[Roles of CD8+ CD28- T regulatory cells in acute infectious mononucleosis in children].

OBJECTIVE

To explore the role of CD(8)(+)CD(28)(-) T regulatory cells (Tr) in the immunological pathogenesis of acute infection with Epstein-Barr virus in children.

METHODS

The present study enrolled 25 children with infectious mononucleosis (IM) and 25 age-matched healthy children. Flow cytometric analysis was performed to detect the percentage of CD(3)(+), CD(3)(+)CD(4)(+), CD(3)(+)CD(8)(+), CD(8)(+)CD(28)(+) by determining the ratio of positive cells in lymphocytes. Reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR were used to analyze IL-6, IL-10, IFN-gamma expression in CD(8)(+)CD(28)(-) Tr cells and ILT-3, ILT-4 expression in monocytes/macrophages.

RESULTS

The proportions of CD(8)(+)CD(28)(-)T cells in children with acute-phase IM was significantly higher than those in the controls (P < 0.01). The expression level of IL-6, IL-10, IFN-gamma, ILT-3, ILT-4 mRNA significantly increased compared to those of the controls (P < 0.01).

CONCLUSION

The CD(28) expressed on CD(8)(+) T cells in vivo is gradually lost with age and CD(8)(+)CD(28)(-) cells increase up 50% to adult. EBV can directly infect B cells, trigger CD(8)(+) CTL response and destroy the target cells to cause serious immunopathological lesion. Therefore we speculate that the expansion of CD(8)(+)CD(28)(-) Tr cells in children with IM may be an adaptive immune response to avoid serious inflammation and autoimmune reactions.