The maternal interleukin-17a pathway in mice promotes autism-like phenotypes in offspring

A T cell cause for autism? The causes of autism spectrum disorder (ASD) are complex and not entirely clear. Alterations in the mother's immune system during pregnancy, especially during key early periods of fetal neurodevelopment, may play a role. Choi et al. provided infectious or inflammatory stimuli to pregnant mice, which resulted in of spring exhibiting behaviors reminiscent of ASD (see the Perspective by Estes and McAllister). A subset of T helper cells that make the cytokine interleukin-17a in the mothers caused cortical defects and associated ASD behaviors in offspring. Therapeutic targeting of interleukin-17a during gestation reduced ASD symptoms in offspring. Science, this issue p. 933; see also p. 919 Interleukin-17–producing T cells act during gestation to induce cortical and behavioral abnormalities in offspring. [Also see Perspective by Estes and McAllister] Viral infection during pregnancy has been correlated with increased frequency of autism spectrum disorder (ASD) in offspring. This observation has been modeled in rodents subjected to maternal immune activation (MIA). The immune cell populations critical in the MIA model have not been identified. Using both genetic mutants and blocking antibodies in mice, we show that retinoic acid receptor–related orphan nuclear receptor gamma t (RORγt)–dependent effector T lymphocytes [for example, T helper 17 (TH17) cells] and the effector cytokine interleukin-17a (IL-17a) are required in mothers for MIA-induced behavioral abnormalities in offspring. We find that MIA induces an abnormal cortical phenotype, which is also dependent on maternal IL-17a, in the fetal brain. Our data suggest that therapeutic targeting of TH17 cells in susceptible pregnant mothers may reduce the likelihood of bearing children with inflammation-induced ASD-like phenotypes.