In addition, it has been found that cystatin C and Aβ colocalize in the amyloid deposition of brain parenchyma and cerebral vessels of AD patients (Sastre et al., 2004), and this study also found colocalization of cystatin C and APP in transfected cells and cell membranes through immunofluorescence analysis and a combination of cystatin C, full-length APP and secreted βAPP through western blots of immunoprecipitated cell lysates and culture proteins (Finckh et al., 2000). Here, APP is linked to Alzheimer disease.