FIG. 6.
Induction of tolerance and cross-tolerance in primary bone marrow cells from TLR2+/+ and TLR2−/− mice. Bone marrow cells (5 × 105/well) from TLR2+/+ mice (black bars) and TLR2−/− mice (striped bars) were incubated with culture medium (con), 1 and 10 ng of LPS/ml, or 105, 3 × 105, or 106 heat-inactivated Borrelia cells (heat-inact. Bb) for 24 h and then washed and incubated for another 24 h in the presence of 1 ng of LPS/ml (a and b) or 10 μg of Borrelia lysate/ml (c and d). The concentrations of TNF-α were measured by ELISA. Data are expressed as the means ± SEM divided by the viability assessed by the MTT assay. The statistical significance is for comparison with the nontolerized cells. * represents a P value of <0.05 and *** represents a P value of <0.001 based on ANOVA followed by Dunnett's multiple comparison test. n.d., not detectable.