Classical and alternate pathway activation of complement in pemphigus vulgaris lesions

Complement Activation in Autoimmune Bullous Dermatoses: A Comprehensive Review

Autoimmune bullous dermatoses (AIBD) are characterized by circulating autoantibodies that are either directed against epidermal antigens or deposited as immune complexes in the basement membrane zone (BMZ). The complement system (CS) can be activated by autoantibodies, thereby triggering activation of specific complement pathways. Local complement activation induces a pathogenic inflammatory response that eventually results in the formation of a sub- or intraepidermal blister. Deposition of complement components is routinely used as a diagnostic marker for AIBD. Knowledge from different animal models mimicking AIBD and deposition of complement components in human skin biopsies provides more insight into the role of complement in the pathogenesis of the different AIBD. This review outlines the role of the CS in several AIBD including bullous pemphigoid, epidermolysis bullosa acquisita, mucous membrane pemphigoid (MMP), pemphigus, linear IgA-disease, and dermatitis herpetiformis. We also discuss potential therapeutic approaches targeting key complement components, pathways and pathogenic complement-mediated events.

Critical Role of the Neonatal Fc Receptor (FcRn) in the Pathogenic Action of Antimitochondrial Autoantibodies Synergizing with Anti-desmoglein Autoantibodies in Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a life-long, potentially fatal IgG autoantibody-mediated blistering disease targeting mucocutaneous keratinocytes (KCs). PV patients develop pathogenic anti-desmoglein (Dsg) 3 ± 1 and antimitochondrial antibodies (AMA), but it remained unknown whether and how AMA enter KCs and why other cell types are not affected in PV. Therefore, we sought to elucidate mechanisms of cell entry, trafficking, and pathogenic action of AMA in PV. We found that PVIgGs associated with neonatal Fc receptor (FcRn) on the cell membrane, and the PVIgG-FcRn complexes entered KCs and reached mitochondria where they dissociated. The liberated AMA altered mitochondrial membrane potential, respiration, and ATP production and induced cytochrome c release, although the lack or inactivation of FcRn abolished the ability of PVIgG to reach and damage mitochondria and to cause detachment of KCs. The assays of mitochondrial functions and keratinocyte adhesion demonstrated that although the pathobiological effects of AMA on KCs are reversible, they become irreversible, leading to epidermal blistering (acantholysis), when AMA synergize with anti-Dsg antibodies. Thus, it appears that AMA enter a keratinocyte in a complex with FcRn, become liberated from the endosome in the cytosol, and are trafficked to the mitochondria, wherein they trigger pro-apoptotic events leading to shrinkage of basal KCs uniquely expressing FcRn in epidermis. During recovery, KCs extend their cytoplasmic aprons toward neighboring cells, but anti-Dsg antibodies prevent assembly of nascent desmosomes due to steric hindrance, thus rendering acantholysis irreversible. In conclusion, FcRn is a common acceptor protein for internalization of AMA and, perhaps, for PV autoantibodies to other intracellular antigens, and PV is a novel disease paradigm for investigating and elucidating the role of FcRn in this autoimmune disease and possibly other autoimmune diseases.

Role of direct immunofluorescence on Tzanck smears in pemphigus vulgaris

The Tzanck smear is a simple, sensitive, and rapid test to diagnose pemphigus vulgaris (PV), a life threatening autoimmune blistering disorder. The presence of acantholytic cells in cytology is indicative of but not specific for PV. Hence, a direct Immunofluorescence (DIF) test to demonstrate immunoglobulin deposits on the acantholytic cells would make the Tzanck test more specific, in addition to being a rapid test. Twenty untreated patients with PV confirmed histopathologically were enrolled to evaluate the efficacy of using DIF technique using IgG on Tzanck smear samples. The DIF smears were compared with DIF on skin biopsies in the same patient. This prospective pilot study approved by the institutional ethics committee was carried out in a tertiary health care hospital in a developing country. Of the 15 patients presenting within 3 mo of onset of the illness, 40% (n = 6) showed DIF positivity on Tzanck smear, when compared with 46.67% (n = 7) on skin biopsy. On the other hand, of the five patients presenting beyond 3 mo of their illness, only 20% (n = 2) showed positivity on Tzanck, when compared with all 100% (n = 5) on skin biopsy. The study, thus, suggests that DIF on skin biopsy is comparable to biopsy in diagnosing early PV. This preliminary study proposes that the use of DIF on Tzanck smear is a simple, rapid, painless, and user-friendly out-patient procedure for the diagnosis of early PV, even for relatively inaccessible lesions in the oral cavity and flexural regions. This methodology would be of great help in outlying and rural facilities lacking proper histological equipment, thus avoiding the need for a surgical or punch biopsy or heavy investment in laboratory equipment and expertise. Probable reasons for DIF negativity on Tzanck smears are also discussed.

