Allergen-specific IgG-4 in patients with atopic diseases of the respiratory tract.

Serum levels of total IgE, allergen-specific IgE (asIgE) and allergen-specific IgG-4 (asIgG-4) were measured in 194 patients in whom atopic disease of respiratory tract was suspected. The patients were divided into 8 groups based on the results of skin testing and sera levels of IgE and asIgE. Increase of the serum asIgG-4 level was observed in only 26 cases (13%), and occurred exclusively in patients with positive skin reactions to allergen(s) accompanied by increased serum levels of asIgE. In contrast, no significant elevation of serum asIgG-4 was found in non-atopic patients and in patients in whom skin testing and serologic evaluation did not yield conclusive results. These results argue against involvement of asIgG-4 antibodies in the pathogenesis of atopic diseases and against their function as sensitizer of target cell, analogous to the function of asIgE. In the present study elevated level of serum asIgG-4 was noted predominantly in asthmatic patients previously subjected to specific desensitization, that is to repeated exposure to antigen (allergen), which could induce specific antibody response. It is in agreement with the notion, that the appearance of asIgG-4 antibodies in sera of the patients under study is a consequence of the specific immunization, and not of atopy.