Activated NK cells reprogram regulatory dendritic cells into mature dendritic-like cells

TORRES, NICOLÁS IGNACIO; RAFFO IRAOLAGOITÍA, XIMENA LUCÍA; ZIBLAT, ANDREA; SPALLANZANI, RAÚL GERMÁN; DOMAICA, CAROLINA INÉS; FUERTES, MERCEDES BEATRIZ; ZWIRNER, NORBERTO WALTER

Mar del Plata

Congreso; 62a Reunión Anual de la Sociedad Argentina de Inmunología; 2014

Sociedad Argentina de Inmunología

Reciprocal crosstalk between dendritic cells (DC) and NK cells plays an essential role during the immune responses against tumors. In addition, tumors promote the recruitment of regulatory dendritic cells (regDC), which contributes to immune escape. regDC also have been involved in the maintenance of immune tolerance. Previously, we demonstrated that regDC restrain NK cell activation through an NKp46-mediated regulatory mechanism. However, the consequences of the crosstalk between regDC and activated NK cells remain unknown. Thus, the aim of this work was to explore the outcome of such crosstalk using murine NK cells stimulated with agonists TLRs and IL-12. We obtained immature DC (iDC) from bone marrow cells differentiated for 6 days with GM-CSF. To obtain mature DC (mDC) and regDC, iDC were stimulated overnight with 25ng/ml of LPS (mDC) or 25ng/ml of LPS and 100nM of dexamethasone (regDC). We observed that regDC induced a ten-fold reduction in proliferation of allogeneic splenocytes as compared with mDC (p<0.05). Flow cytometry analyses revealed that co-culture of regDC with NK cells pre-stimulated overnight with IL-12 and polyI:C (a TLR3 agonist), but not IL-12 alone, polyI:C alone or Loxoribine (a TLR7 agonist) alone or in combination with IL-12, induced and up-regulation of the activation markers MHC-II and CD86, suggesting that NK cells activated with IL-12 and polyI:C partially reverted the regulatory phenotype of regDC. Moreover, these regDC pre-cultured with NK cells previously stimulated with IL-12 and polyI:C, but not regDC cultured with NK cells previously stimulated with IL-12 alone, Loxoribine or IL-12 and Loxoribine stimulated the proliferation of naïve allogeneic splenocytes up to values comparable to mDC (p<0.05). Therefore, we conclude that NK cells stimulated with polyI:C and IL-12 acquire the ability to revert the phenotype and stimulatory function of regDC, which might be relevant in the formulation of novel anti-cancer therapies.