a, Expression levels of the CBM-complex scaffold protein CARMA1 are associated with different levels of IFN-γ production in TREG cells following in vitro stimulation and in vivo tumour challenge. LN, lymph node. b, The genetic or pharmacological loss of CBM signalling results in the increased production of IFN-γ in tumour-associated TREG cells. IFN-γ production by TREG cells may affect MHC-I, MHC-II and PD-L1 on tumour cells and on antigen-presenting cells. ↑, increased expression; ?, unknown effects.