Does immune challenge affect torpor duration?

Abstract

1. Hibernation may alter the relationship between pathogens and their hosts; low host temperatures can prevent pathogen replication. Therefore, manipulating the timing and duration of torpor bouts could allow animals to gain an advantage over pathogens. 2. Thirty‐two Turkish Hamsters (Mesocricetus brandti) were placed in short‐day, cold conditions. After 10 weeks, 20 animals were challenged with an antigen to simulate a pathogen infection. Ten of these animals were returned to the cold (‘cold‐challenged’). The other 10 animals were placed in warm conditions (‘warm‐challenged’). Twelve animals received saline injections and were returned to the cold (‘cold‐control’). Cold‐challenged animals spent significantly more time in torpor than did cold‐control animals. 3. After 6·5 weeks, all animals were housed in warm conditions and ceased torpor. Both cold‐challenged and warm‐challenged animals received a second injection of antigen. There was no correlation between time spent euthermic and level of secondary humoral response of cold‐challenged animals. The secondary humoral response of the cold‐challenged animals was significantly lower than that of warm‐challenged animals. 4. In this study immune status influenced torpor duration, and torpor caused immunosuppression. Hibernators may manipulate body temperature in order to combat pathogens while their own immune systems are suppressed.