IL-2 Expression and T lymphocyte Phenotyping in Young Children Suffering from Upper Respiratory Tract Infection with Streptococcus Pyogenes.

T cells are components of adaptive immunity and are involved in the resolution of respiratory infections, which are a major cause of morbidity and mortality in young children worldwide. Activation and differentiation of T cells is given mostly by the cytokine IL-2. This study aimed to determine the phenotype of T cells and IL-2 expression in children suffering from upper respiratory tract infection with Streptococcus pyogenes (S. pyogenes). For this purpose, IL-2 expression at its gene and protein levels and quantitation of CD4(+) and CD8(+) T lymphocytes were assessed in children aged 0-5 years old suffering from upper respiratory tract infection with S. pyogenes and healthy children of the same age. Children with S. pyogenes infection had a higher expression of IL-2 gene and a lower level of this cytokine expression at protein level than healthy children. The numbers of CD4(+) T lymphocytes were similar among the groups. In contrast, difference in the numbers of CD8(+) T lymphocytes among the groups was found. We conclude that infections by S. pyogenes in young children lead to an increased expression of IL-2 mRNA.