FIG. 1.

The intramacrophagic development of B. suis is reduced in the presence of syngeneic NK cells. A total of 8 × 10⁵ human macrophages were infected with B. suis in 24-well plates as described in Materials and Methods. After extensive washing, different amounts of syngeneic NK cells were added (or not) to the infected cells. Both cell populations were cocultured in 1 ml of culture medium (RPMI-10% FCS) supplemented with gentamicin. The ratio of the number of NK cells to the number of B. suis-infected cells varied from 0.1 to 2. After 48 h of incubation, the number of intramacrophagic viable B. suis cells was determined and expressed as CFU per well. For each experimental condition, experiments were performed in triplicate. Values are the means + SEMs (error bars) of four similar experiments performed separately.