Systemic lupus erythematosus is a multisystem autoimmune disease in which the autoantibody response targets a variety of autoantigens of diverse subcellular location. We show here that these autoantigens are clustered in two distinct populations of blebs at the surface of apoptotic cells. The population of smaller blebs contains fragmented endoplasmic reticulum (ER) and ribosomes, as well as the ribonucleoprotein, Ro. The larger blebs (apoptotic bodies) contain nucleosomal DNA, Ro, La, and the small nuclear ribonucleoproteins. These autoantigen clusters have in common their proximity to the ER and nuclear membranes, sites of increased generation of reactive oxygen species in apoptotic cells. Oxidative modification at these sites may be a mechanism that unites this diverse group of molecules together as autoantigens.

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Autoantigens targeted in systemic lupus erythematosus are clustered in two populations of surface structures on apoptotic keratinocytes.

The complement system plays a paradoxical role in the development and expression of autoimmunity in humans. The activation of complement in systemic lupus erythematosus (SLE) contributes to tissue injury. In contrast, inherited deficiency of classical pathway components, particularly C1q (ref. 1), is powerfully associated with the development of SLE. This leads to the hypothesis that a physiological action of the early part of the classical pathway protects against the development of SLE (ref. 2) and implies that C1q may play a key role in this respect. C1q-deficient (C1qa-/-) mice were generated by gene targeting and monitored for eight months. C1qa-/- mice had increased mortality and higher titres of autoantibodies, compared with strain-matched controls. Of the C1qa-/- mice, 25% had glomerulonephritis with immune deposits and multiple apoptotic cell bodies. Among mice without glomerulonephritis, there were significantly greater numbers of glomerular apoptotic bodies in C1q-deficient mice compared with controls. The phenotype associated with C1q deficiency was modified by background genes. These findings are compatible with the hypothesis that C1q deficiency causes autoimmunity by impairment of the clearance of apoptotic cells.

Homozygous C1q deficiency causes glomerulonephritis associated with multiple apoptotic bodies

A guide to biological skin substitutes.

Systemic autoimmune diseases are a genetically complex, heterogeneous group of diseases in which the immune system targets a diverse, but highly specific group of intracellular autoantigens. The clustering and marked concentration of these molecules in the surface blebs of apoptotic cells, and their modification by apoptosis-specific proteolytic cleavage and/or phosphorylation at these sites, has focused attention on a unique apoptotic setting as the potential initiating stimulus for systemic autoimmunity. This apoptotic event is likely to (i) occur in a microenvironment containing high concentrations of the targeted antigens, (ii) be pro-immune in nature (e.g. viral infection), and (iii) allow suprathreshold concentrations of antigen with non-tolerized structure (either novel fragments, post-translational modifications, or complexes) to enter the class II processing pathway and initiate a primary immune response. Defective clearance or reduced anti-inflammatory consequences of apoptotic material may be important susceptibility factors in this group of diseases. Once the primary immune response to apoptotic antigens has been initiated, other apoptotic events (occurring in the course of homeostasis or damage) may stimulate the secondary immune response with less stringency, resulting in flares.

/pdf/autoantigens-as-substrates-for-apoptotic-proteases-2pk7nl6t50.pdf

Autoantigens as substrates for apoptotic proteases: implications for the pathogenesis of systemic autoimmune disease

Improved survival of patients with extensive burn injuries requires the development of better techniques for timely and permanent closure of the full-thickness wound. We developed procedures for establishing confluent, stratified layers of cultured, autologous keratinocytes on the surface of a modified collagen-glycosaminoglycan membrane that contains autologous fibroblasts. We transferred the composite grafts onto limited areas of excised full-thickness burn wounds of four patients with extensive burn injuries. Our results indicate that this composite graft material has acceptable "take," with formation of a basement membrane within 9 days of graft placement. Use of this technique for major wound coverage may offer a significant advance in the care of extensively burned patients and also may be useful for providing skin for reconstructive surgery. ( JAMA . 1989;262:2125-2130)

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=JAMA&articleId=379044&pdfFileName=jama_262_15_032.pdf

Burn Wound Closure With Cultured Autologous Keratinocytes and Fibroblasts Attached to a Collagen-Glycosaminoglycan Substrate

Antibodies which bind to different nuclear antigens in tissue sections or in permeabilized cell cultures are useful markers of subsets of connective tissue disease, especially of lupus erythematosus (LE), but whether these antibodies are able to react with these intracellular sequestered antigens in vivo and cause immunologic tissue damage has been a matter of much debate. We report experiments which show that ultraviolet light-irradiated, cultured human keratinocytes bind IgG antibodies from the sera of LE patients with either monospecific anti-SSA/Ro, anti-RNP, or anti-Sm activity, which implies that these antigens have been made accessible on the cell surface by ultraviolet irradiation. Normal human sera or LE patient's sera with anti-double-stranded DNA, anti-single-stranded DNA, or antihistone activity do not bind to the surface of irradiated human keratinocytes. In control experiments, all antisera produced the expected patterns of nuclear and cytoplasmic staining of fixed permeabilized, unirradiated keratinocytes. Careful study of the viability and permeability of irradiated keratinocytes by several techniques showed that this apparent cell membrane expression of extractable nuclear antigens (SSA/Ro, RNP, and Sm) following irradiation was seen on injured keratinocytes whose cell membranes were intact, but not on dead cells. It is particularly significant that all six monospecific anti-SSA/Ro sera bound to irradiated keratinocytes, since this antibody antigen system is highly associated with photosensitive cutaneous LE.

/pdf/ultraviolet-light-induces-binding-of-antibodies-to-selected-yv5awuhtq6.pdf

Ultraviolet light induces binding of antibodies to selected nuclear antigens on cultured human keratinocytes.

Infants with neonatal lupus erythematosus have congenital heart block, transient cutaneous lesions, or both Mothers of these infants have SSA/Ro autoantibodies that are passed across the 

Immunogenetics of the Neonatal Lupus Syndrome

Study of HLA-DR Synthesis in Cultured Human Keratinocytes

Neonatal lupus erythematosus is a disease of infants characterized by congenital heart block, transient cutaneous lesions, or both. The syndrome is related to the passage of maternal autoantibodies across the placenta to the fetus, and its resolution usually occurs within 6 months, when the infant becomes seronegative. The autoantibody associated with neonatal lupus is anti-SSA/Ro. Mothers of infants with the disease may have Sjogren's syndrome or systemic lupus erythematosus, but they are often asymptomatic. Fewer than 100 cases of neonatal lupus have been reported, which probably underestimates the prevalence of the disease. It is important to recognize the syndrome because newborns may develop complete heart block with congestive heart failure and residual scarring or pigment changes of the skin. They may also be at risk for developing systemic lupus erythematosus later in life. To define more clearly the pathogenesis and genetic influences in neonatal lupus, the present authors studied six families with the disease (almost 10 per cent of the reported cases). Seven children from the six families were examined clinically, serologically, and by HLA typing. The findings in these infants and their six mothers are given in Table 1.

William L. Weston

Papers

Ultraviolet light induces binding of antibodies to selected nuclear antigens on cultured human keratinocytes.

Immunogenetics of the Neonatal Lupus Syndrome

Study of HLA-DR Synthesis in Cultured Human Keratinocytes

Immunogenetics of the Neonatal Lupus Syndrome