Therapeutic effect and titers of the specific IgE and IgG antibodies in patients with sea squirt allergy (Hoya asthma) under a long-term hyposensitization with three sea squirt antigens.

Hyposensitization therapy with each of three sea squirt antigens, Gi-rep (molecular weight [MW] 106,000), Ei-M (MW 22,800), and DIIIa (MW 9980), have succeeded in 72%, 90%, and 36% of patients with sea squirt allergy, respectively, within the first year, and the effect has been maintained during subsequent 4-year maintenance therapy. All available sera from some of the hyposensitized patients were also examined for IgE and IgG titers against the most effective therapeutic antigen, Ei-M, and it was revealed that the Ei-M-specific IgG titer increased rapidly in the successfully hyposensitized patients, regardless of the therapeutic antigen used, except for a few patients. Furthermore, the high specific IgG titer, as well as the therapeutic effect, was maintained during the subsequent maintenance therapy. No such increase in the specific IgG titer was detected in all unsuccessfully hyposensitized patients. In contrast, the Ei-M-specific IgE titer was practically unchanged in all allergic patients, independent of the therapy. Therefore, the effect of the hyposensitization therapy was closely dependent on the induction of the specific IgG capable of competing with the specific IgE for a certain asthma-inducing antigen, like DIIIa. The apparently low therapeutic efficiency of DIIIa was attributed to its relatively low immunogenicity to induce the specific IgG.