Lymphocytes, neuropeptides, and genes involved in alopecia areata.

Many lessons in autoimmunity - particularly relating to the role of immune privilege and the interplay between genetics and neuroimmunology - can be learned from the study of alopecia areata, the most common cause of inflammation-induced hair loss. Alopecia areata is now understood to represent an organ-restricted, T cell-mediated autoimmune disease of hair follicles. Disease induction is associated with collapse of hair follicle immune privilege in both humans and in animal models. Here, the role of HLA associations, other immunogenetic factors, and neuroendocrine parameters in alopecia areata pathogenesis are reviewed. This instructive and clinically significant model disease deserves more widespread interest in the immunology community.

Alopecia areata: a tissue specific autoimmune disease of the hair follicle.

The goal of this review is to introduce the immunologic community to alopecia areata as a model system for the study of tissue directed autoimmune disease. Alopecia areata is marked by autoimmune assault on the hair follicle resulting in hair loss. It is linked to HLA-DQ3 and evidence suggests it is mediated by T-lymphocytes with a TH1 cytokine profile. Hair follicles are an immune protected site with deficient MHC expression. Evidence is presented suggesting that alopecia areata results from loss of immune privilege with presentation of autoantigens. Alopecia areata is one of the most common human autoimmune conditions, with a lifetime risk of approximately 1.7%. Study of alopecia areata in humans is facilitated by the accessibility of scalp for biopsy. It is possible to transfer the condition with lesional human lymphocytes in a human scalp graft/SCID mouse model. There are also spontaneous animal models which share the features of the human condition. For these reasons, alopecia areata is a powerful model for study of the induction and pathogenesis of tissue directed autoimmune disease.

Psoriasis is mediated by a cutaneous defect triggered by activated immunocytes: induction of psoriasis by cells with natural killer receptors.

This study was performed to ask whether psoriasis is a unique pathologic response of epidermis of psoriatic patients, or cells with natural killer receptors can induce psoriatic changes in skin from nonpsoriatic donors. Human nonlesional skin from five psoriatics, as well as from seven nonpsoriatics was grafted on to beige-SCID mice. Lymphocyte lines with natural killer activity, and mixed natural killer, natural killer T cell phenotype, were generated by culture of peripheral blood mononuclear cells from both psoriatic, and normal donors, in 100 U interleukin-2 per ml for 14 d. Natural killer cells were injected into the human skin grafts, and the grafts were harvested after 4 wk. Injection of natural killer cells from psoriatic donors into autologous nonlesional psoriatic skin resulted in classic psoriasis histology with a significant increase in epidermal thickness, and proliferation, as well as expression of epidermal human leukocyte antigen DR, intercellular adhesion molecule-1, CD1d, and K-16. Superantigen stimulation was not necessary. In contrast, injection of natural killer cells from normal donors into autologous normal skin did not induce the histology of psoriasis, but that of psoriasiform dermatitis. This is a nonspecific reaction pattern. These grafts also exhibited a significant increase in epidermal thickness, and proliferation. Differences from psoriasis included mild epidermal edema (spongiosis), hypergranulosis, irregular elongation of rete ridges, and lack of thinning of the suprapapillary plate. Injection of allogeneic natural killer cells into grafts also resulted in psoriasiform dermatitis, regardless of the source of natural killer cells, or skin. Psoriasis induction by cells with natural killer receptors appears to be dependent upon the source of skin. This suggests that psoriasis results from a cutaneous defect that is triggered by an autoimmune activation.

Aging of human epidermis: reversal of aging changes correlates with reversal of keratinocyte fas expression and apoptosis.

The goal of this study was to determine the role of Fas-mediated apoptosis in human epidermal aging. Epidermal Fas expression and apoptosis are increased in aged human skin. Aging changes of human epidermis, including decreased epidermal thickness and proliferation, are reversed following grafting of human skin to SCID (severe combined immunodeficiency) mice. Skin from aged participants (n = 14; mean 70.7 years), and young participants (n = 14; mean 23.4 years) was grafted to beige SCID mice, and epidermal thickness, proliferation (Ki-67 expression), apoptosis (TUNEL [Tdt-mediated dUTP nick end labeling] reaction below granular layer), and expression of Fas and FasL were determined by histology and immunochemical staining. Aged skin was associated with thinning of the epidermis, decreased epidermal proliferation, a significant increase in apoptosis below the granular layer, and epidermal Fas expression. Engraftment significantly reversed these aging changes, including apoptosis, and Fas expression. Correlation of reversal of aging changes, with decreased epidermal Fas expression and apoptosis, supports a role for Fas-mediated apoptosis in aging of human epidermis.

