APP and Alzheimer disease: Splice variants of amyloid precursor protein (APP) including APP751 and APP770 contain the Kunitz-type protease inhibitor (KPI) domain which blocks enzymatic degradation by serine proteases and may contribute to the pathological deposition of Aβ in the setting of AD; rats given a fluid-percussion TBI have increased APP751/770 levels 24 h post-injury but decreased cortical levels of a variant that lacks the KPI domain (APP695) 1 h post-injury (Masumura et al., 2000).