A possible mechanism for phenol-induced pemphigus

A possible mechanism for phenol-induced pemphigus lesions in genetically predisposed individuals is proposed that accounts for in vitro observations and cases of biochemical acantholysis, as well as the in vivo acantholysis in pemphigus induced by phenols. The mechanism involves the induction of interleukin-1a and tumor necrosis factor-a release by keratinocytes. These cytokines in turn have been shown to be involved in the regulation and synthesis of complement and proteases like plasminogen activator, which have been implicated in the pathogenesis of acantholysis in pemphigus vulgaris.

Mechanisms of blister induction by autoantibodies

Autoimmune diseases are characterized by defined self-antigens, organ specificity, autoreactive T cells and/or autoantibodies that can transfer disease. Autoimmune blistering diseases are organ-specific autoimmune diseases associated with an immune response directed to structural proteins mediating cell-cell and cell-matrix adhesion in the skin. While both autoreactive T and B cells have been detected and characterized in patients with autoimmune blistering diseases, current evidence generally supports a pathogenic role of autoantibodies for blister formation. The immunopathology associated with blisters induced by autoantibodies relies on several mechanisms of action. Autoantibodies from patients with pemphigus diseases can exert a direct effect just by binding to their target mediated by steric hindrance and/or by triggering the transduction of a signal to the cell. In most subepidermal autoimmune blistering conditions, in addition to the binding to their target antigen, autoantibodies need to interact with factors of the innate immune system, including the complement system and inflammatory cells, in order to induce blisters. Generally, decisive progress has been made in the characterization of the mechanisms of blister formation in autoimmune skin diseases. However, various aspects, including the exact contribution of steric hindrance and signal transduction for pemphigus IgG-induced acantholysis or the fine tuning of the inflammatory cascade triggered by autoantibodies in some subepidermal blistering diseases, still need to be addressed. Understanding the mechanisms by which autoantibodies induce blisters should facilitate the development of more specific therapeutic strategies of autoimmune blistering diseases.

Pemphigus can be induced by topical phenol as well as by foods and drugs that contain phenols or thiols

Pemphigus is an autoimmune disease that results from the interaction between predisposing genetic factors and exogenous factors, the most common environmental factors being drugs and food. Topical phenol has induced pemphigus in one patient. Drugs and foods that induce pemphigus are divided into three main groups according to their chemical structure: thiols (containing a sulfhydryl group), phenol, nonthiol nonphenol. Thiol and phenol compounds can induce acantholysis in tissue cultures in vitro. The suggested mechanisms for thiol acantholysis include direct biochemical impairment of cell adhesion, protease activation and immunological reaction with the formation of a neoantigen. Possible mechanisms of phenol-induced pemphigus include the induction of IL-1alpha and TNF-alpha release by keratinocytes. These cytokines have been shown to be relevant in the regulation and synthesis of complement and proteases, like plasminogen activator, which has been implicated in the pathogenesis of acantholysis in pemphigus vulgaris. Avoiding exposure of genetically predisposed individuals to these factors is important in treating and preventing this disease.

Immunofluorescence in dermatology

The accurate diagnosis of bullous and other immune diseases of the skin requires evaluation of clinical, histologic, and immunofluorescence findings. Immunofluorescence testing is invaluable in confirming a diagnosis that is suspected by clinical or histologic examination. This is especially true in subepidermal bullous diseases that often have overlap in the clinical and histologic findings. Direct immunofluorescence is performed on perilesional skin for patients with bullous diseases and lesional skin for patients with connective tissue diseases and vasculitis.

