Differentiation of human innate lymphoid cells (ILCs)

• Murine ILCs develop from common ILC progenitor (CILP) which has not been identified in humans.
• Human ILCs develop from CD34+ precursors in vitro and in vivo.
• Human NKp is present in bone marrow, cord blood, and tonsils.
• Human ILC3p is present in tonsils and intestine but not in bone marrow.

During the last years, a high complexity in innate lymphoid lineages now collectively referred to as innate lymphoid cells (ILCs) has been revealed. ILCs can be grouped according to their effector functions and transcriptional requirements into three main groups, termed group 1, 2 and 3 ILCs. The differentiation of ILC lineages from hematopoietic precursors and the molecular switches guiding their developmental fate have started to be characterized both in mice and humans. In this review, we discuss the origin, differentiation stages and plasticity of human ILC subsets as well as the signals that drive ILC lineage commitment and acquisition of their unique effector programs.