Effects of complement inactivation and IgG depletion on skin reactivity to autologous serum in chronic idiopathic urticaria.

Abstract

BACKGROUND:

Intradermal injection of autologous serum elicits a wheal-and-flare response in about 60% of patients with chronic idiopathic urticaria (CIU). This reactivity has been attributed to the presence of IgG autoantibodies directed against IgE or the alpha-chain of the high-affinity IgE receptor (FcepsilonRIalpha) expressed on basophils and mast cells, leading to the hypothesis that at least some forms of CIU could be sustained by an autoimmune process.

OBJECTIVES:

The aim of this study was to investigate the relationship between the presence of anti-IgE or anti-FcepsilonRI antibodies and the ability to induce wheal-and-flare responses in CIU sera selected for the capacity to give a positive skin test response.

METHODS:

Fifteen patients with CIU and a positive skin test response to autologous serum were injected intradermally with native serum and with serum heated at 56 degrees C for 30 minutes and then adsorbed on Sepharose-protein G to obtain IgG depletion. Serum levels of anti-IgE and anti-FcepsilonRIalpha antibodies were measured by ELISA by using purified IgE and recombinant RIalpha-soluble double-fusion protein RIalpha-human serum albumin-RIalpha, respectively. The histamine-releasing activity of sera was tested by using ELISA with whole human blood from a healthy donor.

RESULTS:

All patients had positive cutaneous responses to native serum injection. Anti-FcepsilonRIalpha antibodies were present in 14 of 15 native sera, only two of which were able to induce in vitro basophil degranulation. On the contrary, detectable amounts of anti-IgE antibodies were not found in any serum. IgG depletion by protein G resulted in complete (10/14 samples) or considerable (4/14 samples) removal of anti-FcepsilonRIalpha antibodies. The two sera endowed with functional activity lost their capacity to trigger histamine release from basophils after heating and protein G adsorption. Nonetheless, heat-decomplemented/IgG-depleted sera elicited wheal-and-flare reactions comparable with those observed with untreated sera.

CONCLUSIONS:

These results strongly suggest that skin reactivity to autologous serum could be due to as yet unidentified non-Ig reactants present in the sera of patients with CIU.

• Authors: U Fagiolo, F Kricek, C Ruf, A Peserico, A Amadori, M Cancian
• Journal: The Journal of allergy and clinical immunology (J Allergy Clin Immunol) Vol. 106 Issue 3 Pg. 567-72 (Sep 2000) ISSN: 0091-6749 [Print] United States
• PMID: 10984379 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies
• Antibodies, Anti-Idiotypic
• Autoantibodies
• Complement Inactivator Proteins
• Immunoglobulin G
• Receptors, IgE
• anti-IgE antibodies
• Histamine

Topics

• Adult
• Antibodies (blood)
• Antibodies, Anti-Idiotypic (blood, immunology)
• Autoantibodies (blood)
• Chronic Disease
• Complement Inactivator Proteins (pharmacology)
• Female
• Histamine (blood)
• Humans
• Immunoglobulin G (physiology)
• Male
• Middle Aged
• Receptors, IgE (immunology)
• Skin (immunology)
• Skin Tests
• Urticaria (blood, etiology)