In vitro and in vivo expression of interleukin-1alpha and tumor necrosis factor-alpha mRNA in pemphigus vulgaris: interleukin-1alpha and tumor necrosis factor-alpha are involved in acantholysis

Keratinocyte-derived cytokines have been implicated in the pathogenesis of a number of skin diseases. In this study we examined the possible role of keratinocyte-derived cytokines in the development of acantholysis in pemphigus vulgaris. Nineteen patients with pemphigus vulgaris, demonstrating the characteristic clinical, pathologic, and immunopathologic findings were studied. In situ immunolabeling demonstrated the presence of two cytokines interleukin-1alpha and tumor necrosis factor-alpha, in lesional and perilesional areas. Results were confirmed by reverse transcriptase-polymerase chain reaction, demonstrating overexpression of both cytokines in vivo. To study the role of these cytokines in the pathogenesis of pemphigus vulgaris both in vitro and in vivo studies were performed. The results of the in vitro study demonstrated that pemphigus vulgaris IgG induced interleukin-1alpha and tumor necrosis factor-alpha mRNA in the skin. The potential pathogenic role of these mediators was demonstrated by a blocking study using antibodies against human interleukin-1alpha and tumor necrosis factor-alpha in keratinocytes cultures. A combination of anti-interleukin-1alpha and anti-tumor necrosis factor-alpha antibodies inhibited in vitro pemphigus vulgaris IgG induced acantholysis. To confirm the role of interleukin-1 and tumor necrosis factor-alpha in pemphigus, we utilized passive transfer studies using interleukin-1 deficient mice (ICE-/-, interleukin-1beta-/-) and tumor necrosis factor-alpha receptor deficient mice (TNFR1R2-/-). Both groups demonstrated a decreased susceptibility to the passive transfer of pemphigus. Our data support the role of cytokines interleukin-1 and tumor necrosis factor-alpha in the pathogenesis of pemphigus vulgaris.

Non-infectious diseases of the oral soft tissue: a new approach

A significant proportion of the non-infectious diseases of oral mucosa are either auto-immune in nature or have lesions which are the result of immunologically-mediated events. These include pemphigus, benign mucous membrane pemphigoid, linear IgA bullous dermatosis, dermatitis herpetiformis, epidermolysis bullosa acquisita, erythema multiforme, and lichen planus. Although each of these has certain specific characteristics, all may produce bullae, erosions, and ulcers on the oral mucosa, resulting in confusingly similar clinical presentations. With careful clinical, histological, and immunofluorescence examination, it is possible to establish a definitive diagnosis in a high proportion of cases. However, one of the most exciting developments which has emerged from recent research into these diseases is their precise molecular characterization. This raises the prospect of accurate, highly specific diagnostic tests which would provide the basis for sound clinical management, with original approaches replacing the somewhat unsatisfactory symptomatic treatment which is often all that is available.

Granulocyte activation in bullous diseases: release of granular proteins in bullous pemphigoid and pemphigus vulgaris

BACKGROUND

Eosinophil and polymorphonuclear granulocytes may be involved in the formation of blisters in bullous dermatoses, particularly bullous pemphigoid.

OBJECTIVE

Our purpose was to evaluate the role of granulocyte activation in the pathogenesis of pemphigus vulgaris and bullous pemphigoid.

METHODS

Levels of eosinophil cationic protein (ECP) and neutrophil-derived myeloperoxidase (MPO) in blister fluid and serum and levels of serum IgE were determined in patients with bullous pemphigoid (n = 12), those with pemphigus vulgaris (n = 9) and healthy volunteers (n = 12).

