M2 macrophages inhibit IFN- production of NK cells through TGF- and NK cell-mediated cytotoxicity through cell-to-cell contact

NÚÑEZ, SOL YANEL; ZIBLAT, ANDREA; SECCHIARI, FLORENCIA; TORRES, NICOLÁS IGNACIO; SIERRA, JESSICA MARIEL; ARAYA, ROMINA ELIZABETH; RAFFO IRAOLAGOITÍA, XIMENA LUCÍA; DOMAICA, CAROLINA INÉS; FUERTES, MERCEDES BEATRIZ; ZWIRNER, NORBERTO WALTER

Mar del Plata

Congreso; 64a Reunión Anual de la Sociedad Argentina de Inmunología; 2016

Sociedad Argentina de Inmunología

Macrophages are highlyplastic cells that can modify their functional response according to thesurrounding microenvironment, becoming pro-inflammatory (M1) or anti-inflammatory(M2) macrophages. The outcome of the crosstalk between M1 and NK cells is well establishedplaying a critical role in the protection against infections and tumor growth.However, the effect of M2 on NK cells is less clear. We previously demonstratedthat M2 macrophages inhibit NK cell degranulation (n=8, p<0,001) andcytotoxicity (n=6, p<0,0001) against tumor cells andalso IFN-g secretion upon stimulation withcytokines (assessed by flow cytometry and ELISA, n=6, p<0,001)compared to M1. Thus, the aim of this work was to investigate the underlyingmechanisms involved in this inhibition. Accordingly, we used co-cultures ofhuman NK cells with M1 or M2 in vitropolarized macrophages. Human monocytes were differentiated to unpolarizedmacrophages (M0) with M-CSF for 6 days and then exposed overnight to LPS andIFN-g or IL-4 to obtain M1 andM2 respectively. Then isolated NK cells (resting or stimulated with IL-12,IL-15 and IL-18) were co-cultured overnight with M1 or M2 cells. Transwell experimentsand NK cell culture with M1 or M2 conditioned media demonstrated that theinhibition of IFN-g secretion was due tosoluble factors while inhibition of degranulation required contact between therespective cell types. Blockade of the immunosuppressive cytokine TGF-β in M2 macrophage-conditioned media restored the IFN-g secretion by NK cells (n<6,p<0,001) but blockade of TGF-β during co-cultures had no effect on NK cell degranulation(n=4, p>0,05), indicatingthat TGF-β is involved in silencingIFN-g secretion but not NKcell-mediated cytotoxicity. Therefore, we conclude that M2 negatively regulateNK cell IFN-g production throughsecretion of TGF-b but negatively regulateNK cell-mediated cytotoxicity through the interaction between cognatereceptor-ligands expressed by these cells.