Direct co-stimulation of cytotoxic T lymphocyte (CTL) lines by Lip-OspA can be inhibited by anti-Toll-like receptor (TLR)-2 monoclonal antibody. CD8+ T cells from C57BL/6 (B6) CTL lines (generated against BALB/c, fifth stimulation, day 4) were cultivated on anti-hamster IgG plus anti-CD3 (0.3 or 0.03 ng per well) in the presence or absence of Lip-OspA (10 μg/ml) with or without varying concentrations of anti-TLR-2 monoclonal antibody (25, 2.5 or 0.25 μg/ml) or the respective isotype control antibody (25 μg/ml) for 24 hours. Proliferation of cells was measured by [3H]thymidine incorporation. Means ± SEM for three to six different wells are given. Asterisk denotes significant difference (P < 0.05) from control (plus Lip-OspA without the addition of anti-TLR-2 monoclonal antibody). One representative experiment (out of two with similar results) is shown. SI, stimulation index (calculated based on results with anti-CD3 without the addition of supplements; white bars).