RESULTS

In blister fluid and serum of patients with bullous pemphigoid, significantly elevated concentrations of ECP, MPO and IgE were detected as compared with controls. In contrast, ECP, MPO, and IgE levels in blister fluid and serum of patients with pemphigus vulgaris did not significantly differ from controls. Moreover, the MPO/ECP ratio in serum of patients with bullous pemphigoid was significantly decreased as compared with controls, whereas the MPO/ECP ratio in pemphigus vulgaris did not differ from controls, indicating a preferential activation of eosinophils in bullous pemphigoid only. In patients with bullous pemphigoid, serum levels of ECP and MPO significantly decreased during immunosuppressive therapy to levels similar to those of controls.

CONCLUSION

Activated granulocytes, releasing their granular contents such as ECP and MPO, may be of importance for blister formation in bullous pemphigoid and may be useful for monitoring disease activity.

Immunohistologic and ultrastructural comparison of the dermal papilla and hair follicle bulb from "active" and "normal" areas of alopecia areata

The "active" edges of patches of alopecia areata and normal areas from the same scalp (i.e., bearing normal terminal hair) from seven patients with alopecia areata were investigated immunohistologically. Similar areas from a further eight patients were examined using light and electronmicroscopy. "Active" and "normal" areas of alopecia areata scalps were immunohistologically similar and varied from normal controls in the number, distribution, and ratio for T4 and T8-positive cells. Similarly the ultrastructural changes seen in the "active" areas when compared to normal controls were also present in the "normal" areas of alopecia areata scalps. The most significant differences found between normal "control" follicles and both "active" and "normal" areas of alopecia areata scalps were the polymorphic nature of the dermal papilla cells and the loss of cellular organization within the dermal papillae taken from alopecia areata scalps. In addition, the junction between the dermal papilla and the bulb of the hair follicle, the dermo-epithelial junction of the hair follicle bulb, demonstrated critical changes in follicles taken from both "active" and "normal" areas of alopecia areata scalps. These results support the suggestion of a subclinical state of alopecia areata and indicate that further work on the etiology of alopecia areata should be directed towards the "normal" areas of alopecia areata scalps, in particular the cells of the dermal papilla and the dermo-epithelial junction of the hair follicle bulb.

Vesiculobullous mucocutaneous disease: pemphigus vulgaris

Pemphigus vulgaris is a potentially fatal autoimmune mucocutaneous disease in which oral lesions may be the initial and predominant manifestation. The disease is characterized by acantholysis in the immediately suprabasal layers of the stratified squamous epithelium, giving rise to blisters which readily rupture leaving erosions which show little tendency to heal. Immunogenetic studies indicate a marked genetic susceptibility to the disease, with the immune response-associated HLA-DR4 and DRw6 alleles being especially important. The trigger for autoantibody formation is unknown. The antigen in pemphigus vulgaris is probably a 130-140 kD cell adhesion molecule located in the cell membrane of basal and immediately suprabasal keratinocytes. Antibody binding to this antigen is likely to interfere with normal intercellular adhesion, leading to desmosomal detachment. Propagation of acantholysis and cell damage are attributable to complement activation, with deposition of the membrane attack complex on the keratinocyte cell membrane, and proteolysis due to increased plasminogen activator production. Steroid therapy is the treatment of choice, but significant mortality is still associated with the disease.

Deposition of the membrane attack complex of complement in pemphigus vulgaris and pemphigus foliaceus skin

The present study was performed to determine whether complement activation in pemphigus vulgaris (PV) and pemphigus foliaceus (PF) results in the assembly of the terminal complement sequence or membrane attack complex (MAC) in skin lesions. Biopsy specimens of skin lesions from five patients with PV and three patients with PF contained C5, C7, C9, and the MAC related neoantigen (C5b-9 neoantigen) in intercellular substance areas (ICS), as well as IgG and the early complement components Clq, C4, and C3. The presence of these late complement components and the C5b-9 neoantigens in ICS sites of the skin lesions is indicative of complement activation by the pemphigus antibody, with subsequent assembly of the MAC. The binding of IgG and early complement components to ICS was observed in both non-lesional (normal appearing) skin and in skin lesions. However, no MAC could be detected in the normal appearing skin of our pemphigus patients. It was also noted that the MAC could be generated in vitro on cryostat sectioned normal human skin by pemphigus antibody in the presence of complement. Results of these studies suggest that complement activation may be related to membrane damage of epidermal cells in both PV and PF.

