Ro/SSA antigen in human epidermis

[Neonatal lupus erythematosus and neurologic involvement: an incidental association?]

Neonatal lupus erythematosus is a rare disorder characterized by cutaneous lesions of the face and/or congenital heart block. The transplacental transfer of maternal anti-Ro/SSA, anti-La/SSB, or anti-U1RNP antibodies is responsible for the development of the disease. Few cases of neonatal lupus erythematosus with neurological involvement were reported in the medical literature.

CASE REPORT

A 36-week GA female infant presented with neonatal lupus erythematosus comprising cutaneous, hematologic and hepatic disorders with a favorable outcome. However, cutaneous atrophy and hyperpigmentation persisted. Spastic paraparesis was diagnosed at the age of six months.

CONCLUSION

The neurological lesions in neonatal lupus erythematosus could either be related to the presence of anti-Ro/SSA antibodies of maternal origin, or of anticardiolipin antibodies.

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).

Neonatal lupus erythematosus

Neonatal lupus erythematosus (NLE) is an autoimmune disease whose major findings are subacute cutaneous lupus erythematosus (SCLE) skin lesions and congenital heart block. Babies have maternal anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies. Anti-Ro/SSA are the predominant autoantibodies, having been found in about 95% of cases. The autoantibodies pass through the placenta from mother to child. Skin disease resolves at about the time that maternal autoantibodies can no longer be detected in the baby. NLE therefore provides the strongest clinical evidence that autoantibodies are involved in at least some manifestations of lupus erythematosus, but there is as yet no definitive evidence implicating autoantibodies in the disease process. Skin disease usually begins after birth, is transient, and does not result in scarring. Cardiac disease begins in utero, and the heart block is almost always permanent. Many babies require pacemakers, and about 10% die from complications related to cardiac disease. In some cases, transient liver disease or thrombocytopenia have been observed. Individuals who had NLE usually have healthy childhoods but may develop autoimmune disease in adulthood. Whether the later development of autoimmune disease is a common or an unusual event is not yet known. Mothers of babies with NLE may be asymptomatic initially, but with time usually develop symptoms of autoimmune disease. The most typical constellation of symptoms in our group of approximately 30 mothers of babies with NLE is that of Sjögren's syndrome. Most babies exposed to anti-Ro/SSA autoantibodies during gestation will not develop NLE. There is no test to determine prospectively which babies will be affected. Treatment during gestation is still controversial and, if attempted, should be reserved for fetuses with potentially life-threatening disease. Treatment after birth consists of topical management for skin disease and pacemaker implantation, if necessary, for heart block. Systemic steroids may be given for serious internal disease.

Pathomechanisms of photosensitive lupus erythematosus

This review discusses the mechanisms involved in different photosensitive lupus syndromes: acute cutaneous lupus erythematosus, chronic cutaneous (discoid) lupus erythematosus, subacute cutaneous lupus erythematosus, and neonatal lupus erythematosus. It is proposed that there are three principal determinants of photosensitivity in lupus: 1) susceptibility to UVR-induced release of epidermal and dermal cytokines; 2) susceptibility to UVR-induced release or translocation of sequestered antigens in the epidermis or dermis; and 3) different specific immunologic effector mechanisms, activated by cytokines and directed against discrete epidermal targets. Several characteristics of photosensitive lupus are discussed in detail: autoantibody specificities, autoantigen translocation, induction of epidermal intercellular adhesion molecule-a (ICAM-1), vascular activation, cytokine release and T-cell activation, and clinical phototesting. The role of antibodies to the extractable nuclear antigens Ro and La and the relationship to subacute cutaneous lupus erythematosus (SCLE) and neonatal lupus erythematosus is discussed in detail, and a model of SCLE is proposed.

Anti-Ro/SS-A antibodies in the pathophysiology of congenital heart block in neonatal lupus syndrome, an experimental model. In vitro electrophysiologic and immunocytochemical studies

OBJECTIVE

To determine whether anti-Ro/SS-A antibodies selectively bind to neonatal cardiac cells and alter membrane repolarization.

METHODS

An in vitro electrophysiologic and immunocytochemical experimental model contrasting neonatal and rabbit cardiac tissue was employed.

