FIG. 8.

NK cells associate tightly with infected macrophages. Macrophages (2 × 10⁵) were infected with GFP-B. suis (MOI = 20) in eight-chamber culture slides and cultured in the presence of syngeneic NK cells (2 × 10⁵) in 400 μl of RPMI-FCS-gentamicin. At 24 h p.i., infection was assayed by consecutive visualization of the GFP-B. suis-infected cells by phase-contrast microscopy and UV fluorescent microscopy. The merged images of both observations showed a tight association between an infected macrophage (Mac.i.) and the NK cells, whereas noninfected macrophages (Mac.) poorly interact with NK cells.