Abstract:Objective To investigate the influencing factors for lymphocyte subsets in children 0 to 6 years of age.Methods Umbilical artery blood samples from 45 healthy full-term infants and venous blood samples from 79 healthychildren between 0 and 6 years were collected. According to the methods of delivery, the full-term infants were dividedinto vaginal delivery group (n=22) and cesarean section group (n=23). Healthy children were divided into different agegroups:28 days to 12 months (n=25), 1-3 years (n=26), and 3-6 years (n=28). Lymphocyte subsets were examined byflow cytometry. The influencing factors including delivery method, sex, and age, which might have an effect on the lymphocyte subsets, were analyzed. Results There were significant differences in T and Ts cell counts, percentage of Bcells, and percentage and count of natural killer (NK) cells between the full-term infants of vaginal delivery and cesareansection (P<0.05). The absolute counts and percentages of different lymphocyte subsets showed no significant differences between males and females in healthy children (P>0.05). The counts of all lymphocyte subsets except Ts and NK cellsvaried significantly between different age groups (P<0.05). Conclusions Lymphocyte subsets in children under 6years of age are more profoundly affected by age. Delivery method is also a contributing factor in newborn infants. Thereference range of lymphocyte subsets in children should be established for different age groups.