Altered circulating memory T cells in vitiligo cases followed NB‐UVB therapy

BACKGROUND: Vitiligo represents a commonly diagnosed autoimmune disease caused by the depletion of epidermal melanocytes. Many subsets of T cells contribute to vitiligo pathogenesis, including resident and circulating memory T cells. OBJECTIVES: To analyze the amounts of CD4(+) and CD8(+)memory T‐cell subsets in peripheral blood specimens from vitiligo patients and alterations caused by narrowband ultraviolet B (NB‐UVB) phototherapy. METHODS: Circulating CD4(+) and CD8(+) central memory T (T(CM)) and effector memory T (T(EM)) cell frequencies in 33 patients with non‐segmental vitiligo and 16 healthy donors were evaluated by flow cytometry. Related chemokine levels were also detected. RESULTS: Peripheral blood CD4(+) T(CM) and CD8(+) T(CM) counts were markedly reduced in vitiligo cases while they were higher in active vitiligo compared with stable vitiligo cases. Circulating CD8(+) T(CM) frequency in vitiligo was closely related to disease duration. Interestingly, CD4(+) T(CM) and CD8(+) T(CM) frequencies, alongside CXCL9 and CXCL10 amounts in peripheral blood of patients with vitiligo, were significantly decreased after NB‐UVB phototherapy. CONCLUSIONS: Decreased frequencies of circulating CD4(+) T(CM) and CD8(+) T(CM) by NB‐UVB suggest a possible immunosuppressive effect of phototherapy. The chemokines CXCL9 and CXCL10 are the bridge between circulating and skin resident memory T cells. NB‐UVB blocks the homing of circulating memory T cells into vitiligo lesions by down‐regulating CXCL9 and CXCL10. Targeting the above proteins could provide novel, durable treatment options to cure and prevent flares of this disease.