Figure 4.

Histamine-pretreated dendritic cells (DCs) stimulate the recruitment of CD11c⁺ CD8 alpha⁺ DCs in the lungs of allergic mice and the production of Leukotriene B4 (LTB4). DCs pretreated or not with histamine and pulsed with ovalbumin (OVA) were intratracheally (i.t.) injected (5 × 10⁵ cells/allergized mouse), as described in the Materials and Methods. After 7 days, mice were killed and the lungs were processed. Lung cell suspensions were enriched in CD11c using antibodies directed to CD11c coupled to magnetic beads. Isolated cells were analysed for the expression of CD11c and CD8α, using specific antibodies labelled with phycoerythrin (PE) and fluorescein isothiocyanate (FITC), respectively. (a) Results are expressed as the percentage of cells double-positive for CD11c and CD8α [mean ± standard error of the mean (SEM); n = 6]. (b) A dot-plot of a representative experiment is shown. (c) CD11c⁺ cells purified from the lungs (1·5 × 10⁵ cells/200 μl) were cultured for 18 hr at 37° and the production of LTB4 was analysed in the supernatants by enzyme-linked immunosorbent assay (ELISA). Results are expressed in pg/ml, and represent the mean ± SEM of eight experiments. Asterisks indicate statistical significance (*P ≤ 0·01) versus controls (phosphate-buffered saline).