In the last five years, the introduction of cellular therapies has revolutionized the management of haematological cancers. The success of this approach has encouraged others to seek novel means to treat a variety of critical illness syndromes. In this talk, we will review the current state of cell-based immune modulation for ARDS and sepsis. We will address the classification and biology of investigational cell therapies, alongside a discussion of the challenges associated with scaling them for widespread clinical use.