MASP2 and Calcium oxalate nephrolithiasis: MAp19 has also been suggested to act as an inhibitor of calcium oxalate kidney stone formation in human urine22, and a recent study showed an association between baseline serum MAp19 concentration and the incidence of microalbuminuria in a study cohort of 270 persons with newly diagnosed type 1 diabetes in an 18-year follow up study23.