Direct co-stimulation of cytotoxic T lymphocyte (CTL) lines via Toll-like receptor (TLR)-2. CD8+ T cells from CTL lines (generated against BALB/c, sixth stimulation, day 4) were cultivated on anti-hamster (ha)IgG plus anti-CD3 (0.3 or 0.03 ng per well) or anti-haIgG coated plates (control) in the presence or absence of Lip-OspA, Met-Asp-Pro (MDP)-OspA (10, 1 or 0.1 μg/ml each), recombinant interleukin-2 (rec. IL-2; 50 U/ml), concanavalin A (ConA; 5 μg/ml) or lipopolysaccharide (LPS; 1 μg/ml) for 48 h. Proliferation of cells was measured by [3H]thymidine incorporation. Means ± SEM for six different wells are given. Asterisk denotes significant difference (P < 0.05) from control (anti-haIgG or anti-CD3 without supplements). One representative experiment is shown. Phenotypic analysis (fluorescence-activated cell sorting) of C57BL/6 (B6), TLR-2-/- and TLR-4def anti-BALB/c CTL lines (third stimulation, day 4): Thy1.2+, 99.0–99.5%; CD8+, 93–95%, CD4+, 0.7–2%; CD19+ (B cells), F4/80+ (macrophages), NK1.1+ (NK cells) ≤ 0.2%. SI, stimulation index (calculated based on results with anti-haIgG plus anti-CD3 or with anti-haIgG alone, without the addition of supplements).