Besides Th17 lymphocytes, other cellular sources of IL-17 include γδ T cells, cytotoxic T cells, invariant NK T cells, NK cells, and type 3 innate lymphoid cells (ILC3s) [12, 69]; the latter, which require RORγt and GATA3 transcription factors for their development, can be detected in the bronchoalveolar lavage fluid from patients with severe asthma [12, 70]. The gene discussed is IL17A; the disease is asthma.