Functional dysregulation of dendritic cells in patients with papular urticaria caused by fleabite.

BACKGROUND Papular urticaria is a chronic allergic disease caused by fleabite. The presence of eosinophils, predominance of CD4-positive T cells in lesions, and IgE response suggest a Th2 immune response to flea proteins in patients with papular urticaria caused by fleabite (PUFB). Although PUFB is defined as an allergic reaction, the immunological mechanisms and the role of dendritic cells (DCs) have not been established. OBSERVATIONS Flea body extract did not induce the maturation of monocyte-derived DCs in 10 patients with PUFB and in 10 healthy children. Simultaneous exposure of DCs to flea extract and lipopolysaccharide induced increased expression of CD83 (P < .01), CD86 (P < .01), and HLA-DR (P < .05), which was statistically significantly greater in patients' cells. Dendritic cells from patients stimulated with lipopolysaccharide secreted less interleukin 6 (IL-6) and IL-10 than DCs from control subjects. CONCLUSIONS Results of this study indicate that the involvement of DCs in an immune response produced in the disease is mediated through the altered expression of membrane molecules. This may be related to constitutive impairment in the production of regulatory cytokines such as IL-6 and IL-10 in these patients.