Abstract
Effective immunoprotection requires rapid recruitment of leukocytes into sites of surgery, wounding, infection, or vaccination. Immune cells or leukocytes circulate continuously on surveillance pathways taking them from the blood into various organs and back into the blood. This circulation is essential for the maintenance of an effective immune defense network. The numbers and proportions of leukocytes in the blood provide an important representation of the state of distribution of leukocytes in the body and the state of activation of the immune system. Numerous studies have shown that stress and stress hormones induce significant changes in absolute numbers and relative proportions of leukocytes in the blood.