NKp46- and IL-10-dependent silencing of NK cell-mediated IFN-gamma production upon cross talk with tolerogenic dendritic cells

DAMIAN EZEQUIEL AVILA; LUCAS EZEQUIEL ROSSI; CAROLINA INES DOMAICA; RAUL GERMAN SPALLANZANI; ANDREA ZIBLAT; GABRIEL ADRIAN RABINOVICH; NORBERTO WALTER ZWIRNER

Ciudad Autonoma de Buenos Aires, Argentina

Congreso; 1º Congreso Franco-Argentino de Inmunología, LVIII Reunión Anual de la Sociedad Argentina de Inmunología, XIII Jornada Científica del Grupo Rioplatense de Citometría de Flujo y 3º Jornadas Argentinas de Inmunodeficiencias Primarias; 2010

Sociedad Argentina de Inmunología y Sociedad Francesa de Inmunología

Cross talk between mature dendritic cells (mDCs) and NK cells through the cell surface receptors NKp30 and DNAM-1 and the cytokines IL-12, IL-15, IL-18 and IFN-γ results in a reciprocal activation of both cells. However, the outcome of the cross talk between tolerogenic DCs (tDCs) and NK cells, which may take place within a tumor microenvironment where tDCs are abundant, remains unknown. Previously, we observed that tDCs prevent IFN-γ secretion by NK cells in a mechanism involving cell surface receptors and soluble factors. Thus, the objective of this study was to elucidate the mechanisms underlying such NK cell effector function silencing promoted by tDCs. Human tDCs were generated from monocyte-derived DCs treated with LPS+dexamethasone and indentified as CD1a+MHC-II+CD14-CD86low and IL-12lowIL-10high. Upon co-culture with NK cells for 24h, we observed that extensively washed tDCs (but not mDCs) prevented IFN-γ secretion by NK cells (202±88pg/ml vs. 1105±502pg/ml; p<0.001). Inhibition of IFN-γ secretion was not due to DC-induced NK cell apoptosis, as total apoptosis of NK cells after co-culture with iDCs, mDCs or tDCs were -3.9±5.3%, 14.4±6.0% and 4.4±5.6%, respectively over basal levels (NK cells alone). To investigate the receptors involved in this response, we performed blocking assays with anticytokine and anti-NK cell receptor mAbs. Blockade of IL-10 and, unexpectedly, blockade of the activating receptor NKp46 (but not NKp30, NKp44 or NKG2D) restored the ability of NK cells to secrete IFN-γ upon co-culture with tDCs (871,8±343,5pg/ml and 1072±427,1pg/ml vs. 273,7±205, 4pg/ml, respectively; p<0.05 in each case). Thus, tDCs preclude NK cell IFN-γ secretion through IL-10 production and promote a previously unrecognized inhibitory signal through NKp46. Our findings unravel a novel immunosuppressive mechanism of possible relevance within a tumor milieu and could be relevant as tolerogenic mechanism for NK cells to avoid self attack during autoimmunity.