FIG. 2.

Induction of Borrelia cross-tolerance to LTA or LPS in human PBMC. Human PBMC (10⁶/well) from four different donors were incubated with culture medium (con, black bars); 0.1, 1, or 10 μg of Borrelia lysate/ml (white bars); or 10⁵ or 10⁶ heat-inactivated Borrelia cells (heat-inact. Bb; striped bars) for 24 h and then washed and incubated for another 24 h in the presence of 10 μg of LTA/ml (a) or 10 ng of LPS/ml (b). The concentrations of TNF-α were measured by ELISA. Data are expressed as the means ± SEM divided by the OD assessed by the MTT test. The statistical significance is for comparison with the nontolerized (con) 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.