Abnormal expansion of peripheral helper T cells in primary immune thrombocytopenia

. Notably, persistently elevated Tph levels were observed in patients who were non-responsive to dexamethasone. Furthermore, plasma interleukin-21 levels declined in parallel with Tph reduction following dexamethasone treatment, and were positively correlated with Tph frequencies in untreated, newly diagnosed ITP patients, consistent with Tph-associated B-cell helper activity. Collectively, these findings identify Tph cells as a potential indicator of extrafollicular B-cell activation in ITP and highlight their relevance to dexamethasone therapeutic responsiveness.