Features of the neutrophil granulocyte phenotype in children with infectious mononucleosis

Abstract

The course of infectious diseases caused by viruses, and their common outcome is determined by the activity of the inflammatory reaction which occurs both at the local and systemic levels. However, the features of neutrophil functions during inflammatory reaction are virtually unknown in the patients with infectious mononucleosis (IM), caused by Epstein–Barr virus (EBV). Hence, the aim of our study was to evaluate some characteristics of phenotypic spectrum of blood neutrophils in children with IM. Patients and methods. We examined 84 children aged 3 to 11 years with EBV infection with moderate or severe clinical course of the disease. All patients exhibited a positive test for EBV DNA in blood lymphocytes and appropriate serological markers of acute EBV infection. The control group consisted of 40 conditionally healthy children at the similar age range. The study of neutrophil phenotype was carried out by flow cytometry using direct immunofluorescence of whole peripheral blood samples. A study of the neutrophil phenotype with a combination of two functional antigens (CD64 and CD32) has revealed that in children with IM, regardless of age, the main fraction of blood neutrophils are double-negative cells, whereas in healthy children it consists of CD64-CD32+ neutrophils. The main fraction of neutrophils in the paired combination of CD64 and CD11b antigens in sick children aged 3-6 and 7-11 years was similar to the healthy controls (CD64-CD11b+), but with a change in the content of minor cell fractions. The number of CD64-CD15+ neutrophils (main fraction of cells in healthy children) proved to be significantly reduced in the IM patients of both age groups. However, we have revealed a marked increase in the level of double-negative cells for the CD64 and CD15 antigens. At the same time, the content of double-negative neutrophils for these markers was also increased in IM children of both age groups. The cells with CD11b-CD15+ and CD11b+CD15+ phenotypes comprised the main fractions in IM, as studied by a paired combination of CD11b and CD15 antigens; in healthy children – only CD11b+CD15+ neutrophils are detected. The phenotypic changes of neutrophils during IM suggest a decreased migratory ability of cells with high activity of proinflammatory functions. The established ontogenetic features of the neutrophil phenotype are significantly changed in the children with IM, probably, due to specific immunopathogenesis of the viral infection. The detected changes in phenotypic composition of neutrophils associated with IM may be caused both by the features of protective reaction of innate immune cells and pathogenic effects of the virus itself upon blood neutrophils.