THE ROLE OF IGG IN TYPE-I ALLERGY - AN UNSOLVED PROBLEM

The role of antiallergen IgG antibodies in allergy remains unclear In this review we present evidence for and against the hypothesis that Ig G (IgG(4)) could act as a sensitizing antibody. After considering the available data, we conclude that the possible sensitizing ability of I gG(4) may depend on the nature and origin of the antibodies and cells used in the Various experiments and/or is related to the differential induction of two subtypes of IgG(4) (anaphylactic vs. blocking). If st ill remains to be settled whether the observed increase in specific Ig G during immunotherapy is causally related to the relief of symptoms, or whether it merely represents an epiphenomenon due to high antigen e xposure. Furthermore, the presence of IgG anti-IgE antibodies in the s erum of allergic patients and their possible pathophysiological releva nce is discussed int the light of recent evidence suggesting that the raised levels of these antibodies may likewise represent an epiphenome non of the immune response. There exists a tight relationship between antiallergen IgE and IgG antibodies. This correlation has led to the s uggestion that IgG determinations might be useful far diagnostic purpo ses. There also exists a good correlation between these antiallergen i sotypes in inhibition assays, It has therefore been proposed to employ inhibition of IgG binding for the standardization of allergenic extra cts. More recent studies explore the relevance of the binding affiniti es or avidities of allergen-specific IgG antibodies. Antibody affinity may have important repercussions with respect to the biological effec ts. If has been pointed out that the affinity of specific IgG subclass es in allergic patients depends, among other things, on the nature of the sensitizing allergen. Further studies on IgG binding to the so-cal led ''major'' and ''minor'' allergens may help clarify the role of IgG in allergic disorders.