Subacute cutaneous lupus erythematosus--the annular variant. A histological and ultrastructural study of five cases

Expression pattern of tissue-resident memory T cells in cutaneous lupus erythematosus

BACKGROUND

Tissue resident memory T cells (TRMs) persist long-term in peripheral tissues without recirculation, triggering an immediate protective inflammatory state upon the re-recognition of the antigen. Despite evidence incriminating the dysregulation of TRMs in autoimmune diseases, few studies have examined their expression in cutaneous lupus erythematosus (CLE).

OBJECTIVES

We aimed to examine whether there are differences among TRM populations in CLE depending on different clinical conditions, such as the CLE subtype or association with systemic lupus erythematosus, and to determine the effect of type I interferon (IFN) on the development of TRMs in CLE.

METHODS

CLE disease activity was evaluated using the Cutaneous Lupus Erythematosus Disease Area and Severity Index. The expression of the TRM markers CD69 and CD103 in CLE lesions was evaluated by immunofluorescence. Flow cytometry was performed on peripheral blood mononuclear cells after IFNα treatment.

RESULTS

The number of TRMs expressing either CD69 or CD103 was significantly higher in CLE lesions than in control skin; however, it was not significantly different between discoid lupus erythematosus and subacute CLE, or dependent on the presence of concomitant systemic lupus. Lesional severity was not correlated with an increase in TRMs in CLE. IFNα treatment induced a conspicuous increase in CD69 expression in skin-homing T cells, more profoundly in CD4+ T cells than in CD8+ T cells.

CONCLUSIONS

Skin TRMs, either CD69 or CD103-positive cells, showed increased levels in the lesional skin of CLE, and IFNα increased the expression of CD69 in T cells.

Cytomegalovirus infection induces expression of 60 KD/Ro antigen on human keratinocytes

To investigate the effect of human cytomegalovirus (CMV) infection on the expression of Ro autoantigen in human keratinocytes, the binding of anti-Ro peptide antibodies (anti-60 KD/Ro, anti-52 KD/Ro and anti-calreticulin) to cultured human keratinocytes was detected by fixed cell enzyme-linked immunoassay (ELISA), immunofluorescence, flow cytometry (FACS) analysis and immunoblotting. There was a significant increase in the binding of anti-60 KD/Ro antibody but not anti-52 KD/Ro or anti-calreticulin antibody to the surface of cultured keratinocytes at 24 h after CMV infection compared with uninfected cells, by ELISA and immunofluorescence. Surface binding of anti-60 KD/Ro was found in 71.2% (+/- 5.5%) of CMV-infected cells compared with 26.2% (+/- 4.1%) of untreated cells (P < 0.05) by FACS analysis. Similar observations were made with a human serum which contained anti-60 KD/Ro antibodies. Immunoblotting was used to analyse total cellular 60 KD/Ro antigen expression in keratinocytes infected with CMV or without infection. No increase in the intensity of the 60 KD band was found in extracts of the CMV-infected cells, suggesting that the 60 KD/Ro antigen is redistributed from the cytoplasm to the cell surface after viral infection. The effects of CMV infection on cell cultures were compared with those of ultraviolet B (UVB) irradiation. The 60 KD/Ro, 52 KD/Ro and calreticulin were all induced on the UVB-irradiated cell surface but not significant synergistic effect of UVB and CMV was found. This study provides evidence that CMV infection induced 60 KD/Ro antigen expression on the surface of human keratinocytes, suggesting that CMV may play a role in development of skin lesions in systemic lupus erythematosus (SLE).

Subacute cutaneous lupus erythematosus

Gilliam recognized subacute cutaneous lupus erythematosus (SCLE) as a lupus-specific eruption that identifies a unique subset of lupus erythematosus. These patients were noted to have prominent photoaggravated skin disease and often had musculoskeletal complaints, but generally did not develop significant systemic disease. SCLE patients were later found to have other distinctive features, including the frequent presence of anti-Ro antibodies, and enrichment for the human histocompatibility antigens (HLA) B8 and DR3. In the 13 years of published reports of SCLE patients following the initial study by Sontheimer et al (Subacute cutaneous lupus erythematosus: a cutaneous marker for a distinct lupus erythematosus subset. Arch Dermatol 115:1409-1415, 1979) a number of additional observations regarding SCLE patients have been made. These have included the recognition that SCLE may be associated with other rheumatic diseases, and that photoactive medications may induce lesions of SCLE. Areas of controversy concerning SCLE include conflicting studies regarding the histopathology of SCLE as compared to discoid lupus erythematosus (DLE), as well as the frequency of detection of anti-Ro antibodies in SCLE patients. Recent interesting studies of SCLE include a description of a unique pattern of immunoglobulin G (IgG) deposition on direct immunofluorescence, which may indicate the binding of anti-Ro antibodies to keratinocytes in vivo.