Auteur : Pr. Amos GILHAR (Skin Research Laboratory Technion Faculty of Medicine P.O.B. 9649 HAIFA 31096 ISRAEL).
Travail subventionné par l’AAA (subvention 2004) à hauteur de 3 800 €.
Subvention débloquée le 08 janvier 2005.
Compte rendu fourni le 26 février 2006.
COMPTE RENDU DETAILLE (texte intégral)
The Role of Superantigen in the Induction of Alopacia Areata.
There is an increasing evidence regarding the role of infection in the pathogenesis of clinical relapses that occur in most auotimmune diseases, including psoriasis, multiple sclerosis, juvenile rheumatoid arthritis, type 1 diabetes and autoimmune thyroiditis. It has been proposed that superantigens might contribute to the pathogenesis of autoimmune disease by activating T cells that are specific for self antigens. Although there is no direct evidence of superantigens involvement, it has been suggested that superantigens could, under the right conditions, break the tolerance or suppression of auto-reactive T cell clones and induce a state of autoimmunity. Evidence for this hypothesis came from an animal model of multiple sclerosis: experimental autoimmune encephalomyelitis (EAE), where it was shown that administration of SEB to mice recovering from EAE triggered direct stimulation of the Vβ3 positive auto-reactive MBP peptide specific T cells resulting in a rapid relapse of the disease [73,74].
Alopecia areata is associated with loss of immune privilege in hair follicles. We previously demonstrated that interferon-gamma (INF-gamma) induces expression of MHC class I and II, resulting in loss of immune privilege and induction of AA in genetically susceptible female C3H/HeJ mice. It was proposed that treatment with Staphylococcal Enterotoxin B (SEB) superantigen would expand autoreactive T-cells and synergize with INF-gamma to induce AA. In order to address this issue, the C3H/HeJ mouse model has been utilized.
137 mice were included in this study which included two sets of experiments.
Seven week old mice were injected intravenously with either murine IFN-gamma 2 x 104 U (0.1 ml) or PBS (0.1 ml) for three consecutive days, followed by injections every 7 days for the full 14 weeks of the experiment.
30 days after the first injection the mice were subdivided into 3 groups for additional treatments as below:
Group 1: Injected intravenously with PBS during the first 30 days as above followed by PBS (0.1 ml) for 2 consecutive days and then injections with PBS every 7 days.
Group 2: Injected intravenously with murine IFN-gamma as above during the first 30 days followed by two days of INF-gamma (2 X 104 U/0.1 ml) then injections with IFN-gamma every 7 days.
Group 3: Injected intravenously with INF-gamma as above during the first 30 days followed by intraperitoneal injection with SEB (50 µg) for 2 days and then injections with INF-gamma every 7 days.
C) Fourteen weeks after starting the first injection, the skin was harvested. Grafts were analyzed by histology and immunohistochemical. The immunostaining endpoints were ICAM-1, MHC class I and class II (DR).
Two sets of experiments were performed. The first one included 91 C3H/HeJ (7wk of age) mice most of them were female. This experiment demonstrated development of hair loss exclusively in the male group. Therefore, we conducted a second study composed of only male C3H/HeJ mice. Hair loss was noted in 4/17 (23.5 %) mice in the INF-gamma injected mice versus 1/14 in the phosphate-buffered saline (PBS)-treated mice.The third group treated with IFN-gamma and SEB developed hair loss in 9/15 mice (60%).Various pattern of hair loss was observed in all groups including patchy hair loss around the head or diffuse pattern along the ventral or abdominal areas.
