Leishmania donovani promotes macrophages polarization towards M2 phenotype in vitro: A new approach to identify a new therapeutic target

Background: The immune response against L. donovani depends significantly on infected macrophages. Since Leishmania amastigotes deploy several immune suppressive mechanisms to escape host immune responses, macrophages polarize towards the classically activated macrophages (M1) or the alternatively activated macrophages (M2). The balance between both types is crucial in shaping the infection outcome. Objective: The aim of this study is to explore the macrophage polarization behavior in response to L. donovani infection, and to examine the differential expression of IL-10 and TNF-α by each phenotype. Material and Methods: Leishmania -infected phorbol 12-myristate 13-acetate (PMA)-treated human leukemia monocytic cell line (THP-1) was used as an in vitro model of Leishmania infection. Leishmania stationary phase promastigotes were used to infect the macrophages at different multiplicities of infections (MOIs) i.e., ratio of macrophages to stationary phase promastigotes at 1:1, 1:10, and 1:20; and time points of 24 and 48 h post infection (PI). While CD68, CD40, HLA-DR were used as markers for M1; CD68 and CD163 were used to characterize