Abstracts (complete list) - Wissenschaft Online

Thomas Bollinger, Monika Bajtus, Annalena Bollinger, Stojan Dimitrov, Werner Solbach
Circadian Rhythm of Regulatory T Cell distribution and
function
Vaccination is a powerful tool for the prevention of infectious diseases. Relatively little is
known about the impact of the time point of vaccination on the ensuing immune
response. Previous studies showed that vaccination in the afternoon compared to that
applied in the morning hours caused a highly significant approx. fourfold higher mean
antibody titer. No information is available on the underlying mechanisms. One
possibility could be modulation of anti-vaccine immune responses by regulatory T cells
(Treg). Thus, it seems reasonable that number and/or function of Treg might have a
circadian rhythm. We investigated 12 healthy young men for 24 hours and monitored
various parameters in the peripheral blood bi-hourly. We analysed the absolute
numbers of Tregs by FACS using CD4-FITC- and CD25-PE-antibodies . Cosinor analysis
revealed significant circadian rhythm in this population with highest levels during night
time (approximately 95 Treg/µl blood) and lowest levels in the day (approximately 55
Treg/µl blood) . In a second study we addressed the analysis of the functional circadian
rhythm of Treg by performing proliferation and suppression assays for the measurement
of the suppressive capacity of Treg at different time points during a 24 hour period. The
first data provide evidence for circadian rhythm of regulatory T cell function with the
lowest suppressive capacity of Treg at 7:00 am. At 3:00 pm for example we measured a
significant higher suppressive capacity (p