The immunohistochemical staining revealed dystrophic hair in anagen, associated with intra- and peri-follicular mononuclear cell infiltrates combined with many tellogen hair follicles in mice treated with SEB+INF-gamma Intra-follicular infiltrates were composed of CD8+ cells, and the peri-follicular infiltrates were predominantly CD4+ cells some of them were observed in close apposition with the outer root sheath Elevated expression of MHC class I and MHC class II were noted along the follicular epithelium especially on the outer root sheath, but also on the inner root sheath, and MHC class I was also expressed on the hair bulb. These findings are consistent with those previously reported for alopecia areata in C3H/HeJ mice and are similar to those reported for humans. In contrast, PBS-treated control mice exhibited minimal to no infiltrate, and no dystrophic anagen follicles. There was no expression of MHC class I and II on proximal follicular epithelium.
|GROUP||FIRST 30 DAYS
DAY 2 THEN EVERY 7 DAYS
|2 DAYS||10 WKS
EVERY 7 DAYS
|MICE WITH ALOPECIA|
|3||INF- gamma||SEB||INF- gamma||9/15|
Our previous study showed that injection of INF-gamma accelerated the development of alopecia areata in a genetically susceptible mouse strain. This was associated with expression of MHC class I and II in an immune privileged site (proximal hair follicle epithelium), and provides support for the hypothesis that loss of immune privilege can induce organ-specific autoimmune disease in a susceptible host. Previously it has been shown that superantigens play a role in the induction of autoimmunity. Indeed, the ability of superantigens to activate large numbers of T cells suggests that they may play a role in the course of autoimmune disorders. Data from several animal models of autoimmune disorders including experimental allergic encephalomyelitis and collagen induced arthritis supports this hypothesis. Administration of bacterial superantigens can induce an exacerbation of the autoimmune process in these models. Studies of several human disorders including rheumatoid arthritis, Kawasaki disease, insulin-dependent diabetes, and psoriasis lend support to the concept that bacterial superantigens may play a role in the pathogenesis of these diseases. Nevertheless, in some cases, depending on the timing of administration and the model, superantigens may lead to an amelioration of the autoimmune process. The presented data showed that treatment with INF-gamma plus SEB was superior to INF-gamma alone in inducing Alopecia Areata in a susceptible mouse strain. Based on these result it seems logical to conclude that superantigens can have a significant impact on the course of Alopecia Areata as an autoimmune mediated disorder. Furthermore, the results support the hypothesis of a two stage model for autoimmune disease.
ABSTRACT ACCEPTED FOR PRESENTATION AT THE SOCIETY FOR INVESTIGATIVE DERMATOLOGY MAY 2006, PHILADELPHIA, USA
Two stage model for induction of autoimmunity: SEB synergizes with interferon-gamma to induce alopecia areata
It was hypothesized that autoimmune T-cell diseases require two conditions, loss of tolerance to induce autoreactive T-cells, and a stimulus, such as superantigen, to expand the autoreactive T-cells. Alopecia areata (AA) is associated with loss of immune privilege in hair follicles. We previously demonstrated that interferon-gamma (INF-g) induces expression of MHC class I and II, resulting in loss of immune privilege and induction of AA in genetically susceptible female C3H/HeJ mice. It was proposed that treatment with Staphylococcal Enterotoxin B (SEB) superantigen would expand autoreactive T-cells and synergize with INF-g to induce AA. C3H/He mice 7 wk old were injected IV with murine IFN-g 2 x 104 U or PBS for three consecutive days, followed by injections every 7 days. 30 days following the first injection, the female and male mice were divided into three groups: Group 1: (PBS alone)Mice injected with PBS for 30 days received additional PBS injections IV for 2 consecutive days followed by injections with PBS every 7 days. Group 2: (INF-g alone) Mice treated 30 days with INF-g were injected IV with IFN-g for two days and followed by every 7 days. Group 3: (INF-g & SEB) Treated 30 days with INF-g, injected intraperitoneal with SEB (50 µg) for 2 days followed by injections with INF-g every 7 days. Mice were examined for hair loss. Skin was harvested 14 wks after the first injection skin and analyzed by histology as well as immunohistochemistry for ICAM-1, and MHC class I & II. Clinical rates of AA development on back and abdomen of C3H/He male mice; Group 1: PBS alone 7% (1/14), Group 2: INF-g alone 17% (3/17), Group 3: ING-g + SEB 46% (7/15), (p<0.05 for Group 3 vs. Group 1). Female mice did not demonstrate a difference between INF-G and (INF-g + SEB). INF-g plus SEB was superior to INF-g alone in inducing AA in a susceptible mouse strain. This supports the hypothesis of a two stage model for development of autoimmune disease.