PURIFIED DER P1 AND P2 PATCH TESTS IN PATIENTS WITH ATOPIC-DERMATITIS- EVIDENCE FOR BOTH ALLERGENICITY AND PROTEOLYTIC IRRITANCY

Atopic dermatitis has many similarities with allergic contact dermatit is. Previous studies have revealed delayed-type allergic reactions ind icating specific cell-mediated immune reactions in subgroups of patien ts, It has recently been recognized that purified house dust mite majo r allergens, Der p1 and Der p2 from Dermatophagoides pteronyssinus, ex hibit a proteolytic enzyme activity similar to papain and maybe serine proteases (e,g. trypsin), respectively. This opens the possibility th at house dust mites apart from an allergic epitope could elicit irrita nt reactions in atopic skin. We examined cutaneous reactivity to the p urified proteins of house dust mite antigens, Der p1 and Der p2, in 36 consecutive patients with atopic dermatitis, We also patch-tested wit h trypsin and papain, in order to see if these proteolytic enzymes cou ld induce irritant reactions. Twelve patients had type 1 allergy to De r p1 and two of these had type TV reactivity to D, pteronyssinus extra ct. Positive reactions were observed in another four patients, but the y had also irritant reactions to papain and trypsin, indicating that t he enzymatic activity may have elicited the reactions. The cutaneous r eactivity was not linked to total serum IgE, but the patients with spe cific allergic patch tests had type I reactions to D, pteronyssinus ex tract. Our observations indicate that allergic patch tests towards Der p1 and p2 are rare and that irritant reactions from D.pteronyssinus p roteolytic activity may be a more common phenomenon when patch-testing atopic dermatitis patients with house dust mite antigen extract.