Circadian rhythm in T, B and natural killer cells

Plaque-forming cell responses to sheep red blood cells show a striking 24-hr periodicity. This phenomenon is concordant with mounting evidence immunological responses are controlled by factors governing other circadian aspects of physiologic function. Proliferative responses of lymphocytes in both mice and man to the phytomitogen PHA also show circadian variability; the maximum responses to PHA in mice differ in circadian stage from the time when maximum responses to antigens are encountered. Natural killer-cell functions of mice, rats and man show clear evidence of circadian periodicity which may relate to a circadian resistance to cancer cell metastases and circadian variability of responses to cancer therapy.