Uptake of extracellular calcium by neonatal neutrophils

Neutrophils from human neonates exhibit abnormalities of plasma membrane and cytoskeletal dependent functions such as chemotaxis, deformability, and lectin capping. The uptake of extracellular calcium by neutrophils is a key early event in neutrophil activation and in the optimal performance of these functions. We found that neonatal and control neutrophils acquire extracellular radioactive calcium comparably under most experimental conditions. No differences (P greater than 0.05) were seen between neonatal and control neutrophils following stimulation with soluble sodium fluoride, N-formyl-methionyl-L-leucyl-L-phenylalanine, dimethylsulfoxide, and opsonized zymosan particles. However, the uptake of calcium by resting (unstimulated) neutrophils was significantly less (P less than 0.0001) by neonatal cells. The kinetics of calcium uptake by neonatal and control neutrophils were similar both at rest and following stimulation for 15 min with sodium fluoride. Although additional studies will be necessary to completely define the ionic events involved in the chemotaxis of neonatal neutrophils, it seems unlikely that the abnormal mobility of these cells is due simply to an inability of neonatal neutrophils to acquire extracellular calcium in response to cellular stimulation.