Interleukin-19 upregulates keratinocyte growth factor and is associated with psoriasis

Summary Background Interleukin (IL)-19, a member of the IL-10 family, signals through the IL-20R1 ⁄IL-20R2 heterodimer, which is shown to be involved in abnormal keratinocyte differentiation and proliferation. Little is known about its in vitro biological functions or its role in psoriasis. Objectives To investigate the role of IL-19 in the psoriatic process. Methods The expression of keratinocyte growth factor (KGF) transcripts was measured by polymerase chain reaction in CD8+ T cells treated with IL-19. Next, we developed monoclonal and polyclonal antibodies to measure the levels of IL-19 in the sera of patients with psoriasis and healthy volunteers using an enzymelinked immunosorbent assay. In addition, we performed immunohistochemical staining on psoriatic skin and normal controls. Results We found that IL-19 upregulated KGF transcripts on CD8+ T cells. Patients with psoriasis had a lower level of IL-19 in serum than healthy volunteers. The difference between these two groups was statistically significant ( P< 0AE05). IL-19 expression was seen in basal and suprabasal keratinocytes in a continuous pattern, and was increased in psoriatic epidermis. Conclusions These results suggest that IL-19 plays a role in the complex pathological cytokine network in psoriasis.