Rabbit F(ab')2 antihuman IgE is a universal skin test reagent in the evaluation of skin mast cell degranulation in vivo

Anti-IgE-induced accumulation of leukocytes, mediators, and albumin in skin chamber fluid from healthy and atopic subjects

The aim of this study was to examine potential differences between healthy and atopic subjects with regard to IgE-mediated cutaneous inflammation. For this purpose, we analyzed histamine, tryptase, leukotriene B4, albumin, eosinophils, and total leukocytes in skin chamber fluid after challenge with anti-human IgE. We also measured gross skin reactivity (wheal, flare, and late-phase reactions), circulating IgE, and eosinophils, as well as the state of eosinophil activation. It was found that despite having more circulating IgE, the skin responsiveness of the atopic subjects did not differ significantly from that of the nonatopic subjects with respect to mediator release, albumin extravasation, or total recruitment of leukocytes. Moreover, the sizes of anti-IgE-induced wheal, flare, and late-phase reactions were very similar in the two groups. On the other hand, significant recruitment of eosinophils during the IgE-mediated reaction was more or less restricted to the atopic group. Yet the recruited eosinophils, of which the majority was in an early state of activation before degranulation, did not seem to contribute significantly to the IgE-mediated delayed skin edema. Furthermore, the eosinophil count in anti-IgE chambers of the atopic subjects did not correlate with any of the other parameters monitored. Thus because the anti-IgE-induced recruitment of eosinophils appeared to be unrelated to factors such as the number of peripheral blood eosinophils, the degree of mast cell activation, the intensity of inflammatory skin changes, and the level of circulating IgE, it is apparent that the mechanisms for and pathophysiologic role of IgE-mediated dermal eosinophil accumulation in atopic subjects require further investigation.

Allergen-induced histamine release in intact human skin in vivo assessed by skin microdialysis technique: characterization of factors influencing histamine releasability

BACKGROUND

The purposes of the study were to characterize allergen-induced histamine release in intact human skin in vivo by using a novel microdialysis technique and to study covariates influencing histamine releasability.

METHODS

Hollow microdialysis fibers were inserted into the upper dermis in 15 timothy-sensitivity subjects. Up to 12 fibers were inserted in each subject. Each fiber was perfused with Krebs-Ringer's solution at a rate of 3.0 microliters/min. Three to four serial dilutions of allergen were applied to the skin by intracutaneous injections or skin prick test above individual fibers. Samples were collected in two 2-minute fractions before skin challenge and in 10 consecutive samples for 20 minutes after skin challenge. Histamine was assayed spectrofluorometrically.

RESULTS

A significant dose-response relationship for histamine release was demonstrated with intracutaneous tests and skin prick tests. The time to reach peak histamine release after an intracutaneous test was 4 to 8 minutes, compared with 12 to 14 minutes for a skin prick test. Histamine release correlated significantly with wheal size. Intrasubject coefficient of variation on histamine release was about 20%. A substantial intersubject variation in histamine releasability was observed. Seventy to seventy-five percent of the variation could be accounted for by a combination of gender, total and allergen-specific IgE, and an in vitro basophil histamine release test.

CONCLUSIONS

Using a skin microdialysis technique, we have described in detail histamine release in intact human skin by allergen. The microdialysis method proved to be a reproducible technique for monitoring histamine release in allergic skin reactions and for studying histamine releasability of skin mast cells in vivo.

The relationship between RAST and skin test results in patients with asthma or rhinitis: a quantitative study with purified major allergens

BACKGROUND

Study of the relationship between skin test results and IgE antibody levels is seriously hampered by the use of conventional allergen extracts because the precise amount of relevant allergen for each patient is unknown.

OBJECTIVE

This study was designed to investigate skin reactivity with purified major allergens and to assess the relation with serum levels of IgE antibodies and to determine which additional factors contribute to the skin test result.

METHODS

We used five purified major allergens (Der p 1, Der p 2, Fel d 1, Lol p 1, and Lol p 5) in skin tests, RASTs, and histamine release tests in 43 multisensitized patients with asthma or rhinitis.

RESULTS

The differences in biologic activity of the five major allergens at a given level of specific IgE are within one order of magnitude. A significant residual variation remains in the correlation between skin test results and levels of IgE antibodies, which cannot be explained by imprecision of both tests (Pearson log skin test vs log specific IgE: r = 0.46-0.92). With similar levels of specific IgE, the amount of allergen that is required for a positive skin test result may differ by as much as a factor of 100 between patients. The amount of total IgE in serum contributes significantly to the skin test result. High values of total IgE are accompanied by a lower skin reactivity for allergen. Within individuals, allergens that cause skin test results that deviate from the prediction based on IgE antibody level often show a similar deviation in the histamine release test. This indicates that the type of IgE response (i.e., affinity or epitope recognition pattern) contributes significantly to the skin test result. Skin reactivity for histamine does not significantly influence the skin reactions expressed as allergen threshold. However, increased skin reactions with higher allergen dosages depend on histamine reactivity.

