Differential IFN-γ production by adult and neonatal blood CD56+ natural killer ( NK) and NK-like- T cells in response to Trypanosoma cruzi and IL-15.

Early interferon-gamma ( IFN-γ) release by innate cells is critical to direct type 1 immune response able to control intracellular pathogens like Trypanosoma cruzi. Although CD56^bright natural killer ( NK) cells are reported to be potent early IFN-γ producers, other CD56⁺ cells like CD56^dim NK cells and NK-like T cells have recently been shown to also release IFN-γ. We have here studied the contribution of each CD56⁺ lymphocyte populations in early IFN-γ production in both adults and neonates. On this purpose, we analysed the kinetics of IFN-γ production by RT- PCR, ELISA and flow cytometry from 2 h onwards after T. cruzi and IL-15 stimulation and sought for the responding CD56⁺ cells. CD56^bright and CD56^dim CD16⁻ NK cells were the more potent IFN-γ early producers in response to IL-15 and parasites in adults and neonates. In both age groups, the majority of IFN-γ producing cells were NK cells. However, on the contrary to neonates, CD3⁺ CD56⁺ NK-like T cells and CD3⁺ CD56⁻ 'classical' T cells also contributed to early IFN-γ production in adults. Altogether, our results support that whereas NK cells responded almost similarly in neonates and adults, cord blood innate CD56⁺ and CD56⁻ T cells displayed major quantitative and qualitative defects that could contribute to the well-known neonatal immune immaturity. [ABSTRACT FROM AUTHOR]