Expression of CD154 (CD40L) on stimulated T lymphocytes in patients with idopathic thrombocytopenic purpura.

OBJECTIVES

The role of CD40-CD154 (CD40L) interaction in T cell-dependent humoral immune response is strongly established. Increased expression of CD154 on stimulated T cells is observed in rheumatic diseases and is associated with disease activity. We investigated the expression of CD154 on T cells from idiopathic thrombocytopenic purpura (ITP) patients and assessed the significance of CD154 expression in disease status.

METHODS

We enrolled 59 ITP patients, 23 healthy controls, and 19 patients with non-immune thrombocytopenia. Isolated mononuclear cells were stimulated in RPMI medium containing phorbol myristate acetate (PMA) (5 ng/mL) and ionomycin (500 ng/mL) for 2 h at 37°C. The expression of CD154 on CD4(+)T cells was evaluated using flow cytometry and serum soluble CD40L levels were measured.

RESULTS

In ITP patients, the percentage of CD4(+) CD154(+) cells and mean fluorescence intensity (MFI) of CD154 on activated CD4(+)T cells was not different from that in the healthy controls and non-immune thrombocytopenia patients. Additionally, the percentage and expression level of CD154 was not different between ITP patients with low platelet counts (<50 000/μL) and those with 50 000/μL or more. Soluble CD40L levels were significantly lower in ITP patients with low platelet counts than in healthy controls, but were not correlated with CD154 expression.

CONCLUSION

Increased CD154 expression on CD4(+)T cells was not observed in ITP patients and was not related with low platelet counts. Overexpression of CD154 on CD4(+)T cells is unlikely to be central to the pathogenesis of ITP, and other immune dysfunctions should be targeted for therapy purposes.