Comparison of IgG subclasses and complement binding activity of autoantibodies from patients with bullous pemphigoid and pemphigus

Bullous pemphigoid and pemphigus are autoimmune disorders of skin of unknown etiology and are characterized by the presence of immunoreactants in the skin and circulating autoantibodies to skin components. The distribution of IgG subclass antibodies to intercellular substance (ICS) of pemphigus and basement membrane zone substance (BMZ) of bullous pemphigoid was analyzed by using monoclonal antibodies to human IgG subclasses. IgG4 type anti-BMZ antibody was found in the majority of patients with bullous pemphigoid (88% in skin and 96% in serum). One third to one half of bullous pemphigoid patients had IgG1 and IgG2 anti-BMZ antibodies. The majority of bullous pemphigoid skin (92%) had complement in skin, however only one third of their sera had complement binding activity in vitro. IgG1 anti-ICS antibody was the predominant one in patients with pemphigus (86% in skin and 80% in circulation). IgG4 anti-ICS antibody was seen in two thirds of specimens from pemphigus patients. IgG3 subclass antibody was more frequently seen in pemphigus than in bullous pemphigoid patients. Two-thirds of pemphigus sera were capable of activating complement in vitro. The complement binding activity was directly associated with IgG1 and/or IgG3 subclass antibodies. The possible mechanisms for the restricted IgG4 subclass antibodies in bullous pemphigoid and pemphigus are discussed.

Complement fixation by pemphigus antibody. V. Assembly of the membrane attack complex on cultured human keratinocytes

Previous studies have shown that pemphigus vulgaris (PV) IgG will fix early complement components (C1q, C4, and C3) to cultured murine epidermal cell surfaces and that PV IgG and complement alter epidermal cell membrane integrity. The present study was undertaken to determine if assembly of terminal complement components (C5, C6, C7, C8, and C9) and expression of C5b-9 neoantigens occur when PV IgG interacts with human keratinocyte (HuK) cell surface antigens in the presence of a source of complement. Monoclonal antibodies specific for C5, C6, C7, C8, C9, and C5b-9 neoantigens were screened for reactivity to the individual complement components in an assembled complex of human C5b-9 on rabbit red blood cell ghosts. Monoclonal antibodies (tissue culture supernatants) that bound to antigenic determinants accessible in the C5b-9 complex were selected for this study using immunofluorescence methods. HuK treated with PV IgG fixed C5, C6, C7, C8, C9, and C5b-9 neoantigens in a characteristic speckled pattern, while normal IgG did not. Heat inactivation or EDTA treatment of the complement source, or substitution of C2-depleted serum abolished C5, C6, C7, C8, C9, and C5b-9 neoantigen staining. PV IgG and complement also resulted in significant cytotoxicity to cell membranes as assessed using an ethidium bromide-fluorescein diacetate assay. These results suggest that PV IgG will activate the membrane attack complex of the complement system on HuK cell surfaces, resulting in cytotoxicity to cell membranes, further implicating complement in the pathogenesis of pemphigus.

Pemphigus

The term pemphigus refers to a group of autoimmune intraepidermal blistering diseases of the skin and mucous membranes. Several clinical variants of pemphigus are recognized. The major histologic feature of all variants is acantholysis, the disruption of normal cell-to-cell adhesion, which leads to intraepidermal blister formation. Most patients with pemphigus demonstrate IgG autoantibodies directed against an antigen located on the surface of keratinocytes. Although the stimulus for autoantibody production is unknown, several mechanisms have been proposed to explain the pathogenesis of acantholysis. One popular model proposes that pemphigus antibodies induce acantholysis through local stimulation of the plasminogen-plasmin system. Another model proposes that pemphigus antibodies fix complement and thereby alter cell membrane integrity to produce acantholysis. Prior to the availability of corticosteroids, pemphigus vulgaris was commonly fatal. Treatment with glucocorticosteroids has drastically improved the prognosis. Immunosuppressive agents and plasmapheresis have been used successfully in some patients with severe disease.

