Improvements in Behavior and Immune Function and Increased Life Span of Old Mice Cohabiting With Adult Animals

The social environment can affect the regulatory systems, and cohabitation with sick subjects is a negative factor for the nervous and immune systems, compromising the life span. Nevertheless, the possible beneficial effects of a positive social environment on nervous and immune functions and longevity have not yet been studied. The aim of this study was to analyze several behavioral and immune function parameters and life span in old mice after their cohabitation with adult animals. Old and adult ICR-CD1 female mice were divided into three experimental groups: adult controls, old controls, and a social environment experimental group. The latter contained two old mice with five adult mice. After 2 months in these conditions, mice were submitted to a behavioral battery of tests to analyze their sensorimotor abilities, anxiety-like behaviors, and exploratory capacities. Peritoneal leukocytes were then collected, and several immune functions as well as oxidative and inflammatory stress parameters were assessed. The animals were maintained in the same conditions until natural death occurred. The results showed that old animals, after cohabitation with adult mice, presented an improvement of behavioral capacities, immune functions, and a lower oxidative and inflammatory stress. Consequently, they exhibited a higher life span.