Increased interleukin‐10 and macrophage inflammatoryprotein‐1α release from blood monocytes <i>ex vivo</i> duringlate‐phase response to allergen in asthma

We determined the effect of late-phase responses to allergen challenge of mildly allergic asthmatic patients on the expression and release of the cytokines IL-10 and MIP-1alpha from peripheral blood monocytes.Sixteen mildly allergic asthmatics were exposed to increasing concentrations of allergen aerosol. Nine demonstrated an early response alone (single responders), while seven had an early followed by a late response (dual responders). Monocytes were isolated from venous blood before and 24 h after allergen challenge, and placed in short-term culture for determination of IL-10 mRNA expression by reverse-transcription polymerase chain reaction and protein release. MIP-1alpha protein release was measured by radioimmunoassay.IL-10 mRNA expression was significantly higher in dual responders than early responders alone, for unstimulated monocytes or for monocytes exposed to lipopolysaccharide or IL-1beta. In addition, the release of IL-10 and MIP-1alpha from monocytes of dual responders was also enhanced.Circulating monocytes are primed to release more of the cytokines, IL-10 and MIP-1alpha, in dual but not in single responders, at 24 h after allergen. They may contribute to allergen-induced inflammatory responses in the airways.