PKC? activation promotes maturation of cord blood T cells towards a Th1 IFN-? propensity

A significant number of babies present transiently with low protein kinase C zeta (PKC?) levels in cord blood T cells (CBTC), associated with reduced ability to transition from a neonatal Th2 to a mature Th1 cytokine bias, leading to a higher risk of developing allergic sensitisation, compared to neonates whose T cells have 'normal' PKC? levels. However, the importance of PKC? signalling in regulating their differentiation from a Th2 to a Th1 cytokine phenotype propensity remains undefined. To define the role of PKC? signalling in the regulation of CBTC differentiation from a Th2 to a Th1cytokine phenotype we have developed a neonatal T cell maturation model which enables the cells to develop to CD45RA(-)/CD45RO(+) T cells while maintaining the Th2 immature cytokine bias, despite having normal levels of PKC?. The immature cells were treated with phytohaemagglutinin, but in addition with phorbol 12-myristate 13-acetate (PMA), an agonist which does not activate PKC?. This was compared to development in CBTC in which the cells were transfected to express constitutively active PKC?. The lack of PKC? activation by PMA was monitored by western blot for phospho-PKC? and translocation from cell cytosol to the membrane by confocal microscopy. The findings demonstrate that PMA fails to activate PKC? in CBTC. The data show that CBTC matured under the influence of the PKC stimulator, PMA, maintain a Th2 cytokine bias, characterised by robust IL-4 and minimal interferon gamma production (IFN-?), and lack of expression of transcriptional factor, T-bet. This was also reflected in the production of a range of other Th2/Th1 cytokines. Interestingly, introduction of a constitutively active PKC? mutant into CBTC promoted development towards a Th1 profile with high IFN-? production. The findings demonstrate that PKC? signalling is essential for the immature neonatal T cells to transition from a Th2 to a Th1 cytokine production bias.