MYELOID-DERIVED SUPPRESSOR CELLS EXPANDED BY ORAL YERSINIA ENTEROCOLITICA INFECTION MEDIATE THEIR IMMUNOSUPPRESSIVE ACTIVITY THROUGH A NITRIC OXIDE-DEPENDENT MECHANISM

MARIANELA LEPORATI; ROBERTO DAVICINO; JAVIER ELIÇABE; SILVIA DI GENARO

Mar del Plata

Congreso; LXVI Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2018

Myeloid-derived suppressor cells (MDSC) represent a heterogeneous population of largely immature myeloid cells endowed with a robust immunosuppressive activity. Yersinia enterocolitica (Ye) are Gram-negative bacteria that cause food-borne gastrointestinal diseases. The role MDSCs in host-pathogen interactions has been poorly defined. In previous studies we demonstrated that oral Ye infection of mice induces MDSCs expansion in intestine and spleen. However, the mechanisms of MDSC immunosuppressive activity in Ye infection has not been defined. The purpose of this work was to analyse the mechanism by which MDSC exert their suppressive activity in this infection. Therefore, C57BL/6 mice were orally infected with Ye WAP-314 serotype O:8. On days 5, 10 and 20 post-infection (p.i), cellular infiltration in mesenteric lymph nodes (MLN), Peyer´s patches (PP) and spleen was analysed. Suppressive activity on cell proliferation was determined by MTT assay, and nitrite levels were measured with Griess reagent. After in vitro iNOS inhibition with Aminoguanidine (AG), arginase 1 activity was indirectly determined by colorimetric quantification of urea. We found that Ye-infected mice increased the frequencies of CD11b+Gr-1+ cells in PP, MLN and spleen on days 5, 10 and 20 p.i (p