The circadian clock influences response to vaccines, with immune cells behaving differently depending on the time of day, according to a new analysis.
The immune cells called dendritic cells play a critical role in the adaptive immune response after infection or vaccination.
These cells and others in the immune system display "circadian rhythmicity in gene expression", say researchers from the Royal College of Surgeons in Ireland University of Medicine and Health Sciences, Dublin, Ireland, in Monday’s *Nature Communications*.
They produce daily oscillations in a range of critical immune cell functions, the researchers add, including antiviral immune responses.
For example, it has previously been found in elderly people, that flu vaccinations given in the morning generate higher antibody levels.
The researchers investigated the mechanisms behind these time-of-day differences, focusing on dendritic cells.
They carried out lab tests on mice and found greater T cell responses when the animals were immunised during their rest phase compared with their active phase.
"We find a circadian rhythm in antigen processing that correlates with rhythms in both mitochondrial morphology and metabolism, dependent on the molecular clock gene, Bmal1," they report.
They went on to test the impact of a compound that "promotes mitochondrial fusion", called Mdivi-1.
Using this, they were able to "rescue the circadian deficit in antigen processing and mechanistically link mitochondrial morphology and antigen processing".
They also found that circadian changes in calcium levels in the mitochondria are important to the processing of antigens.
Co-author Professor Annie Curtis said: “Our discovery has shed light on a crucial aspect of our body’s response to vaccination and highlights the importance of circadian rhythms in immunity.
"We can apply this understanding in vaccine development to ensure we receive the maximum benefits from vaccination.”
Cervantes-Silva, M.P. et al. The circadian clock influences T cell responses to vaccination by regulating dendritic cell antigen processing. *Nature Communications* 5 December 2022; doi: 10.1038/s41467-022-34897-z
Leave a Reply