Lymphocyte subpopulations and catecholamines; daytime variations and relationships

The diurnal variations and their possible relations with endogenous catecholamines have been studied in 16 apparently healthy subjects (8 women and 8 men, between 22-35 years of age). A butterfly cannula was inserted into the flexure vein of the elbow at 8 h and at 20 h, a blood sample being taken after three 15-minute intervals. Leukocytes, lymphocytes, monocytes, and granulocytes were quantified in a cell counter while lymphocyte subpopulations were determined with flow cytometry in cells labelled with specific monoclonal antibodies. Plasma catecholamine concentrations were measured by high-pressure liquid chromatography. Significant differences for leukocyte circulating levels were found, as well as for all subpopulations measured at different times of day, save NK cells and monocytes. A statistically significant correlation was also found both between leukocytes, all subpopulations and epinephrine save B lymphocytes and NK cells, and between total lymphocytes, T lymphocytes, CD4, CD4/45RA+ subtypes and norepinephrine. In conclusion, diurnal rhythms were proved to exist in leukocyte and lymphocyte subpopulations; the significant correlation between these cells and catecholamine plasma levels suggests the presence of a possible mechanism that connects the cellular immunity with determined hormones.