Mediation of alopecia areata by cooperation between CD4+ and CD8+ T lymphocytes: transfer to human scalp explants on Prkdc(scid) mice.

OBJECTIVE: To determine the role of CD4+ and CD8+ T lymphocytes in the pathogenesis of alopecia areata. DESIGN: Relapse of alopecia areata was induced in autologous human scalp grafts on Prkdc(scid) mice by injection of activated T lymphocytes derived from lesional skin. CD4+ and CD8+ T cells were separated by magnetic beads before injection. SETTING: University-based dermatology practice. PARTICIPANTS: Eleven patients with either alopecia totalis or severe alopecia areata. MAIN OUTCOME MEASURES: Hair regrowth, hair loss, and immunohistochemical findings of scalp explants. INTERVENTION: Transfer of scalp T cells to autologous lesional scalp explants on Prkdc(scid) mice. RESULTS: Injection of unseparated T cells and mixed CD4+ plus CD8+ T cells resulted in significant hair loss (P<.01) in 5 of 5 experiments. However, injection of purified CD4+ or CD8+ T cells alone did not result in reproducible hair loss. CD4+ and CD8+ T cells induced follicular expression of intercellular adhesion molecule 1 (CD54), HLA-DR, and HLA-A, HLA-B, and HLA-C after injection into scalp grafts. CONCLUSIONS: CD4+ and CD8+ T cells have a role in the pathogenesis of alopecia areata. It is hypothesized that CD8+ T cells act as the effector cells, with CD4+ T cell help. It is now necessary to look for HLA-A, HLA-B, and HLA-C associations with alopecia areata. Therapeutic manipulations that interfere with CD8+ activity should be examined.

Clues from alopecia areata on the role of neuropeptides in the initiation of autoimmunity.

A fascinating question regarding the pathogenesis of alopecia areata is the potential linkage with the brain. Siebenharr et al. demonstrate that substance P fibers are increased in early lesions, and that substance P treatment induces catagen follicles along with activated CD8+ T cells. Potentially, neuropeptides serve as the initial insult resulting in loss of tolerance and autoimmune disease.

Fas pulls the trigger on psoriasis.

Fas/FasL signaling is best known for induction of apoptosis. However, there is an alternate pathway of Fas signaling that induces inflammatory cytokines, particularly tumor necrosis factor (TNF)-alpha and interleukin (IL)-8. This pathway is prominent in cells that express high levels of anti-apoptotic molecules such as Bcl-xL. Because TNF-alpha is central to the pathogenesis of psoriasis and psoriatic epidermis has a low apoptotic index with high expression of Bcl-xL, we hypothesized that inflammatory Fas signaling mediates induction of psoriasis by activated lymphocytes. Noninvolved skin from psoriasis patients was grafted to beige-severe combined immunodeficiency mice, and psoriasis was induced by injection of FasL-positive autologous natural killer cells that were activated by IL-2. Induction of psoriasis was inhibited by injection of a blocking anti-Fas (ZB4) or anti-FasL (4A5) antibody on days 3 and 10 after natural killer cell injection. Anti-Fas monoclonal antibody significantly reduced cell proliferation (Ki-67) and epidermal thickness, with inhibition of epidermal expression of TNF-alpha, IL-15, HLA-DR, and ICAM-1. Fas/FasL signaling is an essential early event in the induction of psoriasis by activated lymphocytes and is necessary for induction of key inflammatory cytokines including TNF-alpha and IL-15.

Alopecia areata: autoimmunity--the evidence is compelling.

There is strong evidence indicating that alopecia areata is a tissue-specific, autoimmune disease. Hair loss is associated with a perifollicular lymphocytic infiltrate made up primarily of CD4+ cells, along with a CD8+ intrafollicular infiltrate. Evidence of immune activation includes expression of HLA-DR; HLA-A,B,C; and ICAM-1 on the follicular epithelium. It is likely that the follicular expression of HLA-DR and ICAM-1 is induced by interferon-gamma produced by T cells. Antibodies to follicular epithelium are often present, but their significance is not known. Lesional scalp from alopecia areata patients grafted onto nude mice regrows hair coincident with a loss of infiltrating lymphocytes from the graft. Hair loss can be transferred to human scalp explants on SCID mice by injection of lesional T cells. It is necessary to activate the T cells by culture with follicular autoantigens. Melanocyte-associated antigens are also capable of activating T cells to induce hair loss, suggesting that they are capable of functioning as autoantigens for alopecia areata. Parallel evidence in rodent models of spontaneous alopecia areata also strongly supports a role for T cells in the pathogenesis of this condition.

