Robert G. Townley

Standardization of bronchial inhalation challenge procedures

A group of investigators interested in the standardization of inhalation challenge techniques was selected by the program directors of the Asthma and Allergic Disease Centers (AADC). This effort has been assisted by the National Institute of Allergic and Infectious Diseases of the National Institutes of Health. At the last meeting of the panel on February 15, 19’75, criteria for procedures and materials used were suggested in order to standardize bronchial inhalation challenges as they pertain to allergic disease.

Genetic analysis of allergic disease in twins

One hundred seven pairs of twins, sixty-one MZT and forty-six DZT, were investigated for allergic disease by a questionnaire, reaginic antibody levels, bronchial reactivity to inhaled methacholine, and skin test responses. Intrapair correlation coefficients (ri) of measured clinical markers of atopy were determined and a heritability analysis was performed. The intrapair correlation coefficient for serum IgE was 0.82 for MZT and 0.52 for DZT. The methacholine area demonstrated greater correlation in MZT with an ri of 0.67 compared to 0.34 for DZT. The total ISTS had an intrapair correlation coefficient of 0.82 in MZT and 0.46 in DZT. Our analysis demonstrates that methacholine sensitivity, total serum IgE levels, and total skin test scores to be heritable traits and suggests a genetic contribution to their expression.

The effect of age on methacholine response

Bronchial reactivity to inhaled methacholine exists in subjects with asthma but may occur in subjects with allergic rhinitis, chronic lung diseases, and during respiratory infections. In the absence of these factors, we found that age also has a significant effect on the methacholine response. One hundred forty-eight subjects, 5 to 76 years of age, were studied as normal control subjects in a natural history of asthma study. The methacholine response was measured by standard techniques. The analysis demonstrated that age had a significant effect on the methacholine response. In addition to known factors influencing the results of methacholine inhalation, young and older subjects may exhibit bronchial responses that may falsely suggest hyperreactive airway disease.

Specificity and sensitivity of methacholine inhalation challenge in normal and asthmatic children

The provocative dose of inhaled methacholine required to cause a 20% drop in the forced expiratory volume in 1 sec was evaluated in two selected pediatric populations. On the basis of a standardized respiratory questionnaire, 165 individuals 5 to 21 yr of age were identified. Included were 110 normal nonatopic individuals and 55 current asthmatic subjects. Methacholine inhalation challenges were performed by use of a standard inhalation procedure. Fifty-four (98.1%) of the asthmatic subjects responded to methacholine with a 20% drop in the forced expiratory volume in 1 sec. Seventy (63.1%) of the normal individuals did not respond to methacholine. The specificity and sensitivity of the methacholine challenge was best obtained at a provocative dose of 100 breath units of methacholine.

Methacholine inhalation challenge studies

Methacholine sensitivity has become a valuable and widely used technique for studying the irritability of the airways. Asthmatics are lOOto l,OOO-fold more sensitive than normal subjects to various mediators such as methacholine (P-acetyl methacholine).‘-” This degree of sensitivity has been used to define asthma and also as a genetic marker.l The methacholine responsiveness may be determined by 1 of 2 methods: (1) by determining dose-response curves to increasing concentrations of methacholine while keeping the number of breaths and the volume of methacholine inhaled constant” and (2) by determining dose-response curves by keeping the concentration constant while increasing the number of inhalations of methacholine.” The first method is currently being used more widely and has been recommended by the American Academy of Allergy to provide a standard and uniform method. It is described in detail elsewhere.” The second method has been used since 1962 and has been the basis for a number of short-term and long-term studies. We have recently compared both of these methods to determine the short-term reliability of each method. The dose-response curves and thus the degree of bronchial sensitivity were determined in 19 subjects in a randomized 4-way crossover study. Each subject was challenged twice by each method at 1-wk intervals. The short-term reproducibility for both methods was good (r = 0.934 and 0.942). The correlation between methods was also significant (r =0.953). The various pulmonary function parameters that can be evaluated during an inhalation challenge are numerous and include the FVC, FEV,, SG,,,, FEF,,-,,, PEFR, flow volume loops, etc. The easiest and the most widely used currently is the FEV,, which is the minimum requirement for comparison of responses as recommended by the Standardization Committee, j

