Effects of caffeine and phosphodiesterase inhibitors on activation of neonatal T lymphocytes.

Caffeine and selective PDE inhibitors are widely used in clinical management of preterm and term neonates. However, little is known about how these compounds interact with the neonatal adaptive immune system. We aimed to describe the effects of caffeine, milrinone and sildenafil on the activation and cytokine production of T cells from umbilical cord blood (UCB) compared to adult peripheral blood (APB). We isolated mononuclear cells from 10 APB and 6 UCB samples. We assessed intracellular cytokine production (IFN-γ, IL-2, IL-4, IL-6, IL-17) of stimulated CD4 cells and parameters of calcium influx and ROS production following treatment with caffeine, milrinone, sildenafil, dbcAMP or a specific A2A receptor antagonist, ZM241385 using flow cytometry. In ABP, only ZM241385 caused a 1.14-fold increase in calcium influx, while all compounds increased calcium influx in UCB. This effect was more pronounced in case of caffeine (1.41-fold) and dbcAMP (1.3-fold) compared to milrinone (1.22-fold), sildenafil (1.23-fold) or ZM241385 (1.23-fold). Intracellular levels of the studied cytokines were unaffected by the applied compounds in both APB and UCB samples. Caffeine increases calcium influx upon activation in neonatal T lymphocytes to a larger extent than milrinone or sildenafil. This effect appears to be mediated primarily via increased cAMP levels rather than A2A receptor inhibition. Overall, the application of caffeine, sildenafil or milrinone does not appear to have immunosuppressive effects on neonatal T cells.