IgE responses of malnourished mice: immunogenic and tolerogenic effects of low-grade antigenic stimulation

Effect of body mass on exercise-induced bronchospasm and atopy in African children

BACKGROUND

Sensitization to allergen is common in rural populations in less affluent countries, but atopic disease is less frequent than in richer countries. Variables explaining this dichotomy may provide insight into underlying mechanisms of atopic diseases like asthma.

OBJECTIVE

To test whether risk of exercise-induced bronchospasm (EIB) in urbanized African populations is increased in association with greater skin sensitivity or increased body mass.

METHODS

A total of 3322 children were enrolled in a prevalence survey of EIB in urban and rural South Africa. Children responding positively to an exercise challenge and a random sample of children responding negatively were recruited into a case-control study (393 controls, 380 cases). Subjects were investigated by using allergen skin prick testing, anthropometry, and assay of IgE. Stools were analyzed for parasite infestation.

RESULTS

The prevalence of EIB was higher in urban (14.9%) than rural (8.9%) areas (P < .0001). The difference in risk of EIB between urban and rural subjects was associated with atopy (odds ratio [OR] for upper tertile of skin wheal diameter, 2.65; 95% CI, 1.43-4.89; P < .0001), increasing weight (OR for upper tertile of body mass index [BMI], 2.17; 95% CI, 1.45-3.26; P = .001), and affluence. Increasing BMI was also associated with a greater strength of association between specific IgE and the corresponding skin test (Dermatophagoides pteronyssinus, OR for a positive skin test result in presence of specific IgE: heavier subjects, OR, 34.6; 95% CI, 0.9-109.3; P < .0001; lighter subjects, OR, 8.05; 95% CI, 2.74-23.6; P < .001).

CONCLUSION

Increases in BMI of rural children in subsistence economies may lead to an increased prevalence of atopic disease. This observation merits further investigation in prospective studies.

Effect of lifestyle on levels of specific IgE antibodies

Specific IgE antibodies against cobalt-conjugated human serum albumin (Co-HSA) were determined in serum samples from 706 hard metal workers who responded to a questionnaire on 17 physical and mental health practices. Hard metal (an alloy of cobalt) exposure resulted in significant (P < 0.05) increases in Co-HSA RAST indices in male subjects. In contrast, no factor concerning health practices made an independent contribution to elevation or suppression of specific IgE levels against cobalt. Although total IgE level was found to be significantly (P < 0.01) modulated by the cumulative health practice index (HPIA: Health Practice Index in Allergic reaction), which was extracted by MANOVA analysis while controlling for sex, age, and environmental factors, no significant association was found between HPIA and specific IgE level against cobalt. Multiple logistic analysis also revealed that health practices and hard metal exposure had a significant relative risk (> 2.3; P < 0.05) of elevating Co-HSA RAST index when the total IgE level was more than 400 IU/ml. Thus, a healthy lifestyle as well as discouragement of occupational exposure may be of benefit in reducing allergic disorders for persons with high IgE levels.