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IgG4 autoantibodies induce dermal-epidermal separation.

Mihai S, Chiriac MT, Herrero-González JE, Goodall M, Jefferis R, Savage CO, Zillikens D, Sitaru C - J. Cell. Mol. Med. (2007 Sep-Oct)

Bottom Line: In these diseases, IgG1 and IgG3 isotypes, but not the IgG4 subclass, are thought to trigger inflammatory pathways resulting in tissue damage.Purified IgG4 did not fix complement, but, interestingly, like IgG1, activated leucocytes and induced dermal-epidermal separation.The potential of IgG4 autoantibodies to induce Fc-dependent dermal-epidermal separation was significantly lower compared to IgG1.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Lübeck, Lübeck, Germany.

ABSTRACT
Bullous pemphigoid (BP) is a sub-epidermal autoimmune blistering disease associated with autoantibodies to the dermal-epidermal junction (DEJ). Patients' autoantibodies induce dermal-epidermal separation when co-incubated with cryosections of human skin and leucocytes from healthy volunteers. IgG autoantibodies trigger complement and/or leucocyte activation resulting in specific pathology in several autoimmune conditions. In these diseases, IgG1 and IgG3 isotypes, but not the IgG4 subclass, are thought to trigger inflammatory pathways resulting in tissue damage. The capacity of IgG4 autoantibodies to mediate tissue damage has not yet been demonstrated. In this study, we isolated IgG1 and IgG4 autoantibodies from bullous pemhigoid patients'serum and analysed their blister-inducing potential in our cryosection assay. As expected, complement-fixing IgG1 autoantibodies induced sub-epidermal splits in this experimental model. Purified IgG4 did not fix complement, but, interestingly, like IgG1, activated leucocytes and induced dermal-epidermal separation. The potential of IgG4 autoantibodies to induce Fc-dependent dermal-epidermal separation was significantly lower compared to IgG1. Our results demonstrate that IgG4 autoantibodies are able to activate leucocytes and point to a hitherto less recognized function of IgG4. Moreover, for the first time, we clearly demonstrate that BP IgG4 autoantibodies have the capacity to induce leucocyte-dependent tissue damage.

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Purification of IgG1 and IgG4 autoantibodies specific to the epidermal basement membrane. IF microscopy study of serum from patient 1 on normal human skin demonstrates deposition of mainly IgG1 (A) and IgG4 (D) and traces of IgG2 (B) and IgG3 (C) at the dermal–epidermal junction. After purification against an affinity matrix containing mon-oclonal antibodies specific for IgG1, IgG1 autoantibodies to the skin basement membrane can be visualized in the purified fraction (E), while IgG2 (F), IgG3 (G) and IgG4 (H) autoantibodies are not detectable. Conversely, the antibody fraction purified against an affinity matrix specific for IgG4 demonstrated binding of autoantibodies to the basement membrane of normal human skin exclusively belonging to the IgG4 subclass (L), whereas no deposits of IgG1 (I), IgG2 (J) or IgG3 (K) were observed (all magnifications, ×200).
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fig01: Purification of IgG1 and IgG4 autoantibodies specific to the epidermal basement membrane. IF microscopy study of serum from patient 1 on normal human skin demonstrates deposition of mainly IgG1 (A) and IgG4 (D) and traces of IgG2 (B) and IgG3 (C) at the dermal–epidermal junction. After purification against an affinity matrix containing mon-oclonal antibodies specific for IgG1, IgG1 autoantibodies to the skin basement membrane can be visualized in the purified fraction (E), while IgG2 (F), IgG3 (G) and IgG4 (H) autoantibodies are not detectable. Conversely, the antibody fraction purified against an affinity matrix specific for IgG4 demonstrated binding of autoantibodies to the basement membrane of normal human skin exclusively belonging to the IgG4 subclass (L), whereas no deposits of IgG1 (I), IgG2 (J) or IgG3 (K) were observed (all magnifications, ×200).

Mentions: BP autoantibodies predominantly belong to the IgG1 and IgG4 subclasses, while IgG2 and IgG3 autoantibodies are only occasionally found [27]. Therefore, in the present study, IgG1 and IgG4 antibodies were purified by immunoaffinity chromatography from serum of 3 and 5 BP patients, respectively. IgG subclass preparations were shown to contain IgG autoantibodies of a single subclass, as determined by haemagglutination assay and/or IF microscopy, respectively (Table 1 and 2). A representative example is depicted in Figure 1. Unless otherwise stated, reactivities of IgG1 and IgG4 autoantibodies used for cryosection experiments were similar in antibody preparations and original BP serum (Table 2).


