CYCLIC CHANGES IN THE CONCENTRATIONS OF PERIPHERAL-BLOOD IMMUNE CELLSDURING THE NORMAL MENSTRUAL-CYCLE

The optimal availability of immune cells in the peripheral blood strea ms of women may play a critical role in their response to disease and therapeutic interventions. This study was designed to examine concentr ations of circulating white blood cells (WBC) including lymphocyte sub sets, during the 24-hr daily and 28-day menstrual cycles. Venous blood (20 ml) from five healthy young women was obtained at 0, 6, 12, and 1 8 hr on the 6th and 22nd day of the normal menstrual cycle. Cortisol, progesterone (P4), estradiol (E2), total WBC, granulocyte, monocyte, a nd total lymphocyte levels were measured. Using fluorescent activated cell scanning, levels of T, B, Helper (H), Suppressor (S) and Natural Killer (NK) cells were also determined. Significant differences in the diurnal and Day 6 and 22 means were identified using analysis of vari ance and the Student's t test. Mean WBC counts differed significantly between individuals and ranged from 3.63 +/- 0.33 to 8.60 +/- 1.00 on Day 6 and 3.75 +/- 0.56 to 9.45 +/- 0.98 on Day 22 (P < 0.05). Fluctua tions in the concentrations of peripheral blood immune cells followed a similar pattern for the time points selected. They were lowest in th e morning at 6 hr and reached peak concentrations in the evening at 17 hr or at midnight at 24:00 hr. Total WBC and granulocyte levels were consistently highest in the evening at 18 hr while lymphocyte levels e ither peaked in the evening or at midnight. Between midnight and early morning, levels of WBC, lymphocytes, T, B, H, and S cells all decreas ed significantly (P < 0.01) and subsequently increased significantly, between 6 hr and noon or noon and 18 hr (P < 0.01). When compared ever y 12 hr, the levels of WBC, granulocytes, lymphocytes, T, B, H, and S cells showed a significant day time rise between 6 and 18 hr (P < 0.02 ). NK cells revealed no significant fluctuations for any of the diurna l time paint comparisons examined in this study. The WBC means for all subjects on Day 6 was 6.15 +/- 1.96 and on Day 22 was 6.39 +/- 2.14, evidence that the total number of white blood cells was not significan tly altered between the 2 days. However when comparing specific time p aints during the day for the follicular (Day 6) and luteal (Day 22) ph ases of the menstrual cycle, significant differences were found. Most striking were the monocyte patterns, which revealed a nadir at 12:00 n oon on Day 6 and a peak at the same time on Day 22, WBC, and granulocy te levels were significantly higher at 12:00 noon on Day 22 (P < 0.05) and NK cells significantly lower on Day 6 at 18 hr (P < 0.01). Thus, within this population of normal menstruating women, quantitative and qualitative differences in the circadian and circalunar levels of peri pheral blood immune cells do exist.