Nasal epithelium forms the initial barrier between the environment and the respiratory system and may be a potential source of proinflammatory interleukins, which contribute to the pathophysiology of allergic and nonallergic rhinitis. To explore this possibility, epithelium and cultured human nasal epithelial cells from nasal turbinates of patients undergoing surgery for treatment of upper airway obstruction were examined for the spontaneous expression of interleukin (IL)-1 alpha, IL-1 beta, IL-6, and IL-8. Human nasal epithelial cell lysates and culture supernatants were assayed by two-site ELISAs specific for IL-1 alpha, IL-1 beta, IL-6, or IL-8. Maximum concentrations of these cytokines in supernatants ranged from approximately 0.2 to 2 ng/ml for IL-1 alpha, 1.5 to 7 ng/ml for IL-6, and 100 to 3000 ng/ml for IL-8. IL-1 alpha was predominantly cell-associated, whereas most of the IL-8 and all of the IL-6 were detected in the supernatant. Little or no IL-1 beta was detected by ELISA in the supernatants or cell lysates. Whole tissue turbinates and isolated epithelium were also examined for IL-1 beta, IL-6, and IL-8 mRNA expression by Northern blot analysis. IL-6 and IL-8 mRNAs were detected, whereas IL-1 beta mRNA was not. Furthermore, IL-6 and IL-8 release from human nasal epithelial cell cultures was enhanced by addition to the cultures of lipopolysaccharide, and IL-6 release was inhibited by polymyxin B. Thus human nasal epithelium may be a major source of IL-1 alpha, IL-6, and IL-8 in allergic and nonallergic rhinitis. Production of those proinflammatory cytokines by epithelial cells of the nasal and sinus mucosa may contribute to the pathologic and clinical events that occur in these diseases.