Age and sex differences in immune response following LPS treatment in mice

Puberty is an important developmental event that is marked by the reorganizing and remodeling of the brain. Exposure to stress during this critical period of development can have enduring effects on both reproductive and non-reproductive behaviors. The purpose of this study was to investigate age and sex differences in immune response by examining sickness behavior, body temperature changes, and serum cytokine levels following an immune challenge. The effects of circulating gonadal hormones on age and sex differences in immune response were also examined. Results showed that male mice display more sickness behavior and greater fluctuations in body temperature following LPS treatment than female mice. Moreover, adult male mice display more sickness behavior and a greater drop in body temperature following LPS treatment compared to pubertal male mice. Following gonadectomy, pubertal and adult males displayed steeper and prolonged drops in body temperature compared to sham-operated counterparts. Gonadectomy did not eliminate sex differences in LPS-induced body temperature changes, suggesting that additional factors contribute to the observed differences. LPS treatment increased cytokine levels in all mice. However, the increase in pro-inflammatory cytokines was higher in adult compared to pubertal mice, while the increase in anti-inflammatory cytokines was greater in pubertal than in adult mice. Our findings contribute to a better understanding of age and sex differences in acute immune response following LPS treatment and possible mechanisms involved in the enduring alterations in behavior and brain function following pubertal exposure to LPS. (C) 2016 Elsevier Inc. All rights reserved.