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

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.

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.

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.

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.

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.