Seasonal changes in activities of human neutrophils in vitro.

Objective And Design: We present a retrospective analysis of previously collected blood samples to determine whether the immune response of neutrophils depends on the season i.e., short versus long days, in which blood samples were collected.

Methods: The bactericidal activity and adhesive capacity of neutrophils, the production of reactive oxygen species (ROS), and CD11b/CD18 molecule expression level were investigated. The investigated neutrophils were divided into two groups based on the time of blood collection: the winter season with short days and the summer season with long days.

Results: We found seasonal variation in measurements of all the analyzed functional responses of neutrophils to stimuli. The strongest adhesion, as well as maximum values of ROS production, was presented by neutrophils isolated from the summer group. The highest bactericidal activity of neutrophils was also observed in blood donors from summer group.

Conclusions: The magnitude of the immune functional activity of neutrophils varies with the season of the year and is decreased in winter.