Priming with murine recombinant interleukin-5 resulted in the augmentation of PAF-induced airway hyperresponsiveness to histamine in guinea pigs.

The effects of pretreatment with murine recombinant interleukin 5 (mrIL-5) on platelet activating factor (PAF)-induced bronchoconstriction and airway hyperreactivity were investigated in guinea pigs. The intratracheal administration of mrIL-5 (2.5-10 micrograms) augmented platelet activating factor (PAF; 50 ng/kg)-induced bronchoconstriction in guinea pigs. When IL-5 (2.5 micrograms) was injected intratracheally, PAF (25 ng/kg)-induced bronchoconstriction was not affected, but PAF-induced airway hyperresponsiveness to histamine was exacerbated. Airway inflammation, in terms of increased capillary permeability and the accumulation of leukocytes in bronchoalveolar lavage fluid, was not produced by pretreatment with PAF (25 ng/kg), mrIL-5 (2.5 micrograms), or by a combination of these agents. This mrIL-5-induced augmentation of airway hyperreactivity by PAF was clearly inhibited by the phosphodiesterase-type III inhibitors, SDZ-MKS-492 and AH 21-132, but not by aminophylline.