The autoimmune-prone MRL/Mp-lpr/lpr (MRL/lpr) mouse is characterized by the lpr mutation, which is a defect in the Fas antigen. Since Fas mediates apoptosis, this defect results in CD4-CD8- double negative T-cell proliferation, lupus nephritis, and macroscopic lupus erythematosus-like skin lesions. The control counterpart of MRL/lpr mouse is the MRL/Mp-+/+ (MRL/n) mouse, which lacks the lpr mutation and is almost normal during the first 6 mo of life. The lpr mutation, however, accelerates autoimmune phenomena in MRL/lpr mice. Thus, it is important to investigate autoimmune diseases like systemic lupus erythematosis in relation to the autoimmune disease-prone genetic background of MRL/n mice. We found that skin lesions in aged MRL/n mice had unique characteristics. The first characteristic is spontaneous occurrence, and the second is epidermal cell nuclear immunostaining with IgGs by direct immunofluorescence. The skin lesions in aged MRL/n mice showed milder inflammation than in MRL/lpr mice. A homogeneous pattern of epidermal cell nuclear staining was always associated with nuclear staining in kidney cells and also correlated with the in vitro binding of sera to keratinocytes cultured from newborn MRL/n mice. These results suggest that the skin lesions of aged MRL/n mice are a good model for certain types of cutaneous lupus erythematosus and also can provide new insights into the long-standing controversy whether epidermal cell nuclear staining occurs in vivo.
Widespread tense blisters developed on a 60-year-old Japanese man who had been diagnosed with pemphigus 11 years earlier, because of a history of pruritic erythema and erosions on his face, chest, and back, mild supra-basal layer blister formation found in a biopsy specimen, and a positive direct immunofluorescence test showing IgG deposition in the intercellular space. The histological findings showed subepidermal blister, and the immunoblot study detected 180kD bullous pemphigoid antigen. Direct immunofluorescence test revealed intercellular staining for IgG, and indirect immunofluorescence tests repeatedly demonstrated the presence of circulating antibodies to the intercellular space. From these observations, this case suggests the coexistence of pemphigus and bullous pemphigoid.
In this study, we investigated UVB-light-induced cytotoxicity and the binding of antibodies to extractable nuclear antigens on cultured keratinocytes from patients with cutaneous lupus erythematosus (LE). Keratinocytes from cutaneous LE patients showed a higher susceptibility to single-dose UVB light irradiation compared to keratinocytes from normal controls. The binding of antibodies to U1RNP and Ro/SS-A antigens on cultured keratinocytes was induced by UVB light and more up-regulated when cultured keratinocytes were reacted with autologous sera. Antibody-dependent cellular cytotoxicity (ADCC) was induced when cultured keratinocytes irradiated with UVB light were combined with autologous sera, using peripheral mononuclear cells of normal controls. Immunohistochemical studies of skin biopsy specimens from patients with systemic LE revealed an increased number of epidermal Langerhans cells at the peripheral sites of skin lesions and a relative dominance of infiltrative CD8-positive lymphocytes in the central area of skin lesions. Based on these findings we suggested that ADCC mechanisms were involved in the development of skin lesions, and the distribution of Langerhans cells and infiltrated CD8 cells were responsible for the expansion and persistence of lesions.
We examined the time-dependent dynamics of epidermal Langerhans' cells (LC) in human systemic lupus erythematosus (SLE), in MRL/Mp-lpr/lpr(MRL/lpr) mice, and in various experimental cutaneous inflammations, such as the Arthus reaction, dinitrochlorobenzene allergic dermatitis, and croton oil primary irritant dermatitis, in order to clarify the pathomechanisms of lupus skin lesions. The numbers of LC in untreated SLE patients with newly developed skin lesions decreased in the central lesional sites and increased significantly in the peripheral lesional sites. In MRL/lpr mice, the number of LC increased significantly in the central lesional sites during the initial stage and increased in the peripheral lesional sites and decreased in the central lesional sites 2-4 weeks after the onset of skin lesions. In contrast, with experimental cutaneous inflammations of guinea pigs, the increase in numbers of LC in the peripheral lesional sites was not significant during the time course of the reaction. These results suggest that the increased numbers of LC during the active and early stages of skin lesions in human SLE and MRL/lpr mice are closely related to the specific spontaneous development of skin lesions, unlike the dynamics of LC in experimental cutaneous inflammations.
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