DER-P-I, A MAJOR ALLERGEN OF THE HOUSE-DUST MITE, PROTEOLYTICALLY CLEAVES THE LOW-AFFINITY RECEPTOR FOR HUMAN IGE (CD23)

The nature of the proteases that cleave CD23 in vivo is of considerabl e interest, but remains unknown. Here, we demonstrate that Der p I, a major allergen of the house dust mite Dermatophagoides pteronyssinus, cleaves CD23 from the surface of cultured human B cells (RPMI 8866 B c ell line). The cleavage of the receptor from the B cell surface was as sociated with a parallel increase in soluble CD23 (sCD23) in the cultu re supernatant. Furthermore, the proteolytic effect of Der p I was spe cific for CD23, since none of the other B cell markers tested (CD20, H LA-DR, CD71 and CD49d) were affected. Labeled antibody experiments and protease inhibition assays clearly demonstrate that Der p I is a cyst eine protease that directly cleaves a 25-kDa fragment of CD23. These d ata suggest that the cysteine protease Der p I, in addition to being h ighly immunogenic, may up-regulate IgE synthesis by virtue of its abil ity to cleave CD23.