Brucella abortus RNA contributes to the down-modulation of MHC-II expression on monocytes/macrophages diminishing CD4+ T cell responses.

MILILLO MA; TROTTA A; SERAFINO A; MARÍN FRANCO JL; MARINHO FV; ALCAIN J; GENOULA M; BALBOA L; COSTA OLIVEIRA S; GIAMBARTOLOMEI GH; BARRIONUEVO P

San Miguel de Tucumán

Congreso; LXVII Reunión Anual de la Sociedad Argentina de Inmunología (SAI).; 2019

In order to persist inside the host, B. abortus must trigger different strategies to evade the adaptive T cell response. Previously, we demonstrated that B. abortus inhibits the IFN-γ-induced MHC-II surface expression on human monocytes. Consequently, the infected macrophages show a diminished antigen presentation to TCD4+ lymphocytes. B. abortus outer membrane lipoproteins -bacterial structural components- are involved in MHC-II down-modulation through IL-6 secretion. Nevertheless, this phenomenon was less marked than that observed in the infection. This led us to think that there should have been another component associated to live bacteria implicated in MHC-II down-modulation. Actually, we have recently showed that B. abortus RNA, a PAMP associated to bacterial viability (vita-PAMP), is responsible for MHC-I down-modulation. Thus, the aim of this study was to analyse whether B. abortus RNA could also contribute to MHC-II down-modulation. For this, human monocytic THP-1 cells were incubated with B. abortus RNA in the presence of IFN-γ for 48 h. MHC-II expression (HLA-DR) was evaluated by flow cytometry. B. abortus RNA significantly (p