Exercise and Human Immunity in Adolescents (12–18 Years): Biomarkers, Sex Differences, and Evidence From Mexico and International Studies: a Narrative Review

Resumen

Purpose: To synthesize mechanistic and clinical evidence linking exercise to immune modulation, highlight key laboratory and clinical indicators, and summarize adolescent (12– 18 years) data including sex differences and evidence from Mexico versus international studies. Methods: Narrative review focusing on meta-analyses/systematic reviews and primary studies reporting immune biomarkers (leukocyte subsets, salivary IgA, immunoglobulins, cytokines/interleukins) in relation to exercise intensity and volume in youth. Results: Consistent evidence indicates that regular moderate exercise improves immune surveillance and anti-inflammatory balance, reflected by transient mobilization of NK cells and T cells, higher salivary IgA, and lower chronic inflammatory markers (eg, CRP, TNF-α) in trained versus sedentary youth (1–5,8–12). Excessive load with inadequate recovery is associated with short-term susceptibility signals (eg, reduced salivary IgA) and higher illness burden in some athlete cohorts (3,9,15,26). Sex differences during adolescence may include stronger humoral responses in females and greater cytotoxic-cell mobilization in males, partly mediated by pubertal hormones (18–20). Evidence from Mexico remains limited but aligns with international patterns, particularly where obesity/inflammation and activity levels are assessed (28–30). Conclusions: Exercise is a potent, dose-dependent immunomodulator in adolescents. Periodized training with adequate recovery optimizes immune outcomes; screening for acute illness, energy deficiency, and overreaching is essential in youth sport.