IgG4 autoantibodies induce dermal-epidermal separation.

Mihai S, Chiriac MT, Herrero-González JE, Goodall M, Jefferis R, Savage CO, Zillikens D, Sitaru C - J. Cell. Mol. Med. (2007 Sep-Oct)

Purification of IgG1 and IgG4 autoantibodies specific to the epidermal basement membrane. IF microscopy study of serum from patient 1 on normal human skin demonstrates deposition of mainly IgG1 (A) and IgG4 (D) and traces of IgG2 (B) and IgG3 (C) at the dermal–epidermal junction. After purification against an affinity matrix containing mon-oclonal antibodies specific for IgG1, IgG1 autoantibodies to the skin basement membrane can be visualized in the purified fraction (E), while IgG2 (F), IgG3 (G) and IgG4 (H) autoantibodies are not detectable. Conversely, the antibody fraction purified against an affinity matrix specific for IgG4 demonstrated binding of autoantibodies to the basement membrane of normal human skin exclusively belonging to the IgG4 subclass (L), whereas no deposits of IgG1 (I), IgG2 (J) or IgG3 (K) were observed (all magnifications, ×200).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401274&req=5

fig01: Purification of IgG1 and IgG4 autoantibodies specific to the epidermal basement membrane. IF microscopy study of serum from patient 1 on normal human skin demonstrates deposition of mainly IgG1 (A) and IgG4 (D) and traces of IgG2 (B) and IgG3 (C) at the dermal–epidermal junction. After purification against an affinity matrix containing mon-oclonal antibodies specific for IgG1, IgG1 autoantibodies to the skin basement membrane can be visualized in the purified fraction (E), while IgG2 (F), IgG3 (G) and IgG4 (H) autoantibodies are not detectable. Conversely, the antibody fraction purified against an affinity matrix specific for IgG4 demonstrated binding of autoantibodies to the basement membrane of normal human skin exclusively belonging to the IgG4 subclass (L), whereas no deposits of IgG1 (I), IgG2 (J) or IgG3 (K) were observed (all magnifications, ×200).
Mentions: BP autoantibodies predominantly belong to the IgG1 and IgG4 subclasses, while IgG2 and IgG3 autoantibodies are only occasionally found [27]. Therefore, in the present study, IgG1 and IgG4 antibodies were purified by immunoaffinity chromatography from serum of 3 and 5 BP patients, respectively. IgG subclass preparations were shown to contain IgG autoantibodies of a single subclass, as determined by haemagglutination assay and/or IF microscopy, respectively (Table 1 and 2). A representative example is depicted in Figure 1. Unless otherwise stated, reactivities of IgG1 and IgG4 autoantibodies used for cryosection experiments were similar in antibody preparations and original BP serum (Table 2).

Bottom Line: In these diseases, IgG1 and IgG3 isotypes, but not the IgG4 subclass, are thought to trigger inflammatory pathways resulting in tissue damage.Purified IgG4 did not fix complement, but, interestingly, like IgG1, activated leucocytes and induced dermal-epidermal separation.The potential of IgG4 autoantibodies to induce Fc-dependent dermal-epidermal separation was significantly lower compared to IgG1.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University of Lübeck, Lübeck, Germany.

ABSTRACT
Bullous pemphigoid (BP) is a sub-epidermal autoimmune blistering disease associated with autoantibodies to the dermal-epidermal junction (DEJ). Patients' autoantibodies induce dermal-epidermal separation when co-incubated with cryosections of human skin and leucocytes from healthy volunteers. IgG autoantibodies trigger complement and/or leucocyte activation resulting in specific pathology in several autoimmune conditions. In these diseases, IgG1 and IgG3 isotypes, but not the IgG4 subclass, are thought to trigger inflammatory pathways resulting in tissue damage. The capacity of IgG4 autoantibodies to mediate tissue damage has not yet been demonstrated. In this study, we isolated IgG1 and IgG4 autoantibodies from bullous pemhigoid patients'serum and analysed their blister-inducing potential in our cryosection assay. As expected, complement-fixing IgG1 autoantibodies induced sub-epidermal splits in this experimental model. Purified IgG4 did not fix complement, but, interestingly, like IgG1, activated leucocytes and induced dermal-epidermal separation. The potential of IgG4 autoantibodies to induce Fc-dependent dermal-epidermal separation was significantly lower compared to IgG1. Our results demonstrate that IgG4 autoantibodies are able to activate leucocytes and point to a hitherto less recognized function of IgG4. Moreover, for the first time, we clearly demonstrate that BP IgG4 autoantibodies have the capacity to induce leucocyte-dependent tissue damage.

Show MeSH
Related in: MedlinePlus