Parallel worlds of the adaptive and innate immune cell networks

Adaptive and innate immune cells have typically been functionally and temporally segregated even though they share a number of salient features. Over the past decade, significant advances have been made in understanding the composition and diversity of both innate and adaptive cell populations. This has shed light on how cells from two distinct pathways are so highly complementary. Innate lymphoid cells (ILCs) are pivotally positioned in tissues to form a stable population akin to tissue-resident T cells that protects the body. Nevertheless, the pathway by which different lymphocytes enter tissues, terminally differentiate and are replenished to maintain populations remains incompletely understood. Recent evidence challenges our assumptions about the sedentary lifestyles of so called 'tissue-resident cells' and pushes us to consider their roles in orchestrating protection of the immune system beyond the classical models.