Daily patterns in the body's biochemical and physiological processes called circadian rhythms may influence immune-system function. Erol Fikrig and his colleagues at Yale University in New Haven, Connecticut, have found that the expression of an immune protein called TLR9 rises and falls with the circadian cycle.

They induced sepsis in mice to examine whether pathogen recognition — a key part of the immune response — varies with circadian cycles. Higher TLR9 expression at the time of sepsis induction was linked to a worse outcome for mice. This suggests that daily fluctuations in biological processes may influence vulnerability to infections, as well as the efficacy of immune therapies such as TLR9 agonists, which are currently in development.

Immunity http://dx.doi.org/10.1016/j.immuni.2011.12.017 (2012)