The effects of diurnal rhythms on immune parameters in New Hampshire chickens

The influence of diurnal rhythms on several immune parameters was studied. When thymic-derived lymphocytes were collected 4 times during a 24-hour period, a variation occurred in the migration ability of these cells. The migration of T cells at 2:00 a.m. was markedly lower than at other time periods. Similar results were noted employing other T-cell tests: phytohemagglutinin wattle responsiveness and the graft vs. host assay.