RESULTS

Sera and IgG-enriched fractions from anti-Ro/SS-A antibody-positive mothers of infants with neonatal lupus erythematosus and congenital heart block bind to neonatal, rather than adult, rabbit cardiac tissue and alter the transmembrane action potential (i.e., inhibit repolarization). The additional presence of anti-La/SS-B antibodies was not additive or synergistic for these immunocytochemical and electrophysiologic features. Sera containing other antibody specificities (i.e., anti-native DNA, cardiolipin, Sm, and nuclear RNP) failed to stain the neonatal cardiac tissue or produced alterations in membrane repolarization.

CONCLUSION

Anti-Ro/SS-A antibodies may play a pathophysiologic role in the development of congenital heart block in neonatal lupus.

IgG subclasses in the serum and skin in subacute cutaneous lupus erythematosus and neonatal lupus erythematosus

IgG subclasses differ in their biologic and chemical properties, such as complement fixation, protein and cellular binding, and placental transfer. In this study, IgG subclasses of anti-Ro/SSA antibodies in subacute cutaneous lupus (SCLE) and neonatal lupus (NLE) are examined in the serum and in the skin. IgG subclasses in NLE beginning in utero (NLE-heart disease) are compared to subclasses in NLE beginning after birth (NLE-skin disease). Human skin was grafted onto athymic mice, mice were injected with one of eight anti-Ro/SSA maternal NLE sera (four heart block, four skin disease) or seven anti-Ro/SSA SCLE sera, and grafts were examined for IgG subclasses using monoclonal anti-human IgG subclass reagents in an immunofluorescent technique. Lesional skin was examined from four SCLE patients. IgG1 was the only IgG subclass detected in the grafts and skin lesions. IgG1 was the predominant anti-Ro/SSA IgG subclass detected in SCLE and NLE sera in an ELISA using a synthetic Ro/SSA polypeptide. These studies show that the maternal anti-Ro/SSA autoantibodies in NLE-heart disease sera are predominantly IgG1 and are therefore likely to be present in the fetus at the time of gestation, when heart block usually develops. Second, differences in the clinical presentations of NLE (in utero vs. postnatal disease) cannot be attributed to differences in anti-Ro/SSA IgG subclasses. Finally, the subclass bound in the skin in SCLE is IgG1, a subclass capable of mediating tissue injury via complement or cellular effectors.

Maternal autoantibodies and pregnancy--II: The neonatal lupus syndrome

NLE is manifested most typically as transient subacute cutaneous lupus lesions or isolated complete congenital heart block. Babies with NLE have maternal anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies. It is presumed, but not proven, that transmission of these autoantibodies through the placenta to the baby has resulted in disease. However, other factors such as inflammatory cells or complement activation may be necessary for disease to be expressed. About half of babies reported with NLE have had heart disease and about half have had skin disease. There have been a few reports of liver disease and a few of thrombocytopenia. Any combination of these findings is possible in a given infant. Possibly, other haematologic abnormalities, pneumonitis or neurological disease could occur, but the evidence that these other abnormalities are part of NLE is scant. Mortality in NLE has occurred in babies with severe cardiac disease. It is estimated that 10% or more of babies with cardiac NLE die in infancy. Of the remainder, perhaps half will require permanent pacemaker implantation. Thus, there is substantial morbidity and mortality with cardiac NLE. The skin disease, by contrast, is not serious and typically leaves little or no residua. Individuals who have had NLE may develop connective tissue disease in adulthood. Whether this is a common or an unusual occurrence is not yet known, since a large cohort of individuals with NLE has not yet been followed into adulthood. Mothers of babies with NLE are often initially asymptomatic. With time, they frequently develop connective tissue disease symptoms. In our experience, these have been largely symptoms of Sjögren's syndrome and have generally not been debilitating. Most babies of mothers with anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies do not develop NLE. There is no way to determine prospectively which fetus or infant will be affected and which of those affected will have life-threatening disease. Systemic therapies should be reserved for those infants who have life-threatening manifestations of NLE. It is not yet known whether treatment of the mother during gestation will be beneficial or harmful to fetuses with severe NLE cardiac disease.

