Journal of Applied Physiology, Vol 58, Issue 2 485-491, Copyright © 1985 by American Physiological Society
Antigen sensitization and methacholine responses in dogs with hyperreactive airways
C. A. Hirshman and H. Downes
Antigen sensitization was induced in six Basenji-Greyhound (BG) dogs by
weekly aerosol exposure to Ascaris suum. The effects on airway
responsiveness to inhaled methacholine were studied before and at least 2
wk following Ascaris sensitization. All dogs developed detectable serum
levels of Ascaris-specific immunoglobulin E (IgE), and five out of six dogs
developed airway responsiveness to antigen over the 4- to 6-mo period. This
was accompanied by a decrease rather than an increase in airway
responsiveness to inhaled methacholine. When dogs were challenged with
methacholine 30 min after Ascaris antigen aerosol challenge, however, dogs
reactive to Ascaris became hyperresponsive to methacholine. The magnitude
of the response to antigen correlated (r = 0.85) inversely with the dose of
methacholine increasing pulmonary resistance 200%. These data show that in
BG dogs airway responsiveness to methacholine is increased by acute antigen
exposure but that sensitization of previously unsensitized dogs does not
increase nonspecific airway responsiveness.
