Сhanges in functional activity of peripheral blood neutrophils in young children with recurrent respiratory infection

Neutrophils characterized by high mobility and ability for quick and accurate reresponse upon homeostatic changes. These changes primarily occur at the inflammation site. The pathogen elimination depends on the phagocytic activity of neutrophils. The data from past decades have revisited the role of neutrophils and their involvement in changing the human cellular and humoral immunity. Neutrophils are not only effector cells, but also regulatory cells of both innate and adaptive immunity. Our purpose was to study phagocytic activity and parameters of oxygen-dependent metabolism of peripheral blood neutrophils in young children with recurrent respiratory infections. We examined 111 children aged 1-3 years with recurrent respiratory infections over the period of clinical remission. The control group consisted of 24 healthy children aged 1-3 years. Phagocytic activity of peripheral blood neutrophils was studied by the latex test. Luminol-dependent chemiluminescence of blood neutrophils was studied according to de Sole et al. (1983). The study of phagocytic indexes of peripheral blood neutrophils in the children with recurrent respiratory infections has revealed a decrease in the number of actively phagocytizing cells and preservation of their absorptive capacity. Studies of luminol-dependent chemiluminescence in peripheral blood neutrophils in children with recurrent respiratory infections revealed changes in oxygen-dependent metabolism depending on the clinical variant of complicated infection. In the group of children with broncho-obstructive syndrome, the background chemiluminescence parameters of peripheral blood neutrophils were characterized by faster time to chemiluminescence curve peak. Chemiluminescence indices induced by opsonized zymosan showed a lower time of reaction to stimuli, decreased intensity of “respiratory burst”-associated luminescence, and decreased trend for activation index of peripheral blood neutrophils. Study of luminol-dependent chemiluminescence peripheral in blood neutrophils in children with hypertrophy of pharyngeal tonsils did not reveal changes in the background chemiluminescence levels. Chemiluminescence evaluation upon stimulation of peripheral blood neutrophils by opsonized zymosan caused a decrease in the stimulated response time, lower maximal “respiratory burst”, and decrease in AUC chemiluminescence. Thus, kinetics of spontaneous chemiluminescent response in peripheral blood neutrophils is impaired.in children with broncho-obstructive syndrome. Similarly, the in vitro neutrophil stimulation showed changes in chemiluminescent response kinetics and decreased reserve of oxygen-dependent metabolic capacity. In the children with hypertrophy of pharyngeal tonsil, we observed changes in chemiluminescent response of peripheral blood neutrophils only after opsonized zymosan induction. Compensatory metabolic capacity of peripheral blood neutrophils was retained in the opsonized zymosan stress tests. The study results showed unidirectional changes in peripheral blood neutrophil phagocytic activity parameters both in children with broncho-obstructive syndrome, and in children with pharyngeal tonsil hypertrophy and recurrent respiratory infection.

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