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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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IgG4 autoantibodies show a lower pathogenic capacity compared with IgG1. In the upper panel, cryosections of human skin were incubated with IgG1 or IgG4 autoantibodies purified from patient 2, both adjusted at an end-point titer of 1:80 by IF microscopy. Subsequent addition of leucocytes leads to blister formation in cryosections treated with IgG1 autoantibodies (A). In contrast, IgG4 autoantibodies (B) fail to recruit leucocytes to the dermal–epidermal junction and to induce dermal–epidermal separation (magnification, ×400). The lower panel (C) shows the extent of dermal–epidermal separation after incubating the cryosections with IgG1 and IgG4 preparations from two BP patients (n = 4 sections/antibody preparation). Dermal–epidermal separation is represented as means ± SEM of the percent of the total length of the dermal–epidermal junction (DEJ) for each section. The reactivity of the antibody preparations as determined by their end-point titres by immunofluorescence microscopy is represented on the X-axis.
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fig06: IgG4 autoantibodies show a lower pathogenic capacity compared with IgG1. In the upper panel, cryosections of human skin were incubated with IgG1 or IgG4 autoantibodies purified from patient 2, both adjusted at an end-point titer of 1:80 by IF microscopy. Subsequent addition of leucocytes leads to blister formation in cryosections treated with IgG1 autoantibodies (A). In contrast, IgG4 autoantibodies (B) fail to recruit leucocytes to the dermal–epidermal junction and to induce dermal–epidermal separation (magnification, ×400). The lower panel (C) shows the extent of dermal–epidermal separation after incubating the cryosections with IgG1 and IgG4 preparations from two BP patients (n = 4 sections/antibody preparation). Dermal–epidermal separation is represented as means ± SEM of the percent of the total length of the dermal–epidermal junction (DEJ) for each section. The reactivity of the antibody preparations as determined by their end-point titres by immunofluorescence microscopy is represented on the X-axis.

Mentions: In our patients’ sera, we found lower titres of IgG1 when compared to titres of IgG4 autoantibodies (Table 2). To directly compare the pathogenic potential of autoantibodies of IgG1 and IgG4 subclass, IgG1 and IgG4 antibody preparations from two BP patients were used at similar titres. When incubated with the cryosections, IgG4 autoantibodies induced dermal–epidermal separation to a significantly lower extent when compared with IgG1 autoantibodies as assessed using the Fisher's exact test (P= 0.017) (Fig. 6).


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)

IgG4 autoantibodies show a lower pathogenic capacity compared with IgG1. In the upper panel, cryosections of human skin were incubated with IgG1 or IgG4 autoantibodies purified from patient 2, both adjusted at an end-point titer of 1:80 by IF microscopy. Subsequent addition of leucocytes leads to blister formation in cryosections treated with IgG1 autoantibodies (A). In contrast, IgG4 autoantibodies (B) fail to recruit leucocytes to the dermal–epidermal junction and to induce dermal–epidermal separation (magnification, ×400). The lower panel (C) shows the extent of dermal–epidermal separation after incubating the cryosections with IgG1 and IgG4 preparations from two BP patients (n = 4 sections/antibody preparation). Dermal–epidermal separation is represented as means ± SEM of the percent of the total length of the dermal–epidermal junction (DEJ) for each section. The reactivity of the antibody preparations as determined by their end-point titres by immunofluorescence microscopy is represented on the X-axis.
© Copyright Policy
Related In: Results  -  Collection

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fig06: IgG4 autoantibodies show a lower pathogenic capacity compared with IgG1. In the upper panel, cryosections of human skin were incubated with IgG1 or IgG4 autoantibodies purified from patient 2, both adjusted at an end-point titer of 1:80 by IF microscopy. Subsequent addition of leucocytes leads to blister formation in cryosections treated with IgG1 autoantibodies (A). In contrast, IgG4 autoantibodies (B) fail to recruit leucocytes to the dermal–epidermal junction and to induce dermal–epidermal separation (magnification, ×400). The lower panel (C) shows the extent of dermal–epidermal separation after incubating the cryosections with IgG1 and IgG4 preparations from two BP patients (n = 4 sections/antibody preparation). Dermal–epidermal separation is represented as means ± SEM of the percent of the total length of the dermal–epidermal junction (DEJ) for each section. The reactivity of the antibody preparations as determined by their end-point titres by immunofluorescence microscopy is represented on the X-axis.
Mentions: In our patients’ sera, we found lower titres of IgG1 when compared to titres of IgG4 autoantibodies (Table 2). To directly compare the pathogenic potential of autoantibodies of IgG1 and IgG4 subclass, IgG1 and IgG4 antibody preparations from two BP patients were used at similar titres. When incubated with the cryosections, IgG4 autoantibodies induced dermal–epidermal separation to a significantly lower extent when compared with IgG1 autoantibodies as assessed using the Fisher's exact test (P= 0.017) (Fig. 6).

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