Autoimmunity to type VII collagen in SKH1 mice is independent of regulatory T cells

Abstract

SummaryEpidermolysis bullosa acquisita is an autoimmune blistering disease characterized by circulating and skin basement membrane-bound IgG autoantibodies to type VII collagen, a major structural protein of the dermal-epidermal junction. Regulatory T cells (T reg ) suppress self antigen-mediated autoimmune responses. To investigate the role of T reg in the the autoimmune response to type VII collagen in a mouse model, a monoclonal antibody against mouse CD25 was used to deplete T reg . A recombinant mouse type VII collagen NC1 domain protein and mouse albumin were used as antigens. SKH1 mice were used as a testing host. Group 1 mice received NC1 immunization and were functionally depleted of T reg ; group 2 mice received NC1 immunization and rat isotype control; and group 3 mice received albumin immunization and were functionally depleted of T reg . Results demonstrated that anti-NC1 IgG autoantibodies with high titres, as determined by enzymelinked immunosorbent assay and Western blotting, developed in all mice immunized with NC1 (groups 1 and 2), but were undetected in group 3 mice. The predominant subclasses of anti-NC1 autoantibodies were IgG1, IgG2a and IgG2b; furthermore, these antibodies carried only the kappa light chain. IgG autoantibodies in the sera of NC1-immunized mice reacted with mouse skin basement membrane in vitro and deposited in skin basement membrane in vivo as detected by indirect and direct immunofluorescence microscopy, respectively. Our data suggest that the development of autoimmunity against type VII collagen in mice is independent of T reg function and the autoimmune response is mediated by both Th1 and Th2 cells. We speculate that the basement membrane deposition of IgG may eventually lead to blister development.

Evidence for pathogenicity of autoreactive T cells in autoimmune bullous diseases shown by animal disease models

“…Meanwhile, Chen et al . have reported that the depletion of Tregs by anti‐mouse CD25 antibody did not affect the production of anti‐COL7 antibody in SKH1 mice immunized with mouse COL7, suggesting that the development of autoimmunity against COL7 in mice is independent of Treg function. Hence, the role of Tregs in the induction and/or the progression of AIBDs should be further investigated.…”

Experimental models of epidermolysis bullosa acquisita

“…The addition of other adjuvants like CpG, pertussis or cholera toxins increases the efficacy of the immunization and results in SJL‐1 mice in a stronger autoimmune response and a more extensive blistering skin disease (Sesarman A and Sitaru C, unpublished). Various inbred and outbred mouse strains, including BALB/c, C57BL/6, SJL‐1, AJ and SKH‐1, are prone to develop an autoimmune response upon immunization with murine type VII collagen (56,70). However, the genetic background appears to strongly influence the development of the blistering disease in these mice.…”

“…Thus, SJL‐1 mice qualify as high responders with an incidence of 80–100%, whereas only about 50% of the immunized BALB/c mice develop a significantly milder disease (56). In contrast, other strains, including C57BL/6 and the outbred SKH‐1 mice, are completely resistant to the induction of experimental EBA by immunization (56,70). All mice developed circulating IgG autoantibodies that recognized type VII collagen and bound to the lamina densa of the dermal–epidermal junction.…”

Epidermolysis Bullosa Acquisita Associated with Psoriasis

“…However, the role of Treg cells in EBM remains unclear. Depletion of the Treg cells with an antibody did not affect the autoimmune response type VII collagen in a mouse model (11). This mouse model reproduced auto-antibody production against type VII collagen, but not blistering ( 12).…”