Objective: To explore the effect of peripheral blood T lymphocyte activation on the blood cells, tissue injury and the development of disease in patients with severe fever with thrombocytopenia syndrome (SFTS).
Methods: The expressions of CD69, HLA-DR, CD28 and CTLA-4 on peripheral blood T lymphocytes were determined dynamically by flow cytometry and the relationships between the above immune molecules and ALT, AST, leukocytes, platelets were analyzed respectively.
Results: The expressions of CD69 and HLA-DR on peripheral blood T lymphocytes in patients with SFTS were elevated significantly during the whole course of disease (P<0.05). CD28 expression on CD4(+); lymphocyte subset decreased in the early stage and gradually increased to the normal range. Meanwhile, CTLA-4 expression on T lymphocytes went up in the late stage of viral infection. The levels of serum ALT, AST, LDH and CK were significantly higher than the upper limit of the normal and the counts of WBC and PLT dropped to the lowest at the outset. But all of them returned back to the normal range gradually with the down-regulation of CD69 and HLA-DR and the up-regulation of CTLA-4 on T lymphocyte.
Conclusion: The overactivation of T lymphocytes may contribute to tissue injury and the high expression of CTLA-4 may be a negative feedback regulation to the overactivation of T lymphocytes, which plays an important role in immunoregulation of SFTS patients.