PARTIAL CHARACTERIZATION OF THE SILK ALLERGENS IN MULBERRY SILK EXTRACT

Although there have been reports of allergic reactions such as asthma and hypersensitivity pneumonitis to silk allergens (especially in orie ntal countries), these allergens have not been characterized We report an in vivo and in vitro study of subjects allergic to silk, as well a s a partial characterization of the allergens involved. Forty-one subj ects with a clinical history of silk allergy who had asthma, allergic rhinitis or both, and who had a positive intradermal skin test to mulb erry silk extract, were evaluated in the study. Four asthmatic subject s with negative skin tests and RASTs to mulberry silk extract were use d as controls. RAST specific IgE was present in 37/41 (90%) subjects. SDS-PAGE of mulberry silk extract demonstrated 13 protein bands of les s than 21-95 kD. IgE which bound io protein bands was present in 13/32 (41%) sera, twelve of which bound to a single protein with a molecula r weight between 35.1 and 59 kD. A pool made with the four control ser a did not react with any protein band. The patients allergic to silk s howed evidence of sensitivity to mulberry silk extract, both in vivo a nd in vitro, but sera from 19/32 (59%) subjects did not have antibodie s reactive with the mulberry silk extract immunoblot protein bands. Th e low avidity of the IgE may be responsible for this discrepancy betwe en in vivo and in vitro results.