A liquid-phase,
antigen-binding radioimmunoassay measuring subclass
IgG4 antibody (ab) to
allergens has been developed. This assay, which uses monoclonal anti-IgG4 to bind
IgG4, allows direct comparison of class (
IgG)- and subclass (IgG4)-specific ab levels. These assays used radiolabeled purified
allergens,
Der p I (Ag P1) from the dust mite Dermatophagoides pteronyssinus, Lol p I (Rye 1), from ryegrass pollen, hen's egg
ovalbumin, and
beta-lactoglobulin from cow's milk. We have investigated
IgG4 abs in several clinical situations. The results confirm that
IgG ab responses to both inhalants and food
proteins unequivocally include
IgG4 ab. On average, the proportion of
IgG4 ab to these
antigens is far higher than the contribution of
IgG4 to total
IgG. In patients with adult
atopic dermatitis, levels of both class and subclass ab were higher than in control subjects; however, the ratio of
IgG4:
IgG varied widely in patients and control subjects. During desensitization treatment of patients with perennial
rhinitis, levels of
IgG4 ab to
Der p 1 increased sharply, but there were also increases in the total
IgG ab responses so that the percentage contribution of
IgG4 was only moderately increased (mean values: before, 29%; after, 36%). In a prospective study of children from atopic families,
IgG4 abs to food
proteins were detectable as early as 3 months.
IgG abs to hen's egg
ovalbumin and
beta-lactoglobulin from cow's milk increased to a maximum at 3 years and declined by 5 years. However, specific
IgG4 as a percentage of specific
IgG increased progressively from a mean value of approximately 15% at 6 months to approximately 50% at 5 years of age.(ABSTRACT TRUNCATED AT 250 WORDS)