FIG. 1.

Acute infection with the high-virulence (RA) T. cruzi strain downregulates or inhibits MHC class II expression on professional APC. Flow cytometry profiles of I-eK (MHC class II) molecules expressed on splenic DC (A), peritoneal macrophages (B), and B cells (C) from mice acutely infected with the RA strain (black line) or K98 strain (dark gray line) or controls (light gray). Enriched splenic DC suspensions were simultaneously stained with anti-CD11c-PE (for DC) and anti-I-eK-FITC. Peritoneal cells were simultaneously stained with anti-Mac-3-PE (for peritoneal macrophages) and anti-I-eK-FITC. Splenic cell suspensions were simultaneously stained with anti-CD19-PE (for B cells) and anti-I-eK-FITC. CD11c⁺, Mac-3⁺, and CD19⁺ events were analyzed for I-eK expression. The mean fluorescence obtained after staining with the corresponding isotype-matched monoclonal antibody was <10. Results of one representative experiment out of five are shown.