Effect of Th1 and Th2 cytokines on DNA fragmentation in monocyte cultures. Ultraviolet fluorescence microscopic analysis of monocytes (1 × 10⁵ cells/mL) cultured for 48 hours in poly–L-lysine coated plates in the presence of medium alone (A) or either IL-2 (200 IU/mL; B), IFN-γ (10,000 IU/mL; C), IL-12 (400 ng/mL; D), IL-4 (400 ng/mL; E), IL-10 (400 ng/mL; F ), or a mixture of IL-4 (400 ng/mL) and IL-10 (400 ng/mL; G). After the 2-day culture, in situ DNA fragmentation was assessed by the TUNEL method using FITC-dUTP (see Material and Methods section). Strand break DNA in apoptotic cells were visualized in green (original magnification × 250). These results are from one representative experiment out of three.