Binding of antibodies to the extractable nuclear antigens SS-A/Ro and SS-B/La is induced on the surface of human keratinocytes by ultraviolet light (UVL): implications for the pathogenesis of photosensitive cutaneous lupus

Autoantibodies to the non-histone nucleoprotein antigens SS-A/Ro, SS-B/La, and RNP are highly associated with photosensitive cutaneous lupus erythematosus (LE). In order to better understand the potential mechanisms of ultraviolet (UV) light on photosensitivity in patients with cutaneous LE, we designed immunopathologic in vitro and in vivo experiments to evaluate the effects of UV on the binding of such autoantibodies to the surface of human keratinocytes, one major target of immunologic damage in photosensitive LE. Short-term 2% paraformaldehyde fixation of suspensions of cultured human keratinocytes previously incubated with monospecific antiserum probes enabled the detection of ENA expression on the cell surface by flow-cytometry analysis. UVB light (280-320 nm) induced the binding of monospecific antibody probes for SS-A/Ro and SS-B/La on keratinocytes in a dose-dependent pattern with maximal induction observed at the dose of 200 mJ/cm2 UVB. Binding of SS-A/Ro, SS-B/La, and RNP antibody was augmented strongly, but binding of anti-Sm was very weak. In contrast, UVA (320-400 nm) light had no effect on the induction of binding of these antibody probes. Identical results were seen by standard immunofluorescence techniques. Hydroxyurea-treated keratinocytes showed similar induction of those antigens by UVB irradiation, which suggested that ENA expression on cultured keratinocytes by UVB were cell-cycle independent. Tunicamycin, an inhibitor of glycosylation of proteins, reduced UVB light effect on the SS-A/Ro and SS-B/La antigen's expression. These in vitro FACS analyses revealed that ENA augmentation on the keratinocyte cell surface was dose dependent, UVB dependent, glycosylation dependent, and cell-cycle independent. In vivo ENA augmentation on the keratinocyte surface was examined in suction blister epidermal roofs. Specific antibody probes for SS-A/Ro, SS-B/La, RNP, and Sm bound to human keratinocytes in intact suction blister epidermis following UVL irradiation in vivo. Using three different protocols, we have demonstrated that antibodies to SS-A/Ro, SS-B/La, and U1RNP bind to UVL-irradiated human keratinocytes. We speculate that this antibody binding is an important inducer of antibody dependent keratinocyte damage in photosensitive cutaneous lupus.

Anti-SS-A/Ro SS-B/La antibodies bind to neonatal rabbit cardiac cells and preferentially inhibit in vitro cardiac repolarization

The neonatal lupus syndrome is the most common cause of isolated congenital heart block. There is, at present, little information about the putative role of anti-SS-A/Ro SS-B/La antibodies in the pathogenesis of congenital heart block in the neonatal lupus syndrome. Using an in vitro experimental model, the present study was designed to test the hypothesis that IgG antibodies in the sera of anti-SS-A/Ro SS-B/La-positive mothers of infants with isolated congenital heart block bind to and affect the transmembrane action potential of rabbit cardiac tissue. The results demonstrate a preferential inhibition of membrane repolarization (ADP-50 and ADP-90) and staining of cardiac cells within the neonatal, in contrast to the adult, rabbit heart by sera and IgG-enriched fractions from anti-SS-A/Ro SS-B/La-positive individuals. The results of the electrophysiologic studies demonstrate a pathophysiologic role for the IgG fraction of anti-SS-A/Ro SS-B/La-positive maternal sera in inhibiting neonatal rabbit cardiac repolarization. It is possible that antibodies to similar determinants expressed on the cell membrane of cardiac-conducting cells also may play a pathophysiologic role in the development of idiopathic congenital heart block in humans.

Pattern of cutaneous immunoglobulin G deposition in subacute cutaneous lupus erythematosus is reproduced by infusing purified anti-Ro (SSA) autoantibodies into human skin-grafted mice

Subacute cutaneous lupus and neonatal lupus are closely associated with the presence of anti-Ro (SSA) autoantibodies, but there is no direct evidence establishing a role for anti-Ro (SSA) in these diseases. After parental injection into mice, IgG from sera containing anti-Ro (SSA) will bind human skin grafted onto the mice. To determine whether the antibody binding is due to anti-Ro (SSA), affinity-purified anti-Ro (SSA) and serum depleted of anti-Ro (SSA) were prepared. After injection into human skin-grafted mice, purified anti-Ro (SSA) antibodies bound an antigen in the human skin graft, while preabsorbing anti-Ro (SSA) serum with Ro (SSA) virtually abolished binding to the human skin graft. Moreover, the pattern of IgG deposition was primarily epidermal and was identical in the human skin-grafted mice injected with purified anti-Ro (SSA) when compared with that found in five patients with subacute lupus (four adults, one neonate). These data directly show that anti-Ro (SSA) antibodies bind to the skin, and support the hypothesis that anti-Ro (SSA) autoantibodies are involved in the disease process that produces subacute cutaneous lupus and neonatal lupus.