Rahul studied Natural Sciences at the University of Cambridge and Clinical Medicine at King’s College London. After completing Clinical Academic Foundation Training in London, Rahul undertook a Ph.D. in Dr Gary Nabel’s laboratory at the US National Institutes of Health (NIH) and a postdoctoral fellowship at Dr Nicholas Restifo’s laboratory at the US National Cancer Institute (NCI). Rahul has made important contributions to our understanding of immune regulation and lymphocyte gene regulation. A major contribution of his early research was the discovery of mechanisms underlying differentiation of a powerfully suppressive subset of T cells called regulatory T (Treg) cells. He discovered the critical function of the transcription factor BACH2 in Treg lineage specification (Roychoudhuri et al., Nature 2013; Vahedi et al., Nature 2015), and in suppression of immune responses against solid tumours (Roychoudhuri et al., J Clin Invest 2016). This work led to discovery of a new monogenic disease caused by BACH2 insufficiency (Nat Immunol 2017; reviewed in Nat Rev Immunol 2017). The laboratory's work has also shown that Treg differentiation in peripheral tissues is sensitive to local oxygen concentrations resulting in permissivity of the lung to cancer metastasis (Clever, Roychoudhuri, et al., Cell 2016).