Overview of Treg clinical trials documented in clinicaltrials.gov. 2A. Manual curation of all study entries involving Tregs, with further subdivision according to data accrual, related disease entity, and type of study (observational, Obs, versus therapeutic, Tx). 2B. Number of observational (Obs) and therapeutic (Tx) study entries initiated in each year. 2C. Percentage of clinical studies in each phase (1 to 3) according to disease category; total number of studies per category indicated in parentheses. 2D. Distribution of most-studied diseases/organ systems in each category. CR, colorectal.