CONCLUSION

The major allergens tested show similar biologic activities. In addition to IgE antibody level, total serum IgE and type of IgE antibody response contribute significantly to the skin test threshold for allergens. Even in a system with purified allergens, IgE antibody levels and skin test results are not interchangeable as an indicator of the degree of allergic sensitization.

Effects of loratadine on anti-IgE-induced inflammation, histamine release, and leukocyte recruitment in skin of atopics

The aim of this study was to assess the ability of the H1-receptor antagonist loratadine to modify anti-IgE-induced cutaneous wheal-and-flare and late-phase reactions (WFR and LPR), as well as histamine release and leukocyte accumulation in skin chambers. For this purpose, 10 atopics with allergic rhinitis were entered into a double-blind crossover study in which they received either placebo or loratadine (20 mg/day orally) for 8 days separated by a 7-day washout period. Blisters were induced on both forearms on day 7 of each treatment period, and were unroofed on day 8 and covered with plastic skin chambers. Chamber fluids were collected during 7 h after 1-h incubation with anti-IgE or control IgG. Intradermal challenge with histamine and anti-IgE was performed at the same occasion. As compared to placebo treatment, loratadine inhibited the immediate WFRs to anti-IgE by 35% (wheal) and 65% (flare), respectively (P < 0.01), and corresponding reactions to histamine challenge by 50% and 70% (P < 0.001), respectively. Moreover, the initial phase (0-2 h) of the LPR induced by anti-IgE was attenuated by up to approximately 60% (P < 0.001) during loratadine treatment. Thereafter, no inhibition of the LPR was observed. The magnitude and time course of histamine release into skin chambers was virtually the same after loratadine and placebo treatment, with a peak during 0-1 h and a progressive decline during the following 2 h. Accumulation of alpha 2-macroglobulin, reflecting extravasation of large plasma proteins, also peaked during the first hour and was unaffected by loratadine during the 8-h observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial immunological investigations in a patient who had a life-threatening reaction to intravenous protamine

Reactions to intravenous protamine include rash, urticaria, bronchospasm, hypotension, and/or pulmonary artery pressure elevation. We have previously shown that in diabetic patients receiving daily protamine-insulin injections, the presence of anti-protamine IgE or IgG antibodies are significant risk factors for acute, life-threatening reactions when protamine is given intravenously. To study protamine reactions further, we measured serum anti-protamine IgE and IgG antibody levels, in-vitro basophil histamine release and intracutaneous skin testing to protamine serially in an NPH-insulin dependent diabetic who had a severe, protracted anaphylactic reaction to protamine. At the time of his protamine reaction, his serum contained 8.5 ng/ml of anti-protamine IgE and 1.3 micrograms/ml of anti-protamine IgG antibody. One month following the reaction both anti-protamine IgE and IgG increased to 16 ng/ml (twofold rise) and 90.5 micrograms/ml (70-fold rise), respectively. With time, both anti-protamine IgE and IgG antibody declined. Serial intradermal skin tests using protamine sulphate did not discriminate between the protamine reactor and nine normal control subjects who had no prior exposure nor any demonstrable serum IgE antibody to protamine. In-vitro basophil histamine release to protamine sulphate was inconclusive in discriminating between the protamine reactor and normal control subjects. We postulate that protamine may be an incomplete or univalent antigen that must first combine with a tissue macromolecule or possibly heparin to become a complete multivalent antigen capable of eliciting IgE antibody-dependent mediator release.

Interactions between histamine and prostanoids in IgE-dependent, late cutaneous reactions in man

The contribution of histamine and cyclooxygenase metabolites of arachidonic acid to the wheal-and-flare reaction (WFR) (0 to 30 minutes) and the late cutaneous reaction (LCR) (1 to 24 hours) evoked by intradermal injection of antihuman IgE was appreciated in a comprehensive study of human volunteers treated with H1 and H2 antihistamines, cyclooxygenase inhibitors, as well as the combination of both types of drugs. The findings reinforce the concept that histamine is the major, but not exclusive, mediator of the WFR. In contrast, histamine accounted for but a limited portion of the LCR, but 48 hours of pretreatment with three different cyclooxygenase inhibitors, acetylsalicylic acid, indomethacin, or diclofenac sodium, had but a minor influence on the WFR, whereas all drugs produced a distinct overall inhibition of the LCR. However, for indomethacin, the inhibition was preceded by a potentiation (at 1 to 2 hours), which was abolished by antihistamines, suggesting increased histamine release from skin mast cells after cyclooxygenase inhibition. Furthermore, there was synergism between indomethacin and antihistamines during the LCR, and the combination of diclofenac sodium with antihistamines produced additive inhibition. It is proposed that cyclooxygenase products, such as prostaglandins and thromboxanes, contribute to IgE-dependent skin reactions, both as modulators of mediator release and as vasoactive mediators.