FIG 1.

B. abortus invades and multiplies in murine osteocytes cells, inducing MMP-9 and cytokine secretion. (A) Osteocytes (MLO-Y4 cell line) and monocytes (J774.A1 cell line) were infected with B. abortus at an MOI of 100, and replication in each cell type was assessed by determining CFU counts after 2, 4, 24, 48, and 72 h. (B) MLO-Y4 cells were infected with B. abortus at different MOIs, and 24 h after infection MMP-9 production was determined by zymography. (C to F) Levels of RANKL, the cytokines TNF-α and IL-6, and KC, as indicated, were evaluated by ELISA in culture supernatants harvested at 24 h (RANKL, IL-6, and KC) or 8 h (TNF-α) postinfection. PMA, phorbol myristate acetate. Data are given as the means ± SD from at least three individual experiments. *, P < 0.1; **, P < 0.01; ***, P < 0.001, for results versus noninfected (NI) cells.