To derive dendritic cells from PBMCs and monocytes we cultured 1610 6 or 2610 5 cells/well, respectively, in 24-well tissue culture plates for 5 days in 2 ml of complete RPMI 1640 supplemented with 10 ng/ml IL-4, and 100 ng/ml recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) (R&D system, Minneapolis, MN). Cultures were placed at 37uC in a 5% CO 2 humidified incubator. Every two days the medium was removed and 2 ml of fresh complete medium was added. At day 5 the cells were co-cultured with 2.5 mg/ml of purified recombinant OspA or UV-killed recombinant Lactobacillus at MOI 10:1 colony-forming units per cell for 48 h at 37uC. 100 ng/ml of lipopolysaccharide (LPS) from Escherichia coli O111:B4 (LIST Biological Laboratories, Campbell, CA) and L. plantarum were used as positive and negative control, respectively. Supernatants were collected and TNFa, IL-12, IFNc, IL-6, and IL-10 were quantified by ELISA (Quantikine, R&D Systems).