Lymphocyte subpopulations in healthy Ukrainian men: local reference ranges, long temporal stability, and...

Reliable interpretation of lymphocyte immunophenotyping depends on population-specific reference ranges that account for demographic and environmental factors. However, such reference data are currently lacking for the Ukrainian population. This study aimed to establish local reference ranges for lymphocyte subpopulations in healthy adult men and to assess their temporal stability and variability following physical exercise. Peripheral blood samples from 100 clinically healthy men aged 22-55 years were analyzed by flow cytometry to quantify T lymphocytes (CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺), B lymphocytes (CD3^-CD19⁺), and NK cells (CD3^-CD56⁺, CD3^-CD56⁺NKp46⁺). Temporal stability was evaluated in 24 participants monitored during a one-year Antarctic expedition, while acute immune responses were assessed in 19 men before and after a modified Cooper test. The established reference ranges were as follows: CD3⁺ (54.0-82.2%), CD3⁺CD4⁺ (29.3-54.0%), CD3⁺CD8⁺ (11.2-39.6%), CD3^-CD19⁺ (3.7-20.1%), CD3^-CD56⁺ (4.2-30.0%), and CD3^-CD56⁺NKp46⁺ (2.7-24.3%). Comparison with published studies revealed differences in several parameters, whereas discrepancies relative to reference values used by local laboratories were observed across multiple measures. Following a one-year Antarctic expedition, lymphocyte subset distributions remained largely stable despite a significant expansion of monocytes, whereas short-term physical exercise elicited pronounced, subset-selective increases in NK cells and monocytes, accompanied by concurrent elevations in cortisol and testosterone levels. The differences observed across populations and laboratories underscore the need for harmonized, population-based reference intervals.