Effect of hydrocortisone on beta-adrenergic receptors in lung membranes

Abstract It has been observed that glucocorticoids potentiate beta-adrenergic stimulation of cardiovascular and airway tissues. In order to investigate the mechanism of this potentiating action, we examined the effect of glucocorticoids on the number and affinity of beta-adrenergic receptors in animal lung tissues, by a direct binding technique using [125]I-Iodohydroxybenzylpindolol ([125]I-HYP), a potent beta-adrenergic receptor antagonist. Specific binding of [125]I-HYP to rat lung membranes was saturable with 386 fmol of [125]I-HYP/mg protein at saturation. The apparent equilibrium dissociation constant of [125]I-HYP for beta-receptors was 221 nM. Chronic administration of hydrocortisone increased the density of beta-adrenergic receptors by 70% from 386 fmol to 657 fmol/mg with some decrease in the affinity of [125]I-HYP for beta-adrenergic receptors. By contrast, adrenalectomy produced a 29% fall in the number of beta-adrenergic receptors without altering the affinity of [125]I-HYP for beta-receptors, and this change was reversed by exogenous adminstration of hydrocortisone. The present study suggests that glucocorticoids may participate in regulating the density of beta-adrenergic receptors, and may potentiate beta-adrenergic receptors stimulation, at least in part by increasing beta-receptor density in tissue membranes.

Segregation analysis of bronchial response to methacholine inhalation challenge in families with and without asthma

A segregation analysis was performed on the bronchial response to a standardized methacholine inhalation challenge obtained from members of 83 families that were part of a Natural History of Asthma study population. Each bronchial response was expressed as the area under the best fitting parabolic dose-response curve. Standard methods of statistical analysis demonstrated that age, sex, and recent respiratory infection had a significant effect on the bronchial response to methacholine inhalation. Segregation analysis indicated that, although a familial component exists in the transmission of bronchial response to methacholine, the bimodal distribution of the bronchial response is not due to segregation at a single autosomal locus.

Effects of platelet activating factor on the chemotaxis of normodense eosinophils from normal subjects

Highly purified eosinophils were obtained from normal subjects, and their chemotactic responses to platelet activating factor (PAF) were evaluated. PAF induced both eosinophil chemotactic and chemokinetic responses, and was 100 fold more potent eosinophil chemotactic factor as compared to eosinophil chemotactic factor of anaphylaxis. On the other hand, leukotriene B4 did not show any eosinophil chemotactic activity. A selective PAF antagonist, BN52021, inhibited eosinophil chemotaxis in a dose dependent manner. Preincubation of eosinophils with PAF induced the deactivation of eosinophils for further chemotactic responses to PAF. These findings suggest that PAF is a potent chemotactic factor for normal eosinophils.

The effect of beta adrenergic blockade on bronchial sensitivity to acetyl-beta-methacholine in normal and allergic rhinitis subjects.

The effect of propranolol inhalation on sensitivity to methacholine inhalation was studied in normal and allergic rhinitis subjects to determine whether beta adrenergic blockade alters sensitivity to mediators in nonasthmatic atopic individuals. A partial beta adrenergic blockade is suggested as being instrumental in asthma. Hay fever patients studied showed similar effects and also developed asthma for the first time.

Mycobacterial antigens attenuate late phase response, airway hyperresponsiveness, and bronchoalveolar lavage eosinophilia in a mouse model of bronchial asthma

Allergens, in combination with genetic predisposition, drive undifferentiated T cells towards the type 2 T cells. Some childhood infections may activate the production of a type 1 T cell profile. It is reasonable to speculate that a decrease in childhood infections may increase the incidence of allergy by allowing the immune balance to shift towards the type 2 T cells. We hypothesized that pre-exposure of mycobacterial antigens in sensitized mice would prevent the development of asthma-like conditions. Specifically, we examined the effect of mycobacterial antigens, Bacillus Calmette-Guerin (BCG) vaccine and Mycobacterium vaccae, on antigen-induced bronchoconstriction, airway hyperresponsiveness to methacholine, bronchoalveolar lavage eosinophilia, and plasma IL-4 and IL-12 levels in ovalbumin (OVA)-sensitized and challenged Balb/c mice. Challenge with OVA produced a 2-3-fold increase in bronchoconstriction within 3-5 min, followed by a delayed response after 60 min, the latter of which was significantly attenuated by both BCG and M. vaccae. Airway hyperresponsiveness to methacholine 24 h after OVA challenge was prevented by BCG and M. vaccae. Airway eosinophilia was also prevented by BCG and M. vaccae. The plasma IL-12 levels were significantly increased and plasma IL-4 levels were significantly decreased following BCG or M. vaccae administration in OVA-sensitized and challenged mice. Interestingly, a significant increase in plasma IL-12 was observed with BCG as compared to M. vaccae administration, suggesting a stronger type 1 response to BCG. These data support our hypothesis and suggest that BCG and M. vaccae may prevent the underlying pathophysiological changes in asthma.