Human gene expression changes with the seasons according to a paper published in Nature Communications. These changes, which display opposing patterns in the Northern and Southern hemispheres, appear to influence human health and could help to explain why certain infectious and chronic diseases display seasonal patterns.
It is well known that the expression of certain ‘circadian’ genes rises and falls with the 24 hour cycle and that these genes are also a major regulator of the mammalian immune response, but whether or not the seasons can influence gene expression is much less clear. By studying genetic data from a number of publicly available datasets, John Todd, Chris Wallace and colleagues now show that approximately a quarter of all genes show significant seasonal differences in expression and that the relative composition of various immune cells in the blood changes with the seasons too.
They find that in the European winter the pattern is pro-inflammatory, with increased levels of cardiovascular and autoimmune disease-linked proteins detected in the blood. People living in West Africa show a peak in seasonal cell types between June and October when the rains set in and malaria and other infectious diseases are more prevalent. The authors propose that their data changes the way in which human immunity should be conceptualised and suggest that it could be used to help time vaccination programs so they are delivered when they are most effective.