Development of natural killer cell function in the human fetus

Area of Science:

• Immunology
• Developmental Biology
• Perinatology

Background:

• Natural killer (NK) cells are crucial for innate immunity.
• Understanding the development of NK cell activity in utero is important for assessing fetal and neonatal immune competence.

Purpose of the Study:

• To investigate the presence and functional capacity of NK cells in human fetuses and premature infants.
• To determine the stage of gestation at which NK cell activity emerges.
• To assess the potential for enhancing NK cell function with interferon-alpha (IFN-alpha).

Main Methods:

• NK cell activity was assessed using a 4-hour 51Cr-release assay against the K-562 cell line.
• Samples were obtained from premature infants (28-33 weeks gestation) and fetuses (9-22 weeks gestation).
• In vitro IFN-alpha treatment was applied to evaluate its effect on NK cell cytotoxicity.

Main Results:

• Premature infants exhibited NK cell activity, though at lower levels than full-term newborns or adults.
• Four out of eleven fetuses showed NK cell cytotoxicity against K-562 targets, primarily from fetal liver cells, as early as 9 weeks gestation.
• Fetal bone marrow, spleen, and thymus showed minimal to no NK cell activity.
• IFN-alpha treatment augmented NK cell activity in both premature infants and fetuses, but only in cells with pre-existing spontaneous activity.

Conclusions:

• Human NK cell activity originates during intrauterine development, detectable as early as 9 weeks gestation in fetal liver.
• Premature infants possess functional NK cell capacity, indicating a foundational level of innate immunity.
• IFN-alpha serves as a potential therapeutic agent to enhance NK cell function in immature immune systems.