B henselae–infected DCs express maturation markers and induce T-cell proliferation. (A) FACS analysis of CD83, CD80, CD86, CCR7, and MHC II (MHC DR) on DCs either left untreated or infected with B henselae (ratio 10:1 B. henselae/DCs) or treated with LPS (100 ng/mL; LPS-DCs) for 24 hours. Percentage of positive cells and mean of fluorescence intensity (in parentheses) is reported in each panel. Data shown are representative of 3 independent experiments. Indicated markers' staining (thick line) are presented in comparison with matched-isotype antibodies (thin line). (B) Cytospin preparations of DCs infected with B henselae were stained with CD208 monoclonal antibody. A strong cytoplasmic reactivity in the form of large paranuclear dots is evident in the majority of cells. Immunoperoxidase technique for anti-CD208 counterstained with hematoxylin. Original magnification × 200. Shown is 1 representative experiment of 3 performed. (C) Mixed leukocyte reaction using different concentrations of irradiated immature DCs (iDCs), LPS-matured DCs (LPS-mDCs), or B henselae–infected DCs (B. henselae–DCs) cocultured with 2 × 10⁵ allogeneic purified T cells. Proliferation was assayed as uptake of [H³] thymidine added in the last 16 hours of a 6-day culture assay. Results are expressed as mean counts per minute (cpm) ± SD of one representative experiment performed in triplicate. *Statistical difference as assessed by statistical analysis (P < .05).