Type 2 innate lymphoid cells: friends or foes-role in airway allergic inflammation and asthma

Association between group 2 innate lymphoid cells enrichment, nasal polyps and allergy in chronic rhinosinusitis

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) were shown to be involved in the initiation and coordination of Th2-type immune responses in allergic disease animal models. Recently, ILC2s enrichment was noted in chronic rhinosinusitis (CRS) patients; however, the role of ILC2s in coordinating the Th2 response in CRS remains to be elucidated. Here, we characterize the ILC2 compartment in CRS by investigating the correlations between ILC2s, Th2 cells and Th2 cytokines expression in CRS patients.

METHODS

We used flow cytometric analysis of sinonasal mucosal tissues of 29 CRS patients and 5 controls to quantify ILC2s and Th2 cells. Messenger RNA expression levels of IL-5, IL-13, IL-25, IL-33, TSLP and GATA3 were determined using qRT-PCR.

RESULTS

ILC2s were significantly enriched in nasal polyps (CRSwNP) patients. Multivariate linear regression showed a significant positive association of ILC2 numbers with CRSwNP and allergic CRS and a negative association with the number of previous endoscopic sinus surgeries. Group 2 innate lymphoid cell numbers significantly correlated with Th2 cell frequencies. Messenger RNA expression levels of IL-5 and IL-13 were increased in CRSwNP compared with controls, while mRNA levels of IL-25 and GATA3 were significantly reduced.

CONCLUSIONS

Our results characterize the complex interactions between ILC2s and other Th2 response elements in the context of CRS and suggest that ILC2 enrichment occurs in CRSwNP and in allergic CRS patients.

TNF superfamily member TL1A elicits type 2 innate lymphoid cells at mucosal barriers

Immune responses at mucosal barriers are regulated by innate type 2 lymphoid cells (ILC2s) that elaborate effector cytokines interleukins 5 and 13 (IL5 and IL13). IL25 and IL33 are key cytokines that support ILC2s; however, mice deficient in these pathways retain some functional ILC2s. Analysis of human and murine cells revealed that ILC2s highly express tumor necrosis factor (TNF)-receptor superfamily member DR3 (TNFRSF25). Engagement of DR3 with cognate ligand TL1A promoted ILC2 expansion, survival, and function. Exogenous protein or genetic overexpression of TL1A activated ILC2s independent of IL25 or IL33. Dr3(-/-) mice failed to control gut helminthic infections, and failed to mount ILC2 responses in the lung after nasal challenge with papain. Our data demonstrate a key role for TL1A in promoting ILC2s at mucosal barriers.