The present studies were conducted to determine whether different mediators are responsible for antigen-induced contraction of guinea pig lung parenchymal strips sensitized with either IgG or IgE. Passive sensitization was employed using IgG- or IgE-type antibody to ovalbumin which had been separated using Protein A-Sepharose as previously described (Regal, 1984a). Such a system ensures the presence of only one type of cytophilic antibody to mediate antigen-induced contraction of the isolated lung parenchymal strip. Pyrilamine, an H1 antagonist, caused a very slight delay in the onset of the antigen-induced contractions in both IgG- and IgE-sensitized strips, suggesting a very minor role for endogenous histamine in both systems. A combination of the leukotriene antagonists, FPL 55712, and pyrilamine caused a significant reduction in the antigen-induced contraction in IgE- but not IgE-sensitized lung parenchymal strips. Histamine release was detected on antigen challenge of both IgG- and IgE-sensitized lung. Using bioassay techniques leukotriene release was primarily detected from IgG-sensitized lung and only minimally from IgE-sensitized lung. Thus, our studies have demonstrated a differential antagonism of IgG- and IgE-mediated airway contraction and suggest that leukotrienes are important mediators of antigen-induced lung parenchymal contraction in IgG- but not IgE-sensitized tissues.
Bibliographical noteFunding Information:
The author would like to thank Ms. B. Elmquist and Ms. B. Sheedy for excellent technical assistance and Dr. Larry Thomas of Rush Medical College for performing the histamine analysis. This work was supported by NIH Grant HL28443.
- Guinea pig lung