Results
The relative number of lymphocytes and neutrophils, as well as the relative number of neutrophils and monocytes, were negatively correlated, while the relative number of monocytes and eosinophils were positively correlated (Table S1).
Immune phenotype and variation with age
Over the course of an individual’s life, the number of lymphocytes decreased with age (quadratic delta age: β = 3.70.10-1, 95% CI = 0.26, 0.47; delta age: β = -5.55.10-1, 95% CI = -0.71, -0.39; Table 1; Figure 1B). On the reverse, the number of neutrophils (quadratic delta age: β = -0.25, 95% CI = -0.32, -0.18; delta age: β = 0.35, 95% CI = 0.25, 0.45; Table 1; Figure 1C) and eosinophils (quadratic delta age: β = -0.36, 95% CI = -0.711, -0.019; delta age: β = 0.262, 95% CI = -0.62, 0.67; Table 1; Figure 1E) increased while an individual ages.
The age at access to dominance did not affect both lymphocytes and neutrophils relative numbers (Table 2). However, among-individuals, the higher the age at last observation increased, the higher the number of lymphocytes (β = 0.27, 95% CI = 0.15, 0.40) and the lower the number of neutrophils (β = -0.15, 95% CI = -0.21, -0.08) were. This indicates no selective appearance but selective disappearance for individuals with low number of lymphocytes and high number of neutrophils.
The leukocyte concentration (Figure 1A) and the number of monocytes (Figure 1D) did not vary with age (both among- and within-individual, linear or quadratic effects were not significant, Table 1) and were not affected by age at access to dominance nor by age at last observation (Table 2).
We did not find any difference in the age-trajectories between males and females (non-significant interactions between ‘delta age’ and ‘sex’ removed from the final models). We also did not observed sex differences in the average leukocyte concentration and profiles, except that males had fewer lymphocytes than females (β = -0.22, 95% CI = -0.41, -0.04, Table 1).