The transcription factor RelB restrains group 2 innate lymphoid cells and type 2 immune pathology in vivo

The exact relationships between group 2 innate lymphoid cells (ILC2s) and Th2 cells in type 2 pathology, as well as the mechanisms that restrain the responses of these cells, remain poorly defined. Here we examined the roles of ILC2s and Th2 cells in type 2 lung pathology in vivo using germline and conditional Relb -deficient mice. We found that mice with germline deletion of Relb ( Relb −/− ) spontaneously developed prominent type 2 pathology in the lung, which contrasted sharply with mice with T-cell-specific Relb deletion ( Relb f/f Cd4-Cre ), which were healthy with no observed autoimmune pathology. We also found that in contrast to wild-type B6 mice, Relb -deficient mice showed markedly expanded ILC2s but not ILC1s or ILC3s. Moreover, adoptive transfer of naive CD4 + T cells into Rag1 −/− Relb −/− hosts induced prominent type 2 lung pathology, which was inhibited by depletion of ILC2s. Mechanistically, we showed that Relb deletion led to enhanced expression of Bcl11b, a key transcription factor for ILC2s. We concluded that RelB plays a critical role in restraining ILC2s, primarily by suppressing Bcl11b activity, and consequently inhibits type 2 lung pathology in vivo.