Introduction: Pneumonitis, characterized by large numbers of neutrophils, is an important feature of meconium aspiration syndrome (MAS). The mechanism underlying the neutrophil influx is unknown. This study evaluated if meconium was chemotactic and if this was related to the presence of IL-8.

Methods and Results: The chemotactic effect of meconium samples(n = 8), collected postnatally and shown to be sterile, on cord blood neutrophils of babies (ga 34-40wks) was tested in a Boyden chamber. Meconium stimulated chemotaxis (Fig 1). Migration of neutrophils was significantly increased in all meconium samples as compared to random migration, but migration varied between samples (Fig 1). Neutrophil migration was maximal at a meconium concentration of 5 mg/ml. IL-8 was present in all meconium suspensions in a concentration varying between 500 and 4000 pg/ml. A concentration dependent inhibition of meconium-induced migration and IL-8 induced migration by anti-IL-8 was observed (respectively 70±3 μm vs 47±2 μm and 99±2μm vs 52±2 μm; P<0.001).

figure 1

Fig 1

Conclusion: IL-8 in meconium induces chemotaxis of and this mechanism may play a role in the pathogenesis of pneumonitis in MAS.