KIT and Alzheimer disease: To investigate the role of mast cells (MCs) and MC-specific proteases on the immunopathogenesis of AD, a vitamin D3-analog (MC903) was used to induce clinical AD-like symptoms in c-kit-dependent MC-deficient Wsh−/− and the MC protease-deficient mMCP-4−/−, mMCP-6−/−, and CPA3−/− mouse strains.