In vitro interleukin-5 production of peripheral blood mononuclear cells is increased in patients with asthma.

To determine whether the capacity of interleukin-5 (IL-5) production is increased in patients with asthma, we studied in vitro IL-5 production from peripheral blood mononuclear cells (PBMC) in 27 asthmatics (16 allergic asthmatics and 11 nonallergic asthmatics) and 10 normal subjects. IL-5 production of phytohemagglutinin (PHA)-stimulated PBMC was significantly greater in asthmatics than in normal subjects (p < 0.02). IL-5 production of PBMC by IL-2 stimulation was also significantly increased in asthmatics compared with that of normal subjects (p < 0.05). In contrast, IL-2 production of PHA-stimulated PBMC did not significantly differ between asthmatics and normal subjects. In addition, the number of CD4+ and CD8+ T cells in PBMC or CD4+/CD8+ ratio did not significantly differ between asthmatics and normal subjects, whereas CD25+ T cells were significantly increased in asthmatics compared with those of normal subjects (p < 0.02). Finally, there was no significant correlation between the in vitro IL-5 production of PBMC and blood eosinophil counts in asthmatics and normal subjects. Our results indicate that the capacity of IL-5 production, but not of IL-2 production, is increased in asthmatics. The increased capacity of IL-5 production might be involved in the migration and activation of eosinophils in the airways of asthmatics.