An unexpected twist in alopecia areata pathogenesis: are NK cells protective and CD49b+ T cells pathogenic?

Natural killer (NK) cells have become a recent focus of interest in alopecia areata (AA) research. To further investigate their role in an established mouse model of AA, lesional skin from older C3H/HeJ mice with AA was grafted to young C3H/HeJ female mice, and NK cells were depleted by continuous administration of rabbit anti-asialo GM1. As expected, this significantly reduced the number of pure NK cells in murine skin, as assessed by NKp46 quantitative immunohistochemistry. Quite unexpectedly, however, the onset of hair loss in C3H/HeJ mice was accelerated, rather than retarded. NK cell depletion was accompanied by a significant increase in the number of perifollicular CD49b+T cells in the alopecic skin of anti-asialo GM1-treated mice. These findings underscore the need to carefully distinguish in future AA research between pure NK cells and defined subsets of CD49b+ lymphocytes, as they may exert diametrically opposed functions in hair follicle immunology and immunopathology.

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.

Effect of non-steroidal anti-inflammatory drugs on natural killer cell activity in patients with dementia.

BACKGROUND: Alteration of innate and acquired immunity can play a role in the mechanism involved in the development of dementia. Epidemiologic studies indicate that the use of non-steroidal anti-inflammatory drugs can delay the onset or slow progression of Alzheimer disease. OBJECTIVES: To determine whether the use of NSAIDs is associated with natural killer activity alteration in AD and multi-infarct vascular dementia patients, as compared with non-demented elderly and healthy young people. METHODS: In this prospective open study four groups of subjects (AD, VD, non-demented elderly, and healthy young people) were treated with an NSAID drug (rofecoxib 12.5 mg/day or ibuprofen 400 mg twice daily) for 7 days. Natural killer cell cytotoxicity was measured after flow cytometry analysis before and after treatment. RESULTS: Of the 49 subjects studied, 15 had a diagnosis of AD (3 men, 12 women; mean age 83.5 +/- 8.1 years), 15 had a diagnosis of multi-infarct VD (7 men, 8 women; mean age 75.5 +/- 8.4), 13 were non-demented elderly (1 man, 12 women; mean age 80.2 +/- 7.2), and 6 were healthy young volunteers (3 men, 3 women; mean age 36.8 +/- 4.4). While all examined subjects showed decreased NK cell cytotoxicity after treatment, this decrease was most prominent and statistically significant in elderly patients suffering from vascular dementia--from an average of 30.5 +/- 11.8% before treatment to 22.5 +/- 16% after treatment (P = 0.04). The decrease in NK cell cytotoxicity was only moderate and not statistically significant in all other elderly and young subjects. Young healthy volunteers exhibited a significantly higher total NK cytotoxicity before and after treatment compared to all age groups (P < 0.001). CONCLUSION: These findings suggest that NSAIDs decrease NK activity in vascular dementia patients. Our findings also suggest that natural killer activity alteration cannot explain the ability of anti-inflammatory drugs to delay the onset or slow the progression of AD.

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.

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.

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.

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.