In recent years, he has contributed to the description of a new primary immunodeficiency syndrome caused by activated PI3Kδ mutations (APDS) and his group demonstrated that deletion of PI3Kδ in regulatory T cells unleashes a potent anti-tumour response. He has published more than 100 articles and reviews in leading journals and is an internationally-leading authority on the role of PI3Ks in immunity, infection and cancer.