IL-33 supports T_H1 cells

The alarmin interleukin-33 (IL-33) is most typically associated with the initiation and enhancement of type II and T helper 2 (T_H2) responses. In the Proceedings of the National Academy of Sciences, Löhning and colleagues find that IL-33 can also drive T_H1 effector function. T_H1 cells generated in a lymphocytic choriomeningitis virus (LCMV) model express a functional IL-33 receptor (ST2), albeit transiently and at lower amounts than that seen on T_H2 cells. Expression of ST2 by T_H1 cells is dependent on expression of the transcription factors STAT4 and T-bet. ST2 is not required for T_H1 differentiation or homeostatic maintenance, but its absence impairs their effector function upon LCMV infection. Accordingly, LCMV-specific T_H1 cells deficient in ST2 mediate less immunopathology after infection. Therefore, in addition to its well-established roles driving type II responses, IL-33 also seems in some other contexts to drive T_H1 cells functions.

Proc. Natl. Acad. Sci. USA (17 March 2015) doi:10.1073/pnas.1418549112