Subclass distribution of human IgG autoantibodies in pemphigus

The distribution of IgG subclasses in the intercellular substance (ICS) reactive autoantibodies in serum of 10 patients with pemphigus was analyzed by semiquantitative indirect immunofluorescence (IF) using the HP series of monoclonal antibodies specific for the four human IgG subclasses. IgG4 ICS specific autoantibody was present in all 10 sera at a titer of 10 to 320, while IgG1 antibodies were found in 9 of 10 sera at a seemingly lower level. IgG3 autoantibodies were detected in the serum of one patient, only after isolation of IgG using ion-exchange chromatography. Autoantibodies of IgG subclass 2 were not detectable in any of the 10 sera tested. One of the ten patients displayed circulating anti-ICS antibodies of only the IgG4 isotype.

Human pemphigus autoantibodies are pathogenic to squamous epithelium

In 1957, Witbesky et al. put forward several criteria that ideally should be fulfilled in order to prove the pathogenic role of an autoantibody in a putative autoimmune disease. There can now be very little doubt of the autoimmune nature of this disease and of the primary role of autoantibodies in its pathogenesis. The evidence that supports the concept that pemphigus autoantibodies are of primary pathogenic importance in the disease is as follows: IgG class autoantibodies can be found both circulating in the serum and bound to the epithelial cell surfaces in and around lesions in patients with pemphigus. These autoantibodies, purified from the serum of pemphigus patients, can induce acantholytic lesions typical of pemphigus both in experimental animals (neonatal mice) and in human and murine epidermal cell cultures. These autoantibodies react with a specific antigen of the epidermal cell. This purified antigen has been used to immunize rabbits and the resulting antibodies are capable of inducing pemphigus-like lesions in neonatal mice.

Complement in the pathophysiology and diagnosis of human diseases

Complement is a humoral effector system composed of 21 plasma proteins that was identified initially because of its cytolytic effects. In addition to cytolysis, complement has a number of different functions related to inflammatory and other host defense processes. The description of the reaction mechanism includes: (1) activation of the classical pathway through recognition of IgG and IgM antibodies by C1q, (2) activation of the alternative pathway which is usually achieved without participation of immunoglobulins, (3) generation of proteolytic enzymes composed of heteropolymers that cleave certain precursor proteins, (4) formation of the membrane attack complex (MAC), and (5) participation of control mechanisms. Methodologies for studying protein concentration and functional activities of complement components include not only the classical hemolytic techniques but also the extremely sensitive new radioimmunoassays and enzyme immunoassays for measuring the products of complement activation that are generated in vivo. Examples of genetically controlled complement deficiencies have been published for most complement components. The symptomatology of some of these patients serves to emphasize the protective role of complement. Acquired deficiencies are significant not only as laboratory aids in diagnosis and to evaluate the course of certain diseases, but also to indicate possible pathogenic disease mechanisms. Recently, it has been recognized that the complement proteins with genes located in the HLA region are polymorphic. Certain variants of proteins C2, C4, and factor B occur with higher frequencies in certain diseases than in the general population, which appears to be of great practical importance in laboratory medicine.

Complement fixation by pemphigus antibody. III. Altered epidermal cell membrane integrity mediated by pemphigus antibody and complement

The present study investigates the effects of pemphigus IgG and complement upon cell viability and/or membrane integrity using trypan blue exclusion, ethidium bromide (EB) staining, and fluorescein diacetate (FDA) conversion by living cells. Forty-eight-hour cultivated epidermal monolayers of neonatal BALB/c mice were incubated in media containing 1 mg/ml purified pemphigus IgG for 48 h in either the presence or absence of complement (absorbed AB sera). Adherent and detached cells were examined by both phase and fluorescence microscopy. Results from trypan blue exclusion showed that pemphigus IgG plus complement produced a modest decrease in exclusion of the dye compared to pemphigus IgG without complement. When FDA/EB comparisons were made, however, the differences were more substantial. When complement plus pemphigus IgG was added to cultures, the number of FDA-positive adherent cells decreased significantly and the number of EB-positive detached cells increased significantly. The effects of complement were inhibited by the use of heat-inactivated AB sera or by C1q depletion of AB sera. No significant effect on the cells was observed in the presence or absence of complement when pemphigus F(ab')2 fragments or when normal IgG was used. Plasminogen depletion of the complement source did not interfere with complement and pemphigus IgG effects as judged by the FDA/EB assay. These studies suggest that pemphigus antibody in the presence of complement alters cell membrane integrity and supports the contention that complement may play a significant role in the mechanism of acantholysis.

