(A) RAW264.7 macrophages were mock-infected (control) or infected (MOI=5) with type I, type I Δrop16 or type II parasites and 24 h later arginase activity was determined (Student t *P value < 0.05, type I vs. type I Δrop16 or type II). Error bars = + SD.
(B) As in A, except the macrophages were fixed and stained with antibodies to the parasite surface antigen SAG-1 (green) and the M2 markers CD206 or mMgl. Hoechst dye was used to stain nuclei (blue).
(C) Western blot using antibodies against mMgl1/2, tyrosine phosphorylated STAT6 (pSTAT6) or total STAT6. Antibodies against GAPDH and SAG-1 were used for host cell and parasite loading controls, respectively.
(D) One day after infection with the indicated strain types, macrophages were fixed, permeabilized and stained with antibodies against pSTAT6 and SAG-1. Nuclei were stained with Hoechst (blue).
(E) BMDMs were infected with GFP expressing type I or type I Δrop16 parasites and stained with PE labeled antibodies to the surface receptors B7-H1 (PD-L1), B7-DC (PD-L2), Dectin-1 (Clec7a) or CD86 (which is not regulated by ROP16). Histogram plots depicting the relative surface expression of these markers on infected GFP+ (black lines) and non-infected GFPneg (blue lines) BMDMs in the same well. Isotype staining with Rat IgG2a antibodies is also shown (shaded histogram).
(F) BALB/c mice were infected i.p. with type I, type I Δrop16 or type II parasites. Twenty-one h post-infection, PECs were harvested and stained for CD11b and the SAG-1 parasite surface antigen. Infected (toxo+) and uninfected (toxoneg) CD11b+ PECs were analyzed for their expression of pSTAT6 or CD206 by histogram (gray = ‘minus one’ staining control where cells are stained with all staining reagents except the anti-STAT6 or CD206 primary antibodies; red = type I; blue = type II; green = type I Δrop16; black = PECs from an uninfected mouse stimulated with recombinant murine IL-4 for 10 minutes at 37°C). Data are representative of 2 independent experiments (n=3).
(G) Bar graphs depict the percentage of positively staining CD11b+ PECs as analyzed in F (‘KO’= type I Δrop16). N.D.= not detected. Error bars = + SD. ANOVA one-way analysis of variance was used to determine statistical significance. The percentage of infected CD11b+ cells was similar in type I, type II, and type I Δrop16 infected mice (data not shown).
See for a list of genes regulated by ROP16, as well as for a TFBS analysis of this gene set.