Innate lymphoid cells: More than just immune cells

Abstract

Since their discovery, innate lymphoid cells (ILCs) have been described as the innate counterpart of the T cells. Indeed, ILCs and T cells share many features including their common progenitors, transcriptional regulation, and effector cytokine secretion. Several studies have shown complementary and redundant roles for ILCs and T cells, leaving open questions regarding why these cells would have been evolutionarily conserved. It has become apparent in the last decade that ILCs, and rare immune cells more generally, that reside in non-lymphoid tissue have non-canonical functions for immune cells that contribute to tissue homeostasis and function. Viewed through this lens, ILCs would not be just the innate counterpart of T cells, but instead act as a link between sensory cells that monitor any changes in the environment that are not necessarily pathogenic and instruct effector cells that act to maintain body homeostasis. As these non-canonical functions of immune cells are operating in absence of pathogenic signals, it opens great avenues of research for immunologists that they now need to identify the physiological cues that regulate these cells and how the process confers a finer level of control and a greater flexibility that enables the organism to adapt to changing environmental conditions. In the review, we highlight how ILCs participate in the physiologic function of the tissue in which they reside and how physiological cues, in particular neural inputs control their homeostatic activity.

Deciphering decidual leukocyte traffic with serial intravascular staining

“…Similarly, innate lymphoid cells (ILCs) have been identified in both the murine ( 11 , 25 , 26 ) and human decidua ( 8 , 27 , 28 ) and have been associated with pre-term birth ( 29 , 30 ). Although ILCs are found in circulation, they are most abundant at mucosal sites ( 31 , 32 ). And, like NK cells, many novel subsets have been identified in the decidua ( 33 , 34 ), however, questions remain as to whether they are recruited from the circulation or whether they proliferate and differentiate in situ.…”

Analysis of influencing factors of serum SCCA elevation in 309 CAP patients with normal CEA,NSE and CYFRA21-1

“…The study also found that TRPM8 expressed in dermis was partially responsible for the activation of skin-resident ILC2s,and TRPM8,which is expressed in epidermal keratinocytes, may also be involved in sensing ambient temperature to promote local ILC2s activation ( 31 ). ILC2s express the transcription factors GATA 3 and RORα during development which are capable of producing type 2 cytokines such as IL-4,IL-5,and IL-13 ( 31 , 34 ). Stimulated by interleukin-4 (IL-4) or interleukin-13 (IL-13), keratinocytes can secrete SCCA1 and SCCA2 ( 17 , 21 ).…”

Both Horatio and Polonius: Innate Lymphoid Cells in Tissue Homeostasis and Repair

“…For one, they can develop in the absence of the RAGs, RAG1 and RAG2, and express either nonrearranged or minimally rearranged transcripts for TCR chains, suggesting a potential shared origin from IL7R + lymphoid primed multipotent progenitors that fail to undergo or attempt abortive thymic T-cell selection ( 16 ). In contrast to myeloid cells, ILCs rarely rely on pattern recognition through the TLR and NOD-like receptor families ( 25 , 26 ), instead sensing tissue perturbation through both “canonical” cytokine signals and a bevy of noncanonical (nonpeptide) signals such as neurotransmitters, lipids, dietary metabolites, and other small molecules ( 2 , 3 ). An overview of this array of sensed ILC environmental inputs is provided in Fig.…”

“…However, there is now increasing appreciation for homeostatic functions for ILCs in maintaining tissue integrity and shaping host responses well after acute perturbation ( 3 ). Thus, ILCs have a balanced, advisory role as a homeostatic “Horatio”: integrating diverse environmental cues to engage appropriate repair pathways and mitigate excessive tissue injury.…”