Abstract
Understanding the origins and developmental trajectory of innate lymphoid cell (ILC) progenitors has been of substantial interest to the fields of ILC biology and immunology. While mature ILC are rare lymphocytes, ILC progenitors represent an even smaller fraction of cells, providing additional challenges in studying them. Moreover, though the approaches to studying these cells are conceptually straightforward, the technical nuances that underlie them can substantially affect the quality of the data. Herein, we provide a detailed protocol for assessing the frequency of ILC progenitors in the bone marrow, their phenotype, and their potential to develop into mature ILC. These methods make up the foundation of in vivo investigations into ILC development, and we hope these thorough protocols and associated notes facilitate additional, high-quality inquiries into this fascinating field.