Immunopathologic mechanisms in pemphigus and bullous pemphigoid

Pemphigus and bullous pemphigoid are autoimmune bullous diseases of the skin. Pemphigus, an intraepidermal blistering disease, is characterized by autoantibodies reactive with antigens located in the intercellular spaces or on the surfaces of epidermal cells. These antibodies, which have recently been shown to activate complement, appear to be the cause of the basic pathologic process of pemphigus, acantholysis. The complement system and the plasminogen-plasmin system may be important mediators in the detachment of epidermal cells. Bullous pemphigoid, a subepidermal blistering disease, is characterized by autoantibodies reactive with an antigen located in the lamina lucida region of the basement membrane zone. These autoantibodies, which will avidly fix complement, appear to mediate subepidermal separation by attraction of a variety of inflammatory cells. Anaphylatoxins, released by activation of C4 and C3, or specific IgE antibodies, may activate mast cells with release of ECF-A attracting eosinophils. With activation of C5, C5a is released which could attract polymorphonuclear leukocytes. Antigen-specific lymphocytes, which can also contribute histamine releasing substances, may also be involved. The exact mechanism by which the epidermis separates from the dermis in bullous pemphigoid, however, remains unresolved.

Complement fixation by pemphigus antibody. I. In vitro fixation to organ and tissue culture skin

Although complement is often detected in the intercellular substance of pemphigus skin lesions, the ability of pemphigus antibodies to fix complement in vitro is controversial. The purpose of this study was to test in vitro complement fixation abilities of pemphigus antibodies further using organ and tissue culture methods. Epidermal cell monolayers from mouse tail were incubated with the purified IgG fraction of pemphigus serum followed by purified Clq. Binding of Clq, as well as IgG was demonstrated by immunofluorescence methods. When purified Clq was replaced with normal human serum as a complement source, positive C3 and C4 staining were also evident. When purified IgG of normal human serum was used in place of pemphigus IgG, similar immunofluorescence staining was not observed. Further evidence for complement fixation in vitro by pemphigus antibodies was obtained using organ cultures. Organ culture of normal human skin and monkey esophageal mucosa cultured in purified pemphigus IgG showed intercellular substance binding of IgG. No binding was observed when normal IgG was substituted for pemphigus IgG. Additional organ culture sections were then treated with complement (fresh normal human serum) and tested by in vitro complement staining. Fixation of Clq, C4, and C3 was noted in intercellular substance areas of organ cultured skin and mucosa incubated with pemphigus IgG but not those incubated with normal IgG. Prior treatment of pemphigus IgG organ cultured skin sections with unlabeled anti-C3, blocked positive C3 staining. These results suggest that some pemphigus antibodies are capable of activating complement in vitro.

Glucocorticosteroids and oral medicine

The article deals with the use of glucocorticosteroids in the treatment of the oral manifestations of Systemic Lupus Erythematosus (SLE), Discoid Lupus Erythematosus (DLE), Rheumatoid Arthritis (RA) in the temporomandibular joint, Pemphigus Vulgaris, Pemphigoid, Erythema Multiforme Exudativum (EME), Lichen Planus (LP), and Recurrent Aphthous Ulcerations (RAU). The benefit from steroids is discussed on the basis of current knowledge of etiology and pathogenesis of the various disorders. All of them are characterized by inflammation which appears secondary to a hypersensitivity reaction against autocomponents. Glucocorticoids do not interfere with the primary disease mechanisms. But it is concluded from the literature, that because of anti-inflammatory and immunosuppressive effects of the hormones, it seems reasonable to profit from steroids as palliatives in acute phases of the diseases and/or as long-term suppressors of the general host defense.

