CASP3 and infection: TUNEL analysis performed on DCs derived from Casp3−/− and Casp3+/+ mice 6 hours after infection with L. pneumophila revealed that 57% of the infected Casp3+/+ DCs were TUNEL positive, whereas only 9.5% of Casp3−/− DCs infected with WT L. pneumophila were TUNEL positive (Figure 3A, left panel and 3B).