Brief maternal separations of neonatal animals can exert long-lasting effects on the reactivity of the neuroendocrine system. The aim of the present study was to investigate whether manipulations of the mother-infant interaction could affect susceptibility to immune-mediated diseases, such experimental autoimmune encephalomyelitis (EAE), and whether this effect would be mediated by changes in leptin which has been shown to regulate disease susceptibility and severity at adulthood. Given the different gender susceptibility to EAE previously described, we tested also whether early experiences could differentially affect the two genders. To this purpose, female and male C56BL/6 mice were subjected to handling (15 min daily) postnatally, from day 2 until day 14. All subjects were weaned at 21 days. At 7 weeks of age mice were immunized with MOG(35-55) to actively induce EAE. We thus determined the effect of neonatal handling on plasma concentrations of testosterone in male mice and leptin in both genders at different times post EAE induction. Our results show that early experiences influence susceptibility to EAE in a gender-specific manner, early manipulations resulting in an enhancement of sex-related differences in susceptibility. These effects were associated with changes in the testosterone profile of male subjects. Changes in leptin levels during the preclinical stage of EAE may predict a more severe disease course.