T cell receptor V gene usage by CD4+ and CD8+ peripheral blood T lymphocytes in immune thrombocytopenic purpura

AIM: To identify T cell expansions, i.e. increased frequencies of T cells using a particular T cell receptor (TCR) V alpha or V beta gene segment, in patients with immune thrombocytopenic purpura (ITP). METHODS: The TCR repertoires of CD4+ and CD8+ peripheral blood lymphocytes of 16 patients with chronic ITP were analysed by staining with a panel of anti-TCR V alpha and V beta antibodies followed by flow cytometry. RESULTS: Four of the 16 patients exhibited a total of 6 expansions of CD8+ T cells using a particular V beta segment, but no expansions were detected in the CD4+ subset. For three of the expansions where a follow-up blood sample after treatment with intravenous immunoglobulin was available, only one expansion remained. CONCLUSION: Overall T cell expansion frequency was the same as in healthy individuals. However, the presence of expansions that normalized with treatment suggests the presence of specific T cells implicated in the pathogenesis of ITP.