Structure-activity relationships in allergic contact dermatitis.

Skin sensitization by simple chemicals involves reaction with nucleophilic groups on skin proteins or possibly on proteins in cell membranes to form haptenic groups, which act as allergenic determinants. A quantitative model for sensitization by 'alkylating agents', the RAI (Relative Alkylation Index) theory, has been devised and applied to the sensitization observed with three model series of compounds--p-nitrobenzyl halides and saturated and unsaturated sultones. Examination of chemical structures, and predictions of the types of chemical reaction that substances may undergo, can be used to assess the likely reactivity of unknown materials towards skin proteins. In addition such examinations of structure may be used to assess the likely cross-reactivity of materials. The pro-hapten concept of Dupuis & Benezra (Allergic Contact Dermatitis to Simple Chemicals. A Molecular Approach. Marcel Dekker, New York) offers an explanation for the sensitization potential of substances that do not contain chemically reactive groups prior to in vivo conversion and for cross-reactions between apparently unrelated chemicals.

Correlations between skin sensitization potential and chemical reactivity for p-nitrobenzyl compounds.

Quantitative relationships between skin sensitization potential and certain physico-chemical properties of alkylating agents have been reported. This study demonstrates the correlation of the relative alkylation index (RAI), derived from the alkylation rate and lipophilicity of an alkylating agent, with a set of experimental sensitization data obtained for a series of p-nitrobenzyl compounds.

IgE antibody levels to ingested soya protein determined in a normal adult population.

Levels of soy protein-specific IgE were measured in a normal adult population (seventy-four males, and fifteen females) who ingested soya-containing and control diets during two 4-week periods. Increases in soya-specific IgE were observed for some individuals following ingestion of the soya-containing diet, and for the female group the increase in soya-specific IgE was statistically significant (P = 0.02). The increase of soya-specific IgE was small and led to lower levels than that associated with adverse effects. The increase in soya-specific IgE in the female group was accompanied by a significant increase (P = 0.02) in total immunoglobulin A. Changes in the level of soy-specific haemagglutinating antibody, soya-specific IgG, IgA and IgM as measured by ELISA and the immunoconglutinin titre could not be related to ingestion of the soya-containing diet.

Influence of detergent washing powders on minimal eliciting patch test concentrations of nickel and chromium.

Minimum eliciting levels of nickel have been estimated in 25 nickel-sensitive subjects, and of chromium in 14 chromium-sensitive subjects by patch tests with aqueous solutions of the respective metals. The minimum level of each metal required to provoke a patch test reaction was considerably greater than that found in fabric washing powder solutions and was in the majority of patients tested of the order of 112 ppm nickel (0.05% nickel sulphate) or 885 ppm hexavalent chromium (0.25% potassium dichromate). One nickel-sensitive subject and one chromium-sensitive subject reacted to 1 ppm of the respective metal. Fabric washing powder did not significantly alter the patch test reaction to nickel sulphate or provoke reactions in nickel- or chromium-sensitive subjects. EDTA significantly reduced the number and severity of patch test reactions to nickel sulphate but not those to potassium dichromate or trivalent chromium.

Immunological studies on tartrazine and its metabolites. I. Animal studies.

Tartrazine is occasionally associated with some clinical changes which have been attributed to allergy. In tests on laboratory animals with tartrazine and its metabolites by methods which should have detected potential to induce antibody formation, no antibodies were detected except by methods which are artificial in terms of human exposure. Similarly, laboratory methods have shown that the metabolites of tartrazine, and in some cases tartrazine itself, can induce contact sensitization in guinea pigs, although there is little evidence that tartrazine can induce similar changes in man.

RAST using crude and purified anti-IgE.

