Abstract Text: Viral infection is one of the top causes of neonatal morbidity and mortality. Cytotoxic CD8 T cells are necessary for the anti-viral immune response and have unique features in early-life. These include enhanced proliferation, but early cell death. To ascertain the functional properties of stimulated neonatal CD8 T cells, we quantified activation and cytotoxic molecule production compared to healthy young adult counterparts.
Naive CD8 T cells (CD8+CCR7+CD45RA+DAPI-) were sorted using Fluorescence-activated Cell Sorting (FACS) from whole blood of healthy young adults ( < 30 years) and full-term neonates at birth (cord blood). Cells were then stimulated with anti-human CD3 and CD28 in complete RPMI medium with IL-2. On days two and three after stimulation, cells were re-stimulated using Phorbol 12-myristate 13-acetate (PMA) and ionomycin for four hours. Cytokine secretion was prevented by adding Brefeldin A/Monensin. Cell surface molecules and intracellular cytokines were quantified using flow cytometry.
Activated neonatal CD8 T cells produced significantly increased TNFα and IL-2 after restimulation compared to their adult counterparts. Conversely, IFNγ production and expression of activation marker, CD25, and Fas ligand were not significantly different. Preliminary experiments show enhanced viability and decreased cytokine production in the presence of Rapamycin, an mTOR complex 1 inhibitor, in both neonatal and adult cells.
Increased TNFα and IL-2 production in neonatal CD8 T cells after 2-3 days of stimulation may indicate unique roles for these cytokines in early-life. Further work is needed to decipher molecular programs driving this phenotype and the roles of TNFα in early-life immunity.
