However, in vitro-activated B cells downregulated CD73 expression, mainly produced 59-AMP, and inhibited T-cell proliferation and cytokine production. These B cells acquire the ability to restrict potentially harmful effects of activated T cells. Thus, B cells emerge as a key regulatory component of T cell-B cell interactions, and their dual regulatory activity is mediated by the products of ATP hydrolysis, 59-AMP, and ADO. (Blood. 2013;122(1):9-18)
Purpose
Regulatory T cells (Treg) accumulate in tumor tissues and the peripheral blood of cancer patients and may persist after therapies. This cross-sectional study examines effects of adjuvant chemo-radiotherapy (CRT) on Treg numbers and function in head and neck squamous cell carcinoma (HNSCC) patients.
Experimental design
The frequency and absolute numbers of CD4+, ATP-hydrolyzing CD4+CD39+ and CD8+ T cells and expression levels of CD39, CD25, TGF-β-associated LAP and GARP on Treg were measured by flow cytometry in 40 healthy donors (NC) and 71 HNSCC patients (29 untreated with active disease (AD); 22 treated with surgery; 20 treated with CRT). All treated subjects had no evident disease (NED) at the time of phlebotomy. In an additional cohort of 40 subjects with AD (n=15), NED (n=10) and NC (n=15), in vitro sensitivity of CD4+ T cell subsets to cisplatin and activation-induced cell death (AICD) was tested in Annexin V-binding assays.
Results
CRT decreased the frequency of circulating CD4+ T cells (p<0.002) but increased that of CD4+CD39+ Treg (p≤0.001) compared to untreated or surgery-only patients. Treg frequency remained elevated for >3 years. CRT increased surface expression of LAP, GARP and CD39 on Treg. In vitro, Treg were resistant to AICD or cisplatin but conventional CD4+ T cells (Tconv) were not. CRT-induced Treg from AD or NC subjects up-regulated pro-survival proteins, while Tconv up-regulated pro-apoptotic Bax.
Conclusions
Highly suppressive, cisplatin-resistant Treg increase in frequency and persist after CRT and could be responsible for suppression of anti-tumor immune responses and recurrence in HNSCC.
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