Minocycline inhibits antigen processing for presentation to human T cells: additive inhibition with chloroquine at therapeutic concentrations.

The ability of minocycline to inhibit processing of tetanus toxoid (TT) for presentation to human T cells was tested. Peripheral blood antigen presenting cells (APC) were incubated with TT before or after addition of test compounds for 4 h. APC were then fixed with paraformaldehyde, and added to autologous TT-responsive T cell lines for a proliferation assay. Minocycline (0.1-0.4 mM) gave significant inhibition of T cell response to TT and was equivalent to chloroquine. Inhibition was not observed when TT was incubated with APC before minocycline, indicating that presentation of preprocessed antigen was not inhibited. Minocycline, doxycycline, and tetracycline all inhibited the proliferation of PBMC to TT. The combination of minocycline and chloroquine resulted in additive inhibition at clinically relevant levels of both drugs (3.7 microM). This study suggests a novel immunosuppressive mechanism for minocycline, as well as possible additive anti-inflammatory effect when combined with chloroquine or hydroxychloroquine.

Immune-mediated loss of transgene expression in skin: implications for cutaneous gene therapy.

A clearer understanding of the immune-mediated loss of transgene from cutaneous epithelium is necessary for development of effective clinical gene therapy protocols for patients who carry null mutations in the target gene. We have used retrovirus-mediated transfer of lacZ to mouse skin as a model to investigate the mechanism of immune-mediated transgene loss in skin. Transduction of C57Bl/6 mouse skin resulted in elicitation of both humoral and cellular immune responses. Antibody responses did not play a major role in the loss of transgene. Infiltration of the transduced skin with CD4(+) and CD8(+) cells and induction of transgene-specific cytotoxic T lymphocytes implied a role for T-cell-mediated responses. Transduction of mice deficient in either major histocompatibility complex (MHC) class I or class II molecules resulted in transient transgene expression. Only in MHC(-/-) mice lacking expression of both class I and class II MHC molecules was persistent transgene expression seen. These data indicate a primary role for T-cell-mediated responses in the immune-mediated loss of transgene expression. Furthermore, CD4 and CD8 T cells have overlapping roles and either population can effectively eliminate transduced cells. Therefore, long-term cutaneous gene therapy may require development of strategies to interfere with activation or function of both T cell populations.

Transfer of alopecia areata in the human scalp graft/Prkdc(scid) (SCID) mouse system is characterized by a TH1 response.

Alopecia areata is an autoimmune condition directed at hair follicles, which results in loss of hair. We have previously demonstrated that it is possible to transfer hair loss, along with the immunohistologic findings of alopecia areata, to human scalp grafts on Prkdc(scid) (SCID) mice by injection of autologous activated lesional T-cells. This study examines the cytokine profile of T-cells and follicular epithelium following transfer of hair loss. Two consistent findings significantly (P < 0.01) associated with hair loss were production of interferon-gamma-inducible protein-10 kDa (IP-10) by follicular epithelium (13/13), and production of INF-gamma by infiltrating T-cells (10/12). Noninjected control grafts regrew hair, and were generally negative for IP-10 (positive 2/9), and INF-gamma (positive 2/9), but expressed of IL-10 on the follicular epithelium (7/9). These data support an INF-gamma TH1 pathogenesis for hair loss in alopecia areata.

Human T lymphocyte response to Borrelia burgdorferi infection: no correlation between human leukocyte function antigen type 1 peptide response and clinical status.

We tested the hypothesis that cross-reactivity between the outer surface protein A (OspA) of Borellia burgdorferi and human leukocyte function antigen (LFA) type 1 mediates chronic autoimmune sequelae of Lyme disease. T cell response was studied in subjects with Lyme disease presenting with erythema migrans alone (n=36), erythema migrans with neurological disease (n=12), and chronic Lyme disease syndrome (n=20), as well as healthy control subjects from Lyme-endemic (n=50) and -nonendemic (n=18) regions. Antigens included recombinant OspA and OspC (all strain B31) and human LFA-1 peptide (IYVIEGTSKQDLTSF). Proliferation to OspA was detected in 11 (28%) of 39 of subjects presenting with erythema migrans, which increased to 50% at 4 weeks of follow-up. Reactivity to OspA and LFA-1 was significantly correlated (P<.001) and was observed in 18 (78%) of 23 of OspA-responsive subjects. However, there was no correlation between T cell response to human LFA-1 peptide and clinical status.