Stimulation by specific allergens induces inflammatory cytokine production from peripheral blood mononuclear cells (PBMCs) in patients with atopic asthma, but the mechanism remains unknown. PBMCs were collected from six patients with atopic asthma with an immunoglobulin E-radioallergosorbent test score to Dermatophagoides farinae of > or = 4 and six nonatopic healthy subjects (score = 0) using a dish adhesion method after density gradient centrifugation. CD23 expression in PBMCs was analyzed by the fluorescence-activated cell sorting method. PBMCs were incubated with D. farinae or lipopolysaccharide, and production of tumor necrosis factor (TNF) alpha into the supernatant was measured by enzyme-linked immunosorbent assay. After incubation, immunostaining nostaining of the PBMCs with anti-nuclear factor kappa B (NF-kappa B) antibody (anti-p65 antibody against p65 as the subunit of NF-kappa B) was performed, and NF-kappa B activation in extracted nuclear protein was examined by electrophoretic mobility shift assay. CD23 expression was significantly higher in PBMCs from patients with asthma than in the controls (p < 0.01). There was no significant difference in TNF-alpha production by lipopolysaccharide stimulation between the two groups, but D. farinae-specific TNF-alpha production was significantly higher in subjects with asthma than in the controls (p < 0.05). A significant translocation of NF-kappa B to nuclei by D. farinae stimulation was observed in cells from subjects with asthma (p < 0.01). Our results indicated that TNF-alpha production was induced by D. farinae in PBMCs of patients with atopic asthma by the activation of NF-kappa B via CD23. In patients with atopic asthma, CD23-mediated signals may cause proinflammatory cytokine production, which may lead to airway inflammation.