The sensitivity of the RAST using anti-IgE in 125I-labelled IgG fractions of sheep antiserum was compared to that using anti-IgE purified by immunosorbent techniques in tests with three allergens (grass pollens, Aspergillus fumigatus and the detergent enzyme "Alcalase") on sera from 248 workers in a detergent factory. Both anti-IgE reagents measure the same antibody but the RAST procedure using the crude anti-IgE reagent is less sensitive than that using the immunosorbent-purified anti-IgE in its ability to detect circulating IgE in subjects with positive skin-prick tests. In general the agreement between positive RAST and positive skin test was improved when only skin tests equal to or greater than 3 mm were considered positive. With Alcalase, antigen non-specific binding by the crude anti-IgE reagent may give false positive results. Optimal conditions for the preparation of allergosorbents with this allergen are defined. Predictive equations relating the results of RAST and skin test show that the hitherto arbitrary definition of a positive RAST result is statistically valid.

Investigation of the prohapten concept. Cross reactions between 1,4-substituted benzene derivatives in the guinea pig.

It has been proposed that the cross-reactions seen clinically between hydroquinone and para-phenylenediamine (PPD) arise from the formation of a common hapten, benzoquinone, in vivo, and that these chemicals therefore represent "prohaptens". A series of 1,4-substituted benzene derivatives has been used to examine this prohapten concept in the guinea pig model. Using both topical and intradermal routes of application, it is demonstrated that in the guinea pig 1,4-substituted benzene derivatives capable of oxidation to benzoquinone, including hydroquinone and PPD, show only restricted evidence of cross-reactions. These results support the prohapten concept. However taken in combination with data on cross-reactivity with 1,2- and 1,3-substituted benzenes, rather than giving rise to a single common hapten, they can be more readily interpreted as the formation of a spectrum of antigenic determinants in vivo, some of which are shared in common.

The effect of tartrazine on histamine release from rat peritoneal mast cells.

The release of histamine from purified rat peritoneal mast cells induced by specific antigen (egg albumin), compound 48/80 and calcium ionophore A23187 was modified by tartrazine. Histamine release induced by 48/80 and antigen was inhibited by the presence of 10(-5) to 10(-2)M tartrazine. The inhibitory effect on egg albumin induced histamine release was maximal when the tartrazine was added simultaneously with egg albumin, and was reduced by increased preincubation of the cells with tartrazine. Tartrazine had a small inhibitory effect on ionophore induced release at high concentrations, but augmented histamine release at tartrazine concentrations of 10(-3) and 10(-4)M. Augmentation of ionophore induced release was maximal at between 0-5 min preincubation of the cells with tartrazine.

A comparison of three guinea-pig sensitization procedures for the detection of 19 reported human contact sensitizers.

A maximization test (after Magnusson & Kligman 1970), a single injection adjuvant test (SIAT) and a modified Draize test procedure for assessing contact sensitization potential in guinea-pigs have been compared for their ability to detect 19 known human contact sensitizers. The results show that the modified Draize procedure is a good screening test particularly for strong sensitizers. The maximization procedure is a very stringent test of sensitization potential, able to detect some marginal sensitizers. The sensitivity of the SIAT procedure is sufficiently similar to that of the maximization test to act as an alternative for routine testing, particularly in view of its practical advantages over the maximization procedure.

Induction of photoallergy in guinea-pigs by injection of photoallergen-protein conjugates.

Photoconjugates were prepared by ultraviolet irradiation of guinea-pig albumin (GPA) with the photoallergens tetrachlorosalicylanilide (T4CS) and fentichlor. Injections of T4CS-GPA induced photoallergy to T4CS in 11 of 12 guinea-pigs whereas injections of fentichlor-GPA induced photoallergy in 5 of 12 guinea-pigs. Thus the fentichlor-GPA photoconjugate, which contained a molar ratio of hapten to protein 3 times higher than the corresponding T4CS conjugate, produced a significantly lower response. The results demonstrate the importance of protein conjugate formation in the induction of photoallergy, i.e. the role of carrier protein in contact sensitivity. The high potency of the T4CS-GPA photoconjugate in inducing photoallergy suggests that albumin may have a special role as a carrier protein in T4CS photoallergy.

Methyl groups as antigenic determinants in skin sensitisation.

