Ultraviolet-induced alloantigen-specific immunosuppression in transplant immunity

Figure 1 Schema illustrating the postulated reactions in achieving alloantigen-specific immunosuppression by ultraviolet-B irradiation accompanied with alloantigen immunization. APCs, such as mature DC and LC, capture alloantigen. UV-B irradiation and subsequent IL-10 secretion will cause antigen presentation in a nonprofessional manner to induce antigen-specific immunosuppression. Immature DC presents alloantigen to CD4⁺ T cell, and then, Treg induction and IL-10 secretion arise. LC presents alloantigen to NKT cell, and IL-4 secretion subsequently occurs. Also, LC presents alloantigen to Foxp3⁺ Treg, and thereafter, Foxp3⁺ Treg proliferation and Treg induction are triggered. Hence, alloantigen-specific Treg, Foxp3⁺ Treg, IL-10 and IL-4 will regulate allo-immune responses. MHC: Major histocompatibility complex; TCR: T cell receptor; CD: Cluster of differentiation; DEC: Dendritic and epithelial cells; APCs: Antigen-presenting cells; UV: Ultraviolet; DC: Dendritic cell; LC: Langerhans cell; IL: Interleukin; NKT: Natural killer T.