FIG. 5.

The impairment of B. suis intramacrophagic development requires cell-to-cell contact between infected macrophages and NK cells. B. suis-infected macrophages (8 × 10⁵/ml) were kept in cultures with syngeneic NK cells (8 × 10⁵/ml) in the absence (○, ▾) or presence (▿, ▪) of rIL-2 (100 U/ml) (conditions of Fig. 2). NK cells and macrophages were either in direct contact (○, ▿) or separated by a semipermeable membrane (▾, ▪), where the NK cells were on the upper part of the membrane. The control represented the development of B. suis in infected macrophages cultured without any NK cells (•). At different times p.i., the intramacrophagic number of viable Brucella was measured and expressed in CFU/well. Results are means ± SEMs (error bars) of four different experiments.