FIG. 3.

DNA fragmentation assays. (A) DNA was isolated from J774 macrophages or PMNs and migrated on a 1.5% agarose gel. Lanes: 1, ladder molecular size markers; 2, uninfected J774; 3, CHA-infected J774; 4, CHA-D1-infected J774; 5, J774 treated by UV irradiation for 15 min; 6, uninfected PMNs; 7, CHA-infected PMNs; 8, CHA-D1-infected PMNs; 9, PMNs treated with 50 μM actinomycin D for 5 h. (B) Nuclear morphology of PMNs. At 2 h after infection with the CHA strain, cells were stained with the DNA-specific fluorochrome Hoechst 33342. Uninfected cells showed polymorphic nuclei typical for normal PMNs isolated from blood samples. CHA cells exhibited rounded, uniformly stained, swollen nuclei. Apoptotic cells (UV treated) showed typical highly condensed and fragmented nuclei. Observations were done using epifluorescence microscopy (magnification, ×1,000).