For instance, expression of apoptotic markers (i.e., Fas, FasL, Bax, Bcl-x, caspase 8, caspase 9, and caspase 3), when assessed by immunohistochemistry, are not present nor is there evidence of the DNA fragmentation marker TUNEL in the basal forebrain of individuals with AD (Wu et al., 2005). Here, CASP8 is linked to Alzheimer disease.