| Popis: |
Respiratory syncytial virus (RSV) is the most common cause of recurrent respiratory infections in newborns and infants by their second year of life. Although RSV predominantly induces Th1 type of immune response, it has also ability to provoke Th2 response, and it has been discussed as possible cause of childhood triggered asthma. Each of those immune responses is related with a production of specific cytokines and chemokines. Th1 is associated with production of IFN-γ and related chemokines CXCL10 and CXCL9, whereas Th2 is characterized by higher production of IL-4 and related chemokines CCL17 and CCL22. Chemokines are responsible for the recruitment of lymphocyte subpopulations via CXCR3 and CCR4 receptors, therefore driving predominant Th1 or Th2 immune response in infected tissue. Our previous results showed a disproportion in Th1/Th2 associated chemokine production between acute RSV infection and other respiratory viral infections. This was accompanied with higher expression of CCR4 receptor on helper and higher CXCR3 receptor upon cytotoxic peripheral blood T cells. T cells can be further distinguished into those that already encountered an antigen (memory T cells) and those that never encountered an antigen (naïve T cells). To analyze contribution of individual T cell subpopulations in the expression of CCR4 and CXCR3, we collected peripheral blood samples from infants with acute RSV infection, other respiratory viral infections and age matched healthy controls. Isolated PBMCs were stained with mAbs for CD3, CD4, CD45Ro, HLA- DR, CCR7 and naïve/memory T cells were acquired. Additional subpopulation of effector memory (CD45Ro+CCR7-) and central memory (CD45Ro+CCR7+) were analyzed for CXCR3 or CCR4 receptor expression. In all tested groups, much lower percentages of both helper and cytotoxic T cells were positive than negative for CD45Ro, but we haven’t found any difference between infected infants and healthy controls. In infected infants, higher percentages of CD45Ro+ cytotoxic T cells had CXCR3 receptor compared to healthy controls. No difference in percentages of effector memory (EM) helper and cytotoxic T cells bearing either CXCR3 or CCR4 between tested groups was observed. Percentage of CXCR3+ central memory (CM) helper T cells was elevated in all respiratory viral infections compared to healthy controls. On the other hand, there was higher percentage of CCR4+ CM helper T cells only in RSV infected infants. Higher percentages of CM helper T cells expressing CCR4 indicate skewing of immune response toward Th2 implicating inefficient adaptive immune response that could explain recurrent infection through infancy. |
