TNF and infection: Furthermore, no cleavage of caspase-3 could be detected in western blots of lysates of IFNγ-induced, T. gondii-infected cells up to 8 hours after infection, nor cleavage of the caspase-3 substrate PARP, both of which signs of apoptosis [26] were easily detected in MEFs treated with cycloheximide and TNFα [25] (Fig. 5C).