Sulfadiazine sensitivity with demonstrable skin-sensitizing antibody in the serum

Detection of human IgE to sulfamethoxazole by skin testing with sulfamethoxazoyl-poly-L-tyrosine

Adverse reactions to sulfamethoxazole (SMX) occur in 4% to 6% of normal individuals. Many of these reactions resemble immunopathologic reactions, but skin test or in vitro evidence of a role for IgE is limited. Earlier RAST studies in our laboratory provided evidence that the N4-SMX hapten was a major determinant in immediate hypersensitivity reactions to SMX. We tested the hypothesis that IgE to this hapten is present on the mast cells of patients who have experienced immediate hypersensitivity reactions temporally related to exposure to SMX. A multivalent skin test reagent, SMX168-poly-L-tyrosine, and a univalent hapten, SMX-tyrosine, were synthesized. Forty-four patients with histories of allergic reactions to SMX and six subjects who had been exposed to the drug, but who had not reacted, were skin tested. Twenty-seven percent of the history-positive patients were skin test positive. None of the control individuals was positive. The immunologic responses to SMX in three patients who had experienced allergic reactions during SMX/trimethoprim therapy were analyzed in serial skin test and RAST assessments. One to three years after the clinical reactions, IgE to SMX could be demonstrated by skin testing in all three patients with a SMX-poly-L-tyrosine skin test reagent. Skin test reactions were inhibited by the monovalent reagent, SMX-tyrosine, in a dose-dependent manner. SMX-specific IgE antibodies could also be detected by RAST in serum obtained within days of the reactions from two of the three individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of human IgE to a sulfonamide determinant

We tested the hypothesis that patients who experience immediate hypersensitivity reactions to sulfonamides (SM) express IgE that can bind to a N4-sulfonamidoyl determinant (N4-SM). Sulfamethoxazole (SMX) was coupled to CNBr-activated cellulose disks to form a matrix predominantly substituted with isourea-linked N4-SMX determinants. After incubation of human sera with these disks or bovine serum albumin substituted disks as a control, the binding of IgE was assessed with 125I-labeled antihuman IgE. The binding ratios (counts per minute SMX disks per counts per minute bovine serum albumin disks) for sera from nonallergic donors and newborn infants averaged 1.11 (+/- 0.21 SD). Sera from 10 patients with histories of apparent immediate hypersensitivity reactions to SM were studied. Ratios greater than or equal to 2.1 (greater than 4 SD above control) were detected in 70% (seven of 10). Significant binding was detected in the sera of three of seven patients with other forms of SM allergy. Preincubation with SMX (80 mmol/L) inhibited binding 7% to 35% in eight of the 10 positive sera tested. Binding of one highly reactive serum was significantly inhibited by SMX, sulfamethizole, and sulfamerazine, but not sulfanilic acid or trimethoprim. The results of this study suggest that N4-SM is a major determinant recognized by IgE to SM and that an in vitro assay capable of detecting IgE to SM has been developed.