Pediatrics International (2007) 49, 40–47 doi: 10.1111/j.1442-200X.2007.02296.x Recurrent respiratory infections (RRI) in infants and children are among the most common causes of counselling and admissions to hospital. Furthermore, they are often responsible for significant morbidity, as measured by school days lost, as well as mortality. 1 Several factors can play an important role in the genesis of the episodes of RRI, that can act alone or together: climatic or enviromental factors (indoor and outdoor pollution exposures), anatomic or functional alterations in the respiratory tract, atopy, infectious and non-infectious diseases (for instance HIV, cystic fibrosis, gastroesophageal reflux), passive smoke exposure, male gender, low bodyweight infant and poor socioeconomical condi- tions with malnutrition. An important role is played by early socialization in addition to the reduction of breast-feeding. 1,2 Among the predisposing factors for the genesis of the pedi- atric RRI we can consider not only the environmental ones but also transient or persistent immune system deficiencies. 1 A true immune deficiency is rare and the first cause of RRI is childhood itself; 2 both humoral and phagocytic immunity reach their best efficacy during the fifth or sixth year of age. 3,4 The World Health Organization classifies the primitive immu- nodeficiencies into four groups: 5 humoral or B-cell defects, cellular or T-cell defects, immunodeficiencies due to relevant illnesses, and non-specific immunity deficiencies. Phagocyto- sis, that is part of the non-specific immunity together with the complement system, is the process during which a cell enve- lopes, ingests and destroys microorganisms, cells or other for- eign particles. Therefore, in the suspicion of a non-specific immunity deficiency in a child with RRI, it is also important to evaluate chemotaxis, phagocytosis (FAG) and the reactive oxygen intermediates (ROI) production (necessary for the destruction of the ingested microorganism), besides an evalu- ation of the complement system. The aim of the present study was to evaluate the impact of the possible alterations, anomalies or dysfunctions of FAG and ROI production on pediatric RRI, by the analysis of the phagocytosis activity (FAG test) and the reactive oxygen Original Article Recurrent respiratory infections and phagocytosis in childhood MASSIMILIANO DON, 1 LOLITA FASOLI, 1 VIVIANA GREGORUTTI, 1 FEDERICA PISA, 2 FRANCESCA VALENT, 2 MARIO PRODAN 3 AND MARIO CANCIANI 1 Departments of 1 Pediatrics and 2 Hygiene, School of Medicine DPMSC, University of Udine, Udine and 3 Istituto per l’Infanzia ‘Burlo Garofolo’, University of Triest, Triest, Italy Abstract Background: About 10% of pre-school children has recurrent respiratory infections (RRI), which could be related to environmental and/or immunological factors. The aim of the present study has been to evaluate the impact of phagocytosis (FAG) and reactive oxygen intermediates (ROI) production deficiencies on pediatric RRI by the measurement of FAG and ROI activity of the polymorphonuclear neutrophils. Methods : Serum immunoglobulins, IgG subclasses, lymphocytic subpopulations, FAG and ROI tests were measured in 90 children with RRI, in a moment of well-being and off all medications for at least 4 weeks. FAG and ROI tests were also measured in 19 healthy children. Results: FAG (91.4 ± 11.5%) and ROI (81.8 ± 17.5%) of patients resulted in significantly decreased measure- ments compared to the control values (95.2 ± 1.8% and 89.7 ± 4.8%, respectively). No significant difference was manifest between the mean values of FAG and ROI tests among the patients when they were divided for age (above and below 6 years). A significant decreased likelihood of abnormal ROI (odds ratio, 0.3; 95% confidence interval, 0.07–0.97) was found in the patients with low IgA. Conclusions : The authors’ results permit only to suppose an etiological role of FAG and ROI deficiencies of polymorphonuclear neutrophils in the genesis of pediatric RRI, irrespective of the age of the patients, and further studies are necessary for confirmation. Key words childhood, phagocytosis, recurrent respiratory infections. Correspondence: Massimiliano Don, MD, Pediatric Department, School of Medicine DPMSC, University of Udine, P.le S. Maria della Misericordia, 33100 Udine, Italy. Email: max.don@libero.it Received 9 July 2005; revised 28 September 2005; accepted 24 October 2005.