Dissecting the defects in the neonatal CD8 T-cell response.

The neonatal period presents a complex scenario where the threshold of reactivity toward colonizing microbiota, maternal antigens, autoantigens, and pathogens must be carefully moderated and balanced. CD8 T cells are critical for the response against intracellular bacteria and viruses, but this immune compartment maintains altered function relative to adult counterparts because of the unique challenges which infants face. Here, we review our current understanding of the factors which may promote the attenuation and altered function of the neonatal CD8 T-cell response and potential avenues for future study. Specifically, we have focused on the neonatal CD8 T-cell ontogeny, memory formation, TCR structure and repertoire, TCR inhibitory receptors, and the clinical implications of altered neonatal CD8 T-cell function. Special emphasis has been placed on examining the response of preterm neonates relative to term neonates and adults.