperoxidase activity, and low cytoplasmic granule content, which accounts for their low density. Furthermore, they have low expression of MHC class II, costimulatory molecules, and low arginase1 expression. Also, they have low IFN-γ, IL-17F, IL-2, and IL-12 levels, with increased IL-10 production and NO synthase 2 expression. These features are in accordance with the modulatory capacity of G-Neutrophils on regulatory T cell (Treg) generation. In vivo, CD25+ Treg depletion shortly after transplantation with splenic cells from G-CSF-treated donors blocks suppression of aGVHD, suggesting Treg involvement in the protection induced by the G-Neutrophils. The immunocompetence and specificity of the semiallogeneic T cells, long-term after the bone marrow transplant using G-Neutrophils, were confirmed by third-party skin graft rejection; importantly, a graft-versus-leukemia assay showed that T cell activity was maintained, and all of the leukemic cells were eliminated. We conclude that G-CSF treatment generates a population of activated and suppressive G-Neutrophils that reduces aGVHD in an IL-10- and Treg-dependent manner, while maintaining immunocompetence and the graft versus leukemia effect.

Efeito protetor da terapia combinada de indução de tolerância oral e tratamento probiótico do doador na Doença Enxerto contra Hospedeiro aguda / [ Protective effect of combined oral tolerance induction therapy and probiotic donor treatment in acute Graft versus Host Disease]

A maior limitação do transplante de células-tronco hematopoiético alogeneico (TCTHa) é a doença enxerto contra hospedeiro (DECH), uma resposta mediada por células T, que está intimamente associada ao efeito benéfico enxerto contra leucemia (ECL). As terapias utilizadas no tratamento da DECH são comumente baseadas na administração de imunossupressores não-específicos, resultando e inúmeras complicações clínicas e inibição do efeito ECL nos pacientes transplantados. Neste trabalho propomos uma abordagem alternativa baseada na indução de tolerância oral com proteínas do receptor em doadores de um transplante semialogeneico, associado à ingestão da bactéria probiótica Lactococcus lactis, utilizada aqui como um adjuvante da tolerância (terapia combinada). O tratamento dos doadores com a terapia combinada previamente ao transplante protegeu os receptores das manifestações clínicas e patológicas da doença, resultando em 100% de sobrevida e ainda foi capaz de manter o efeito enxerto contra leucemia. A proteção é específica, duradoura e dependente da atividade de células B IL-10 suficientes, as quais são capazes de induzir células Treg no receptor. Esses dados sugerem que a terapia combinada representa uma estratégia promissora na prevenção da DECH, mas com a preservação da ECL, abrindo novas possibilidades para o tratamento de pacientes humanos que serão submetidos ao TCTHa. (AU)

The major limitation of allogeneic hematopoietic stem cell transplantation (aHSCT) is graftversus-host disease (GVHD), a T cell-mediated response that is closely related to the benefic graft versus leukemia reaction (GVLr). Therapy for GVHD is commonly based on nonspecific immunosupression of the transplant recipient, resulting in several clinical complications and inhibition of GVLr. Here we propose an alternative approach based on induction of oral tolerance to the recipient antigens in a semiallogenic transplant donors, associated with intake of probiotic Lactococcus lactis as tolerogenic adjuvant (combined therapy). We show that treatment of donor mice with combined therapy before the transplant protects the recipients from clinical and pathological manifestations of disease, resulting in 100% survival rates and maintenance of GVLr. The protection is specific, long lasting and dependent on donor B IL-10 sufficient cells activity, which induces regulatory T cells in the host. These data suggest that combined therapy is a promising strategy for prevention of GVHD with preservation of GVL, opening new possibilities to treat human patients subjected to allogeneic aHSCT. (AU)