ELISA for Guinea-pig IgG1: An Alternative to the PCA Test for Relative Allergenicity

An ELISA method to replace the PCA (passive cutaneous anaphylaxis) test has been developed for use in the evaluation of relative allergenicity in guinea-pigs (Dunkin-Hartley). The method detects antigen-specific IgG1 antibodies formed in the guinea-pig during sensitisation, and correlates well with the corresponding PCA test. The relative importance of IgG1 and IgE for relative allergenicity in the Dunkin-Hartley guinea-pig strain is discussed.

An Investigation of the Allergens of Ascaris lumbricoides Using a Radioallergosorbent Test (Rast) and Sera of Naturally Infected Humans: Comparison With an Allergen for Mice Identified by a Passive Cutaneous Anaphylaxis Test

The identification of those components of Ascaris lumbricoides (var. suum) body fluid (ABF) which are IgE-inducing antigens (allergens) was found to depend on the type of assay used. By use of the radioallergosorbent test and sera from humans naturally infected with A. lumbricoides, it was found that ABF contains a range of allergens with a variety of isoelectric points and molecular weights. Some cross-reactions were demonstrated between the allergens of A. lumbricoides and Toxocara canis. On the other hand, when a passive cutaneous anaphylaxis assay was used with sera from mice sensitized by nasal inhalation of ABF plus Bordetella pertussis vaccine, it was found that only one relatively pure fraction of ABF was involved. This consisted of some of the largest protein molecules in ABF: it had a molecular weight of approximately 360000 (subunits 140000 and 220000), an isoelectric region of 8�0-8�4, and was clearly very different from the allergens isolated from ABF by other workers.

THE ANTIGENIC LOCI OF INSULIN

Insulin exhibited some cross-reactivity with the isolated S-sulfo A- and B-chains in the passive cutaneous anaphylaxis test. The synthetic peptides A1–9, A10–21, and A1–21 gave a passive cutaneous anaphylactic reaction with guinea pig antiserum to natural A-chain, whereas high levels of A10–21 and A1–21 could also inhibit a subsequent insulin challenge from reacting with antiserum to insulin. The synthetic peptides B1–8, B9–30, B24–30, and B1–30 reacted with antiserum to natural B-chain but high levels of peptides (B2–8)2, B9–14, and (B17–23)2 were inactive. The symmetrical double peptide (B1–8)2 reacted with guinea pig antiserum to intact insulin as well as with antiserum to B-chain and certain sera from insulin-resistant diabetic patients. The results indicated that injection of ox insulin into guinea pigs caused production of anaphylactic antibodies mainly towards antigenic loci in the regions A10–21 and B1–8 of the insulin molecule, whereas antigenic determinants in the regions A1–9 and B24–30 were less important.

MILK ALLERGY

The examination of sera from milk allergic children, children allergic to substances other than milk, and normal children, revealed no significant differences relative to coated tanned cell hemagglutinin titer or the presence of precipitating antibody as measured by gel diffusion for milk components. The passive cutaneous anaphylaxis test revealed a high percentage of positive responses with sera from milk allergic individuals only. The presence of milk hemagglutinins could not be demonstrated in the cord sera from 30 newborns. The results of this study suggest that the passive cutaneous anaphylaxis technique deserves further evaluation as a laboratory method for the confirmation of milk allergy.