The biological clock ticking within some immune cells can influence how well they respond to vaccination, a study in mice has found.

Cells have molecular clocks that dial gene activity up or down in a daily cycle. These clocks can affect immunity. Nathalie Labrecque at the Maisonneuve-Rosemont Hospital Research Centre in Montreal, Canada, and Nicolas Cermakian at the Douglas Mental Health University Institute, also in Montreal, and their colleagues investigated how the circadian clock affects the way that immune cells called CD8 T cells respond to vaccination.

The team found that vaccination stimulated the production of more CD8 T cells during the middle of the day than at other time points. Genes associated with the activation of these T cells were also expressed at higher levels at the middle of the day than at night. Mice that lacked the key clock gene Bmal1 within CD8 T cells did not show this rhythmic response.