The immune system of a child has a degree of immaturity that is maintained until 6-7 years of age. Immaturity may be due to age-related functional disorders in the immune response. A healthy child can contract a series of infections which contribute to the maturation of the immune system during the pre-pubertal period. If repeated infections with prolonged or severe complications occur during childhood, the presence of an immunodeficiency should then be considered. Much more frequent than primary immunodeficiency are recurrent infections (frequently involving the upper respiratory tract), which are less severe and occur under the conditions of an immune system with no apparent major defects. A child can present with 4 to 8 episodes of respiratory infections within a year, during the first 5 years of its life. The average duration of infection is 8 days and up to 2 weeks; if the child presents with 3 episodes of acute infections over a period of 6 months, the respiratory infections are then considered recurrent. The aim of this study was to identify the immunological changes or deviations that cause this clinical syndrome in children. For this purpose, 30 children with recurrent respiratory infections and 10 healthy children were included. Immunoglobulin levels were examined and immunophenotyping was performed. We found that the serum immunoglobulin levels were in the normal range in 70% of the children. On the contrary, our data revealed changes in peripheral cell populations, the most important being the decrease in the T-cluster of differentiation (CD)8+ and total B cell percentages and the increase in the number of memory B cells. The data obtained herein indicated that the decrease in the number of total B cells was mainly due to the decrease in the number of naive IgD+ B cells. On the whole, the findings of this study indicate that recurrent respiratory infections may be associated with an altered cellular immune response. In such situations, the investigation of immunological parameters, such as T and B cell subtypes could complete the clinical diagnosis and guide the treatment strategy, thus increasing the quality of life of patients.
Keywords: double-negative T cells; memory B cells; recurrent respiratory infections.