 Early life immune activation can lead to sex-specific behavioral deficits and changes in the brain structure of adolescents. In particular, males are more likely than females to experience such deficits after exposure to a virus or other type of immune activation during their first few weeks of life. The virus causes inflammation in the brain, leading to increased levels of IFN, which then alters the function of microlia, resulting in decreased levels of excitatory synapses and increased levels of phagocytosis. This leads to long-term impairments in cognitive and social behaviors in males, but not females. This article was authored by Maria Schwabenland, Omar Mohsad, Anika Sivat, and others.