Defined test reagents for the diagnosis of drug-induced allergy. Antibody-dependent skin reactions towards pyrazolinone and pyrazolidinedione derivatives in the guinea pig.

Chemically defined haptenic reagents and haptenic conjugates were synthesized for use in clinical skin testing. One series of reagents was based on the 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one structure, a second series on 1,2-diphenyl-pyrazolidine-3,5-dione. Haptens were connected via flexible spacer molecules which insert considerable distances between haptenic moieties and carriers. The skin test reagents were hexavalent conjugates prepared from the bis-penta-L-lysine carrier 'PAL'. The methodological details exemplify the application of N-hydroxysuccinimide activated ester derivatives for the preparation of peptidic conjugates. Rabbit and guinea-pig antisera against the haptens were obtained by immunization with human serum albumin conjugates. Efficacy and cross-reactivity relationships were assessed by guinea pig PCA and by testing actively immunized guinea pigs. A striking lack of cross-reactivity was found between pyrazolinone and pyrazolidinedione haptenic reagents in all test systems. On the other hand, the elicitation of homologous anaphylaxis was highly effective with the PAL conjugates. The data presented and discussed provide a basis for the evaluation of clinical tests performed in order to define drug-induced allergic reactions. They are relevant for immediate-type skin reactions as well as for serological methods.