Isolation and Characterization of an Asthma-Inducing Sea-Squirt Antigen

An antigen capable of inducing asthmatic attack in patients with sea-squirt allergy has been isolated from body fluid of sea-squirt, Styela plicata, and designated as DIIIa. The chemical composition and the behavior in anion-exchange chromatography showed that the antigen was a weakly acidic glycoprotein. The weight-average molecular weight of DIIIa was estimated to be 9,880 by the sedimentation equilibrium method. This antigen was apparently discriminated from the previously isolated sea-squirt antigens, Gi-rep and Ei-M, by its activity to induce asthmatic attack and conjunctival congestion, though it gave a strongly positive reaction in skin tests against allergic patients, similarly to the previous antigens. From the cross-reaction of DIIIa to rabbit anti-Gi-rep and anti-Ei-M sera in vitro, it was confirmed that the antigen carried essentially the same antigenic determinant as Gi-rep and Ei-M, and this was termed type a determinant. Furthermore, the allergenic activities detectable in vivo and the reactivity to the rabbit antisera in vitro were simultaneously absorbed by immobilized immunoglobulin from anti-Gi-rep serum. Thus, it was suggested that the antigenic determinant responsible for the allergic reactions in vivo corresponded to that specified as type α in vitro on the basis of the reactivity against the rabbit anti-Gi-rep serum.