Abstract
Background: A prerequisite for an effective innate immunity is the migrative ability of neutrophils to respond to inflammatory and infectious agents such as the intermediate interleukin (IL)-8 and the end-target formyl-methionyl-leucyl-phenylalanine (fMLP) chemoattractants. The aim was to study the chemotactic capacity of neutrophils from newborn infants and adults in response to IL-8 and the bacterial peptide fMLP.Methods: In the under-agarose cell migration assay, isolated leukocytes from healthy adults and from cord blood of healthy term newborn infants were studied with dose responses towards IL-8 and fMLP. The same number of leukocytes (1 × 105 cells), with the same distribution of neutrophils and monocytes, were analyzed in neonates and adults. Chemotaxis was distinguished from randomly migrating neutrophils, and the neutrophil pattern of migration, i.e. the migration distance and the number of migrating neutrophils per distance, was evaluated.Results: In comparison to adults, fewer neutrophils from newborn infants migrated towards IL-8 and for a shorter distance (P < .01, respectively). The number of neutrophils migrating to different gradients of fMLP, the distance they migrated, and the correlation between the number and the distance were the same for neonates and adults. Random migration did not differ in any instance.Conclusion: Chemotaxis of neutrophils from newborn infants was as co-ordinated as neutrophils from adults in response to fMLP, whereas the response to IL-8 was reduced. The differential response of neutrophils from neonates to intermediate and end-target chemoattractants could indicate a reduced infectious response.
Highlights
Neutrophils are the most abundant cells of the innate immune system
We observed that neutrophils from newborn infants have a differentiated chemotactic response towards intermediate and end-target chemoattractants
With the under-agarose migration assay we demonstrated that neutrophils from newborn infants are as co-ordinated as neutrophils from adults in response to fMLP
Summary
Neutrophils are the most abundant cells of the innate immune system. They are one of the first inflammatory cells to migrate towards the site of invading micro-organisms. A reduced capacity to increase neutrophil production [3], together with an observed decreased chemotaxis into infected sites [4,5], makes the newborn infant vulnerable to bacterial infections. The aim was to study the chemotactic capacity of neutrophils from newborn infants and adults in response to IL-8 and the bacterial peptide fMLP. Methods: In the under-agarose cell migration assay, isolated leukocytes from healthy adults and from cord blood of healthy term newborn infants were studied with dose responses towards IL-8 and fMLP. The differential response of neutrophils from neonates to intermediate and end-target chemoattractants could indicate a reduced infectious response
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