APP and Alzheimer disease: In summary, based on our screened antibody pairs 1F12/2C6 and 1F12/1F12 in sandwich ELISA for specific detection of Aβ42Ms and Aβ42Os, we observed apparent fluctuation in the levels of Aβ42Ms and Aβ42Os in blood and intestines of APP/PS1 mice during the progression of AD.