The immune system constitutes a sensory system both for heritable and non-heritable factors. Among the latter, social and environmental determinants of health may influence and shape the immune system in early life. To study the relationship between leukocytes and determinants of health in adolescence, we assessed total and differential white blood cells (WBC) according to social and environmental determinants of health in a healthy adolescent population.

As part of the population-based cohort Epidemiological Health Investigation of Teenagers in Porto (EPITeen), 1213 adolescents were evaluated at the age of 13. Total and differential WBC were evaluated through a venous blood sample using an automated blood counter (Sysmex®XE-5000, Hyogo, Japan). Sociodemographic, behavioral, and clinical data were collected through self-administered questionnaires.

Participants with better socioeconomic conditions (enrolled at private schools or higher parental education) had significantly lower total WBC levels, and the latter showed a lower percentage of neutrophils and higher percentage of lymphocytes. Those who practiced sports had significantly lower total WBC levels and neutrophil percentage, as well as a significantly higher percentage of eosinophils and lymphocytes. Adolescents with chronic disease, chronic medication, or allergic diseases had a significantly higher percentage of eosinophils and a lower percentage of monocytes. With increasing body mass index and systemic inflammation, we found a significant increase in total WBC levels.

WBC linked to different immune response patterns are associated with several social and environmental determinants of health in adolescence.