Granulocyte functions and changes in ability with age in newborns; Report no. 2: activation of granulocyte functions...

The aim of the present study was to examine the function of granulocytes in newborns from the perspective of granulocyte activation by cytokines.

Granulocytes were stimulated with tumor necrosis factor-alpha, granulocyte-macrophage colony stimulating factor (GM-CSF) or granulocyte colony stimulating factor, and the reactivity of granulocytes to these substances was then compared between newborns (umbilical cord blood, peripheral blood obtained at age 5 days and at age 1 month) and peripheral blood obtained from adults. In addition, the expression of cytokine receptors on the surface of granulocytes was measured for each age group.

The amplification of CD11b expression on the surface of granulocytes and suppression of l-selectin expression were weaker for cord blood regardless of which cytokine was added. In addition, the increases in the activity of intracellular elastase when stimulated with tumor necrosis factor-alpha or GM-CSF were significantly lower for cord blood. Moreover, the expression of GM-CSF receptors and granulocyte colony stimulating factor receptors on the surface of granulocytes was lower for cord blood, and this expression approached the level found in adults as age increased.

Granulocytes during early infancy exhibit low reactivity to inflammatory cytokines, and this was considered to be one of the factors contributing to the higher incidence of serious bacterial infections in infants.