Rapamycin Augments Human DC IL-12p70 and IL-27 Secretion to Promote Allogeneic Type1 Polarization Modulated by NK Cells

Abstract

Mammalian target of rapamycin kinase inhibitor (mTORi) rapamycin (RAPA) use in transplantation can lead to inflammatory complications in some patients. Our goal was to better understand how mTORi-exposed human monocyte-derived dendritic cells (DC) stimulated with pro-inflammatory cytokines shape T cell allo-immunity. RAPA-conditioned-DC (RAPA-DC) displayed a more immature phenotype than untreated, control (CTRL)-DC. However, subsequent exposure of RAPA-DC to an inflammatory cytokine cocktail (ICC) plus IFN-γ induced a mature Type-1 promoting phenotype, consisting of elevated HLA-DR and co-stimulatory molecules, augmented IL-12p70 and IL-27 production, but decreased IL-10 secretion compared to CTRL-DC. Co-culture of mature (m) RAPA-DC with allogeneic peripheral blood mononuclear cells resulted in significantly increased Type-1 (IFN-γ) responses by T cells. Moreover, NK cells acted as innate modulators that conveyed activating cell-to-cell contact signals in addition to helper (IFN-γ) and/or regulatory (IL-10) soluble cytokines. We conclude that production of IL12-p70, IL-27, and low IL-10 by RAPA-DC allowed us to elucidate how these cytokines as well as NK-DC interaction shapes T cell allo-immunity. Thus, lack of inhibitory NK cell function during allo-specific T cell activation by human ICC+IFN-γ-stimulated RAPA-DC may represent an unwanted effector mechanism that may underlie RAPA-induced inflammatory events in transplant patients undergoing microbial infection or allograft rejection.

Evolving Perspectives of mTOR Complexes in Immunity and Transplantation

“…In a recent study, Macedo et al (72) found that while RAPAtreated cDC generated from healthy volunteers displayed an ''immature'' phenotype, subsequent exposure to an inflammatory cytokine cocktail plus IFN-g induced a mature, type-1-promoting, immunostimulatory phenotype. This was characterized by elevated cell surface HLA-DR and co-stimulatory molecules, augmented IL12p70 and IL-27 production and decreased IL-10 secretion.…”

Reparixin, a CXCR1/2 inhibitor in islet allotransplantation

“…22 It has been reported that in response to increased levels of IL-12p70, natural killer cells release large amounts of IFN-g and nitric oxide. 22,23 This undesirable induction has been shown with the use of rapamycin as an immunosuppressant, but was not seen with reparixin in this study. 23 Since reparixin is involved in the activation of CXCR1/2 and neutrophil recruitment, one additional cytokine that may be important to measure is the neutrophil activating factor IL-8, a mediator of both cytokine cascades and neutrophil responses.…”

“…22,23 This undesirable induction has been shown with the use of rapamycin as an immunosuppressant, but was not seen with reparixin in this study. 23 Since reparixin is involved in the activation of CXCR1/2 and neutrophil recruitment, one additional cytokine that may be important to measure is the neutrophil activating factor IL-8, a mediator of both cytokine cascades and neutrophil responses. 21 The KC receptor and the IL-8 type B receptor are homologous and mouse KC also known as CXCL1, neutrophil-activating protein 3 (NAP-3) is involved in chemotaxis and cell activation of neutrophils.…”

MyD88-silenced dendritic cells induce T-cell hyporesponsiveness and promote Th2 polarization in vivo

“…In addition, absence of MyD88 signaling resulted in reduced mRNA expression of IL-1 family cytokines [14]. IL-1 was not required for the growth of established human Th1 or Th2 clones, but it played a critical role in the development of Th2 cells, whereas Th1 development was unaffected [23]. Decrease of IL-1 family cytokines will also affect Th17 development.…”

“…Release of IL-12 by DCs promotes Th1 cells, which produce high levels of IFN-g and IL-2. Th2 cells are stimulated through OX40 ligation by DCs, and produce IL-4, IL-5 and IL-13 [23,24]. Tumor-growth factor-b (TGF-b), IL-1 and IL-6 induce the production of Th17, which is characterized by the production of IL-17A, IL-17F, IL-8, IL-21 and IL-22.…”