To study the role of MCs and mast cell proteases in AD we induced an AD-like inflammation by topical application of the low-calcemic vitamin D3-analog MC903 on the ear lobes of c-kit dependent MC-deficient (Wsh−/−) mice [18], or in mice lacking the MC-specific chymase (mMCP-4−/−) [19], or the MC tryptase (mMCP-6−/−) [20], or the MC carboxypeptidase A3 (CPA3−/−) [21]. The gene discussed is CPA3; the disease is Alzheimer disease.