Differential neutrophil chemotactic response towards IL-8 and bacterial N-formyl peptides in term newborn infants

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.

Key words:

• Chemotaxis
• chemoattractants
• fMLP
• innate immunity
• IL-8
• neutrophils
• newborn infants

Acknowledgements

The authors would like to thank Cecilia Ewald and Lisa Strömbäck for collecting blood samples and Lena Gröndahl and Annica Hult for laboratory assistance.

Disclosure statement

The authors declare that they have no financial or non-financial competing interests.

Funding

The study was supported by grants from HKH Kronprinsessan Lovisas förening för barnsjukvård/Stiftelsen Axel Tielmans minnesfond, Stiftelsen Samariten [72X-04998], Stockholm, and Gillbergska stiftelsen Uppsala, Sweden.