Mammalian mothers set their offspring up for life by feeding them milk. But breast milk is more than a source of nutrients; according to a new study, it also gives mothers a way of preparing their young for challenges ahead. Researchers from Weill Cornell Medical College found that if female mice lack a protein called TNF, they produce breast milk with low levels of cytokines — chemicals involved in triggering an immune response. If pups drink this cytokine-poor milk, they develop a bigger hippocampus — a part of the brain involved in spatial memory. UTMB’s Dr. Roberto Garofalo noted that human milk contains TNF along with several other chemokines. “But there is some evidence that this TNF may be biologically inactive because milk contains soluble TNF receptors that inactivate it,” he added. “The endpoint in humans would be a sort of TNF inhibition, similar to what they obtain in genetically-deficient mice or with pharmacologic inhibitors.”