Docent Lempainen’s thesis in 2009 focused on the pathogenesis of type 1 diabetes. Since then her research work has further focused on the heterogeneity of type 1 diabetes pathogenesis. In 2011 she worked as visiting researcher in the BabyDiab-diabetes study group in  Munich, Germany. Her current research interests comprise the etiology of beta-cell autoimmunity in respect of immunological, genetic and epigenetic factors and disturbances in early microbial contacts and are a part of the prospective Diabetes Prediction and Prevention (DIPP) study. In addition, she participates in research projects aiming at early detection of bacterial and viral infections in infants and children in order to avoid unnecessary antibiotic exposure. Since January 2020 docent Lempainen is the principal investigator of the Immunogenetics laboratory and PI and member of steering committee in the DIPP study at the University of Turku.