Characteristics of CD4+CD25+ regulatory T cells in the peripheral circulation of patients with head and neck cancer

Patients with squamous cell carcinoma of the head and neck (SCCHN) have depressed antitumour immunity. The presence of CD4+CD25+ (T(reg)) cells in these patients might be, in part, responsible for downregulation of antitumour immune responses. To evaluate the frequency and characteristics of T(reg) in the peripheral circulation of patients with SCCHN, we used multicolour flow cytometry. Expression of CCR7, CD62L, ζ chain and Annexin V binding to T(reg) and non-T(reg) CD4+ lymphocyte populations were evaluated. T(reg) were confirmed to be Foxp3+ and GITR+. The T(reg) frequency was significantly elevated in patients with active disease and those with no evidence of disease (NED) following curative therapies. Both T(reg) and non-T(reg) CD4+ T cells in patients were significantly enriched in CCR7(−) and CD62L(−) cell subsets. Although T(reg) in patients contained a higher proportion of double negative (CCR7(−)CD62L(−)) cells, the majority of T(regs) were CCR7(−)CD62L+. The proportion of Annexin V+CD4+ T cells was higher in patients (P<0.00005) than normal controls (NC), and T(reg) were significantly more sensitive to apoptosis than non-T(reg) in patients and NC. Expression of ζ was reduced in all subsets of CD4+ T cells obtained from patients vs NC. The data suggest that T(reg) in patients with SCCHN largely contain T cells with the ‘effector’ phenotype, which bind Annexin V and have low ζ expression, consistent with their activation state and a rapid turnover in the peripheral circulation.