The cytotoxic effect of neonatal lupus erythematosus and maternal sera on keratinocyte cultures is complement-dependent and can be augmented by ultraviolet irradiation

Clinical perspectives and murine models of lichenoid tissue reaction/interface dermatitis

A set of histopathological elements, that is death of epidermal basal cell layer keratinocytes and inflammatory cell infiltration, distinguishes lichenoid tissue reaction (LTR)/interface dermatitis (IFD) from other inflammatory mucocutaneous diseases with histological findings of superficial perivascular dermatitis. The LTR/IFD is observed in inflammatory mucocutaneous diseases such as lichen planus, Stevens-Johnson syndrome/toxic epidermal necrolysis, acute graft-versus-host disease, lupus erythematosus and dermatomyositis. Clinical and basic researches have suggested that keratinocytes are antigen-presenting cells and mediate LTR/IFD reaction via production of cytokines/chemokines and inhibitory molecules such as programmed cell death (PD)-L1, and that cytotoxic CD8(+) T cells producing cytotoxic granules, perforin, granzyme B and granulysin are final effector cells to cause keratinocyte death. Because interferon-γ and FasL, which are produced by not only CD8(+) but also CD4(+) T cells, are candidates of the pathogenic molecules in LTR/IFD, CD4(+) T cells may also play a role to develop LTR/IFD. On the other hand, CD4(+) Treg cells accelerate the remission of LTR/IFD. Some murine models of LTR/IFD have been established. For example, LTR/IFD reactions were induced in keratinocyte-specific membrane-binding ovalbumin-transgenic (mOVA Tg) mice by adoptive transfer of CD8(+) T cells with OVA-specific T-cell-receptor. It has also been shown that human CD8(+) T cells are pathogenic immune cells in human skin-xenografted mice. Various immunosuppressants are used to treat patients with mucocutaneous diseases with LTR/IFD. By analysis of the mOVA Tg mice, a JAK inhibitor was suggested to be a new candidate drug to inhibit not only pathogenic T cells but also keratinocyte death in LTR/IFD. More specific treatments for patients with LTR/IFD will be developed in future.

The intracellular 52-kd Ro/SSA autoantigen in keratinocytes is up-regulated by tumor necrosis factor ? via tumor necrosis factor receptor I

OBJECTIVE

Previous studies have shown that the nuclear Ro/SSA autoantigens involved in photosensitive cutaneous lupus manifestations are regulated by ultraviolet B (UVB) irradiation. UVB exposure triggers the release of tumor necrosis factor alpha (TNFalpha) from keratinocytes in the epidermis and from mast cells in the dermis. The present study aimed to characterize the effect of TNFalpha on messenger RNA (mRNA) and protein expression of the intracellular 52-kd Ro/SSA autoantigen in primary human keratinocytes and to elucidate the TNFalpha receptor (TNFR) signaling pathways mediating this effect.

METHODS

Expression of 52-kd Ro/SSA mRNA in primary human keratinocytes was investigated by quantitative real-time polymerase chain reaction (LightCycler system) using GAPDH as the housekeeping gene. Expression of 52-kd Ro/SSA protein was studied by flow cytometry after staining intracellular protein with IgG purified from an anti-52-kd Ro/SSA-positive serum. TNFR function was assessed by culturing cells in the presence and absence of neutralizing antibodies directed against the TNFR subunits TNFRI and TNFRII.

RESULTS

TNFalpha-induced up-regulation of 52-kd Ro/SSA mRNA expression peaked at 4 hours, followed by up-regulation of intracellular 52-kd Ro/SSA protein expression at 24 hours, independently of apoptosis. Between different donors, a high variability of both constitutive expression levels and TNFalpha-induced changes in 52-kd Ro/SSA mRNA and protein expression was observed. The up-regulatory effect of TNFalpha on 52-kd Ro/SSA mRNA and protein expression was inhibited by anti-TNFRI antibodies but enhanced by anti-TNFRII antibodies.

CONCLUSION

The finding that TNFalpha up-regulates 52-kd Ro/SSA expression in keratinocytes via TNFRI suggests that it may play a role in the pathogenesis of anti-Ro/SSA-associated cutaneous lupus erythematosus.

Photosensitivity in cutaneous lupus erythematosus: lessons from mice and men

Mouse models are similar but not identical to human diseases. However, they are important for research into the pathogenesis underlying autoimmune diseases because they allow us to evaluate similarities and differences between human diseases and mouse models. In fact, experimental models and inbred lupus-prone mice are tools that enable a better understanding of the 'photosensitivity' or 'photocytotoxicity' phenomena in relation to autoimmunity. Genetic studies of MRL/lpr mice revealed that the appearance of macroscopic lupus erythematosus (LE)-like skin lesions needs the lpr mutation plus an additional factor in an autosomal dominant fashion. The candidate is ultraviolet (UV) B light, the susceptibility to which is regulated by the genetic background. Such a genetic background is also speculated to be important in human cutaneous LE patients. The translocation of anti-SS-A/Ro on cultured keratinocytes irradiated with UVB light is quantitatively different from photocytotoxicity, and the quantitative levels are significantly higher in systemic LE and subacute cutaneous LE than in discoid LE and normal controls. This review focuses on the lessons gleaned from mouse and human models, and discusses photosensitivity in human cutaneous LE.

Keratinocytes from patients with lupus erythematosus show enhanced cytotoxicity to ultraviolet radiation and to antibody-mediated cytotoxicity

Keratinocyte cytotoxicity is an important component of the immunopathology of photosensitive lupus erythematosus, and antibody-dependent cell-mediated cytotoxicity (ADCC) has been shown to be an important mechanism by which autoantibodies, especially those specific for SS-A/Ro, can induce keratinocyte damage in models of photosensitive lupus. We provide further evidence that keratinocytes from patients with photosensitive lupus show significantly greater ultraviolet radiation (UVR)-induced cytotoxicity, and that ADCC of these targets is especially enhanced by autologous patient's serum or by anti-SS-A/Ro+ sera. Keratinocytes from normal uninvolved skin of 29 patients with cutaneous lupus erythematosus (LE) were grown in cell culture and tested as targets in cytotoxicity experiments in vitro. Cultured keratinocytes from patients with systemic lupus erythematosus (SLE) and subacute cutaneous lupus erythematosus (SCLE) showed significantly greater cytotoxicity following UVR treatment than did keratinocytes from normal adult controls or from neonatal foreskins (P < 0.01). The same cultures also showed greater UVR-induced binding of IgG from fractionated anti-SS-A/Ro+ preparations. ADCC experiments were also performed using keratinocytes cultured from patients with SLE, SCLE, discoid lupus erythematosus (DLE), and normal controls. When keratinocytes were incubated in autologous serum plus a standard mononuclear cell effector population, the percentage of ADCC observed was significantly greater in cultures containing keratinocytes and sera from the SLE and SCLE patients (P < 0.001). When cultured keratinocytes were added to different IgG antibody probes, plus standard mononuclear effector populations, greater ADCC was seen using the anti-SS-A/Ro probe and keratinocytes from patients with SLE or SCLE. With normal human neonatal keratinocyte targets, the anti-SS-A/Ro probe induced greater ADCC than that seen with anti-ssDNA or normal human serum. We have shown that keratinocytes from patients with some forms of lupus erythematosus (SLE and SCLE) show greater cytotoxicity in vitro when irradiated with UVR, and greater susceptibility to ADCC whether the antibody source is their own serum or an anti-SS-A/Ro probe.