Defective membrane potential changes in neutrophils from human neonates

Area of Science:

• Immunology
• Cell Biology
• Neonatal Medicine

Background:

• Polymorphonuclear leukocytes (PMN) are crucial for innate immunity.
• Human neonates exhibit a profound defect in PMN chemotaxis.
• The underlying mechanism of this neonatal chemotactic defect remains unclear.

Purpose of the Study:

• To investigate the mechanism of impaired chemotaxis in neonatal PMN.
• To examine membrane potential changes and intracellular calcium alterations in response to chemotactic factors.
• To compare the responses of neonatal and adult PMN.

Main Methods:

• Utilized formyl-methionyl-leucyl-phenylalanine (FMLP) as a chemotactic factor.
• Measured PMN membrane potential changes using the cyanine dye DiOC5(3).
• Assessed intracellular free calcium levels using the calcium-sensitive probe Quin 2/AM.

Main Results:

• Adult PMN showed significant membrane potential changes (31%) and increased intracellular calcium (51%) upon FMLP stimulation.
• Neonatal PMN displayed minimal membrane potential changes (1-2%) and a significantly reduced increase in intracellular calcium (32%; P < 0.01).
• A strong correlation was observed between impaired membrane potential changes and reduced calcium signaling in neonatal PMN.

Conclusions:

• Neonatal PMN are unable to adequately alter membrane potential in response to inflammatory mediators.
• This inability to modulate membrane potential likely contributes to the observed defect in intracellular calcium flux.
• The findings suggest that impaired membrane potential regulation is a primary cause of the profound chemotactic defect in human neonatal PMN.