Circulating immune complexes in patients with atopic allergy

Summary Sera from forty‐nine patients with atopic allergy were tested for the presence of circulating immune complexes by the sensitive, quantitative Cl q assay. Compared to twenty‐five normal individuals the atopic patients had significantly higher mean values of Cl q reactive material, expressed as Cl q inhibition values. The highest mean values were seen in the group (twenty‐one patients) who had been on long term maintenance immunotherapy for 5 or more years. When positive sera were fractionated by ultracentrifugation on sucrose density gradients, the Cl q reactive material was found in intermediate (7S–19S) and heavy (>19S) regions. The heavy material contained both IgM and IgG. It is suggested that the IgG antibodies known to be produced by chronic hyposensitization procedures in allergic individuals may circulate in the serum as antibody–allergen immune complexes, and could carry out their blocking action in this form.