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

Abstract

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.

Neutrophil, quo vadis?

“…Concomitantly, this understanding raises new questions regarding the extent of neutrophil diversity and the definition of unique neutrophil subsets in health, in cancer, and in other diseases. Indeed, neutrophil diversity in cancer is not an isolated phenomenon, and neutrophil subpopulations were also observed in other mouse models of disease, including infection [14], angiogenesis [15], and graft versus host disease [16]. Importantly, various neutrophil populations were identified in various human clinical conditions, including HIV-1 infection [17], sepsis [18], psoriasis [19], malaria [20], periodontal disease [21], lupus [22], and others.…”

Neutrophils Plasticity: The Regulatory Interface in Various Pathological Conditions

“…In terms of GVHD, it is important to point that protection was long-lasting and specific, keeping the immunocompetence to reject the skin grafts from third-party mice and rejecting the leukemic cells, keeping the GVL effect. These results show that neutrophils instruct T cells toward a specific tolerant state [37].…”

“…GVHD protection showing high mortality rates and poor clinical scores. This evidences that IL-10 + neutrophils are the agents of protection [37].…”

“…In a murine model of graft versus host disease (GVHD), the main limitation of stem cell transplantation, LDGs prevented 100% mortality [31]. These cells were better characterized recently [37] and will be described at the end of this chapter.…”

“…In murine models, several studies have shown that neutrophils produce IL-10 in response to a variety of infections, such as S. aureus [38], Candida albicans [40], Trypanssoma cruzi [41], and in inflammatory conditions, such as post-burn [42] and after G-CSF treatment [37]. However, these data are still a matter of conflict in the literature since just a few studies show the same phenotype in humans [43][44][45] and others were incapable to reproduce it [46,47].…”