The methylating agents, methyl dodecane sulphonate, methyl hexadecane sulphonate and methyl hexadec-3-ene sulphonate are strong skin sensitisers, cross-reactive with one another, in guinea pig adjuvant tests. Differences in potency are observed among these 3 compounds, and the possible reasons for this are discussed. Isoeugenol fails to elicit a sensitisation response when challenged onto guinea pigs sensitised to methyl dodecane sulphonate, indicating that the mechanism of isoeugenol sensitisation is not based on methyl transfer. It is proposed that, in skin sensitisation involving small haptenic groups, antigenic specificity is directed not against the haptenic groups but against portions of the carrier protein whose configuration has been modified as a result of the carrier-hapten reaction. This concept is supported by published data on cross-reactivity patterns with enantiomeric pairs of alpha-methylene-gamma-butyrolactone derivatives.

IgE antibodies to food allergens detected by ELISA, RAST and monkey PCA.

IgE antibody to twelve common food and inhalant allergens was measured by enzyme-linked immunosorbent assay (ELISA) in the sera of thirteen atopic patients with one or more allergic disorders (asthma occurring in eleven; rhinitis in ten; eczema in six; urticaria in four; mouth and gastro-intestinal symptoms in six), of twelve non-atopic patients with various clinical symptoms (asthma in four; rhinitis in four; eczema in one; urticaria in two; mouth and gastro-intestinal symptoms in four) and sixteen cord blood sera. The atopic patients had significantly higher IgE ELISA values to the twelve allergens tested than non-atopic persons (P less than 0.01) and cord blood sera (P less than 0.001). Further investigation of IgE antibody to egg white in a group of twenty-two maternal-infant-paired sera using RAST and ELISA techniques showed two cord blood sera that had reproducible RAST values significantly greater than the mean of the maternal group. This was confirmed by RAST inhibition studies but not by monkey PCA tests. High IgE ELISA values to egg white extract did not correlate with RAST results.

Immediate contact reactions to chemicals in the fragrance mix and a study of the quenching action of eugenol.

In this study, the nature of non-immune immediate contact reactions (NIICR) produced by cinnamic aldehyde, benzoic acid and sorbic acid were investigated, with particular interest in the 'quenching' ability of eugenol. Three groups of human subjects were studied, and the guinea-pig ear was also used as a model of NIICR. Cinnamic aldehyde, benzoic acid and sorbic acid were all able to produce NIICR in the majority of subjects studied. There was a strong correlation between the susceptibility of each subject to each urticant, but no correlation between the susceptibility to NIICR and age, atopic status or tanning ability. Eugenol caused a reduction in NIICR induced by all three urticants. This 'quenching' effect was apparent even when the eugenol was applied up to 60 min prior to application of cinnamic aldehyde, and its effect was not eliminated by washing. In the guinea-pig-ear model, ear thickening was induced by all three urticants, and this response was inhibited by eugenol.

High-fat diets and the immune response of C57Bl mice.

As a basis for studies of the influence of lipids on the immune response and health, adult C57Bl mice were fed for 10 weeks or longer on one of the following diets: high (200 g/kg) polyunsaturated fatty acid, high (200 g/kg) saturated fatty acid and low (50 g/kg) polyunsaturated fatty acid purified diets and a standard commercial diet. The three test-fat diets were compounded to have approximately the same energy content and the mice of each group maintained similar body-weights. High-fat diets significantly reduced their subsequent delayed hypersensitivity response to challenge after sensitization with tuberculin. Immunoglobulin IgM antibody formation against Escherichia coli lipopolysaccharide was transiently decreased, but IgG antibody against sheep erythrocytes and killed salmonella vaccine, IgG and IgE antibodies against ovalbumin remained unaffected. Total and differential blood counts revealed no differences between mice on high-fat and control diets in either the absolute numbers or the proportions of the types of leukocytes. Studies on peritoneal macrophages from mice of each group showed no difference in morphology and they ingested non-toxic and toxic particles releasing similar amounts of lactate dehydrogenase (EC 1.1.1.27) and beta-glucuronidase (EC 3.2.1.31) for each substance, indicating that there were no differences in viability or phagocytic function. The present study shows that the C57 Bl mouse can provide a model for the investigation of some consequence of the reduced immunocompetence induced by high-fat diets.