IL-2 and the thymus/weight index are inversely correlated with gestational age: a sign of Th1/Th2 imbalance in preterm infants and a possible connection with atopic dermatitis

<b>Background.</b> Understanding the reason for the decrease in atopic dermatitis risk in preterm patients may be crucial for the development of prophylaxis and therapeutic measures. The hypotheses include a change in T-helper1/T-helper2/T-helper17 balance, thymus development, and intestinal colonization. This study was designed to compare these parameters between preterm and term patients. <b>Methods.</b> The investigated population comprised 28 preterm and 19 term-born patients. On the 7^th day of life, T-helper1/T-helper2/T-helper17 cytokine concentrations were assessed, thymus ultrasonographic examination was performed, and the stool was examined for the presence of pathogenic bacteria. The last two procedures were repeated at 37 weeks of post-menstrual age in the preterm group. <b>Results.</b> There were no significant differences in the concentrations of interferon-γ, tumour necrosis factor-a (TNFa), interleukin (IL)-2, IL-6, or IL-10 after mitogen stimulation between the preterm and term groups. A negative correlation was found between IL-2 and the week of gestation at birth (r_s= -0.466, p=0.038) and thymus/weight ratio and week of gestation at birth (r_s= -0.592, p=0.006). IL-6 was negatively correlated with birth weight in preterm group (r_s -0.694, p=0.008), whereas IL-10 positively with birth weight in term group (r_s 0.775, p=0.041). Correlations of other investigated cytokines were statistically insignificant. The levels of IL-2 and interferon-γ after phytohemagglutinin stimulation were greater in the subgroup with pathogenic bacteria in the stool at birth (381.38 (148.7-727.4) vs. 13.23 (7.98-197.8) pg/ml; p=0.049; 17.49 (6.53-30.54) vs. 3.37 (1.03-9.82) pg/ml; p=0.037), whereas no significant differences were found between the levels of IL-6, IL-10 or TNFa. <b>Conclusions.</b> The observed associations may indicate an altered pattern of immunological development in preterm and term children.