Toll-like receptor responses in tuatara

Toll-like receptors (TLR) are an evolutionarily-conserved family of pattern recognition receptors that are a key component of innate immune responses. To understand if leukocytes from tuatara (Sphenodon punctatus), an evolutionarily distinct reptile species, expressed TLR, we isolated blood leukocytes from tuatara and analysed their ability to respond to known TLR2, TLR3, TLR4, and TLR7/8 agonists. We found that all tuatara could respond to these agonists but that responses were significantly greater in leukocytes isolated in summer compared to winter. Additionally, these impaired innate responses correlated with a reduction in monocytes during winter. The finding that tuatara have impaired innate responses during winter has important implications for conservation and in particular, for the relocation of animals.