Antihuman IgE is often used to study basophil- and mast cell-mediator release in vitro but is infrequently used in vivo. To evaluate in vivo skin reactivity to anti-IgE, an affinity purified rabbit F(ab′)2 fragment of antihuman IgE was injected intradermally in 22 nonallergic and 27 allergic,subjects. All 49 subjects (including a subject with <1 nglml of total serum IgE) had positive immediate cutaneous reactions to anti-IgE. Although total serum IgE level was weakly correlated (r = -0.51; p < 0.005) with in vivo skin reactivity to anti-IgE for the entire population, allergic subjects did not have significantly increased skin reactivity compared to nonallergic subjects (p = 0.18), despite having higher total serum IgE levels (p < 0.002). A late-phase cutaneous response (LPR) to anti-IgE occurred in 60% of the allergic and in 50% of the nonallergic subjects. Subjects with an LPR required approximately tenfold higher concentrations of anti-IgE to produce an immediate wheal of 10 mm compared to subjects who did not develop an LPR (p = 0.02), suggesting that the concentration of the stimulus injected is more important for the development of a LPR than the size of the immediate cutaneous response. Skin reactivity to codeine phosphate (a non-IgE-dependent secretogogue) was correlated with skin reactivity to anti-IgE (r = 0.47; p < 0.05), suggesting that in vivo skin mast cell degranulation is partially a function of mast cell releasability. No adverse reactions to intradermal injection of rabbit F(ab′)2 antihuman IgE occurred, and no increase in serum IgG antibodies to rabbit gamma globulin could be detected 3 weeks after skin testing. Antihuman IgE is therefore a skin test reagent that can be safely used to evaluate skin mast cell degranulation and LPR in vivo in nonatopic individuals and in those subjects whose allergic sensitivities are unknown.
ASJC Scopus subject areas
- Immunology and Allergy