Percentiles 10th, 25th, 50th, 75th and 90th are presented for circulating white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils and basophils in healthy European adolescents (12.5-17.5 years, n = 405, 48.9% boys), considering age, sex, puberty and body mass index (BMI). CD3(+) (mature T cells), CD4(+) (T helper), CD8(+) (T cytotoxic), CD16(+)56(+) (natural killer), CD19(+) (B cells), CD3(+)CD45RA(+), CD4(+)CD45RA(+), CD8(+)CD45RA(+) (naïve), CD3(+)CD45RO(+), CD4(+)CD45RO(+) and CD8(+)CD45RO(+) (memory) lymphocytes were also analysed by immunophenotyping. Girls presented higher WBC, neutrophil, CD3(+)CD45RO(+) and CD4(+)CD45RO(+) cell counts and CD3(+)/CD19(+) ratio, and lower CD3(+)CD45RA(+) and CD4(+)CD45RA(+) counts than boys. Age was associated with higher neutrophil counts and CD3(+)/CD19(+), and lower CD19(+) counts; in boys, with lower CD3(+)CD45RA(+), CD4(+)CD45RA(+) and CD8(+)CD45RA(+) counts as well; in girls, with higher WBC, CD3(+)CD45RO(+) and CD4(+)CD45RO(+) counts. Pubertal maturation in boys was associated with lower WBC and lymphocyte counts; in girls, with higher basophil, CD3(+)CD45RO(+) and CD4(+)CD45RO(+) values. BMI was associated with higher WBC counts; in boys, also with higher lymphocyte counts; in girls, with higher neutrophil, CD4(+), CD3(+)CD45RO(+) and CD4(+)CD45RO(+) counts.
Conclusion: Our study provides normative values for circulating immune cells in adolescents, highlighting the importance of considering sex, age, pubertal maturation and BMI when establishing reference ranges for WBC in paediatric populations.