Reference intervals for leukocyte subsets in adults: Results from a population-based study using 10-color flow cytometry.

BACKGROUND: Reference intervals for leukocyte subsets from peripheral blood are helpful for the understanding of disease states and therapy effects. METHODS: We performed in-depth immunophenotyping for 608 healthy German adults from the Leipzig region from 40 to 79 years by 10-color flow cytometry (FCM) to gain reference information for various leukocyte subsets including subsets of granulocytes, monocytes and lymphocytes. RESULTS: First, we derived gender- and age-specific reference intervals for males and females from 40 to 59 and from 60 to 79 years, respectively. Second, we further investigated the influence of gender and age on leukocyte counts. We found significantly higher cell counts for monocytes (P < 0.001) and NK cells (P < 0.001) in men, whereas women had higher counts for B cells (P < 0.001), Th cells (P < 0.001) and regulatory T cells (P = 0.008). Furthermore, with increasing age, a decrease in Tc cells (about 8% within 5 years) and an increase in NK cells (<4% within 5 years) were observed. CONCLUSION: In future research, it should be investigated whether these are real ageing effects that can be confirmed in longitudinal studies. Furthermore, it is important to understand if the Tc cell count drop is functionally compensated by the increase of NK cells.