IgG4 antibodies in patients with atopic dermatitis.

The role of IgG4 in atopic dermatitis was investigated by determining the total amounts of IgG4 and of IgG4 specific for ovalbumin (a food allergen), Dermatophagoides farinae mite antigen and house dust (inhalant allergens) and Candida. These were related to the amounts of total and antigen specific IgE in patients with atopic dermatitis and normal healthy controls. Most patients with atopic dermatitis had greater amounts of total IgG4 and of antigen-specific IgG4 than did normal control individuals. Patients who had received hyposensitization treatment injections had greater amounts of IgG4 than the atopic dermatitis patients not so treated. In patients treated by hyposensitization there was a large increase in the amount of blocking antibody detected by incubating the antigen with the serum overnight before injecting the mixture into the skin of a patient sensitive to the antigen. Blocking activity was also examined by partial inhibition by the serum of IgE-mediated mast cell degranulation and by injection of serum into the skin of sensitive patients before challenge with antigens. In all tests the blocking activity of the serum was related to the amount of antigen-specific IgG4 but not related to total IgG4. In patients with atopic dermatitis who were sensitive to mite antigen, severe cases had small amounts of specific IgG4 and large amounts of specific IgE but in mild cases there was an opposite trend with relatively large amounts of specific IgG4. Large amounts of IgG4 ovalbumin specific antibody were found in children and adults with atopic dermatitis and egg allergy but small amounts of IgE. In infants most of the anti-ovalbumin antibody was IgE with little or no IgG4. The work of others has confirmed that increased amounts of total and antigen-specific IgG4 occur in atopic dermatitis, and it is concluded that IgG4 is a blocking antibody for anaphylactic sensitization responses.