The asthma syndrome: inciters, inducers, and host characteristics.

Abstract

The asthma syndrome: inciters, inducers, and host characteristics A number of prevailing assumptions about asthma would benefit from re-examination.An example is the view that the host abnormality in asthma is hereditary.Others include the concepts that the abnormality is stable and life-long, the measurement of a normal level of non-specific bronchial respon- siveness precludes the possibility of asthma in the individual, and asthma is an entity which is separate and distinct from others such as bronchitis, cystic fibrosis, and pertussis.The position which will be developed here is that these assumptions can now be taken as oversimplifications and, as such, at least partially in error.Numerous new insights into asthma have emerged from observations of responses to experimental inhalation challenges and observations of the effects of environmental exposures particularly in occu- pational settings.One type of challenge is the experimental allergen inhalation challenge test in allergic asthmatic individuals-this elicits two basic types of responses, the early (immediate) asthmatic response and the late (non-immediate) asthmatic response.Both may occur in the same individual in the so-called dual asthmatic response.'These responses are mimicked by responses to non-allergic stimuli including airborne chemicals encountered in the workplace.Some theoretical and practical implications of the patterns of responses to various stimuli will be considered here. IncitersEarly asthmatic responses develop within minutes of the stimulus and disappear in the first hour or so.The antigen-induced early asthmatic response results from the interaction of antigen with IgE antibody and subsequent release of mediators including histamine and SRS-A which appear to mediate the bronchoconstriction.23 Short-latency IgG antibody may replace the IgE antibody in some cases.4 5 Early responses also result from inhaled histamine,6 inhaled methacholine,7 inhaled cold air,8 hyperventilation,9 and exercise.'0The latter three stimuli apparently operate through heat exchange

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Affiliated Institutions

• Health Sciences Centre CA
• McMaster University Medical Centre CA

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