In vitro complement activation by intercellular antibodies

By in vitro complement immunofluorescence, 6 sera from pemphigus with intercellular antibodies were tested for their capability to fix C1q, C4, C3, and properdin. All 6 serum samples yielded positive reaction for C3 staining. Three serum samples gave positive staining for C1q, 5 serum samples for C4, and 3 serum samples for properdin, respectively. Substitution of C2 deficient serum as a complement source inhibited C3 and properdin staining but not positive C1q and C4 staining. These results are best explained by the concept that complement activation in vitro by intercellular antibodies occurs via the classical pathway followed by assembly of the C3 amplification mechanism.

Mechanism of lesion production in pemphigus and pemphigoid

Current evidence strongly supports the theory that the lesions of pemphigus are due to binding of pemphigus antibody to an antigen in or near the epidermal cell membrane, which causes a release of at least one enzyme which results in dissolution of the intercellular attachments and acantholysis. Similarly, strong evidence supports the hypothesis that pemphigoid blisters are due to binding of antibody at the basement membrane, followed by activation of complement and release of anaphylatoxins which activate tissue mast cells to release eosinophil chemotactic factor. These eosinophils then release tissue-destructive enzymes and reactive oxygen intermediates directly onto the basement membrane zone, with loss of dermoepidermal adherence and formation of blisters.

Experimental acantholysis by complement-fixing intercellular antibodies

Complement-fixing intercellular antibodies were detected in 10 of 17 sera from untreated pemphigus patients. The role of complement in the organ culture system was investigated using these sera. Ten sera possessing complement-fixing intercellular antibodies showed IgG binding to the intercellular substance in the organ-cultured skin and acantholysis-like changes were observed in eight cases. C3 deposition was not seen in any case. However, after treatment of the sections of cultured skin with fresh normal human serum, complement fixation of the intercellular substance by bound IgG was revealed in all the ten cases. No significant differences in the grade of acantholysis-like changes between the complement-depleted system and the complement-supplied system were observed. Complement does not appear to be necessary in the acantholytic process in the in vitro organ culture system, even though we considered the presence of complement-fixing intercellular antibodies.

Direct immunofluorescence on cytological smears in oral pemphigus

Direct immunofluorescence was performed on washed oral epithelial smears from thirteen patients with pemphigus vulgaris, thirteen patients with other oral diseases and from ten subjects with clinically healthy oral mucosa. The intercellular deposition of IgG was observed on cytological smears from oral smears from oral lesions in all patients with other oral diseases and from healthy controls, did not show any fluorescence. Therefore, direct immunofluorescence on cytological smears may be of value in the diagnosis of pemphigus.

Antibody-induced proteinase activation: a proposed mechanism for pemphigus

The current state of understanding of pemphigus includes the following: 1. Pemphigus is an autoimmune disease. In all variants a circulating autoantibody is found which binds to epidermal cells. In vivo antibody may be found deposited in the epidermis of patients. 2. The autoantibody levels generally correlate with disease activity indicating a relationship between antibody and clinical disease. 3. Although complement components are found in lesional skin, complement does not appear to be necessary for dissolution of the epidermal cement substance. 4. The treatment of pemphigus with corticosteroids has drastically reduced mortality rates. 5. Three different groups have presented results in two different experimental systems which indicate that subsequent to binding of pemphigus antibody to epidermal cells a proteinase is activated. This proteinase(s) degrades the intercellular cement substance of epidermis which results in loss of cellular adhesion and acantholysis. There are numerous questions still remaining. What is the nature of the proteinase(s) and the surface protein(s) it cleaves? Does the binding of pemphigus antibody to the cell surface induce enzyme synthesis, specific enzyme activation, or generalized lysosomal secretion? The answers to these questions will have broad biologic relevance since they may elucidate the role of anticell surface antibodies in disease states.

Pemphigus vulgaris and pemphigus foliaceus coexisting with oral lichen planus

Two women, aged 72 and 61 years, had mucocutaneous manifestations of pemphigus vulgaris, and one 76-year-old man had pemphigus foliaceus coexisting with oral lichen planus. Clinical and histopathological findings as well as direct and indirect immunofluorescence studies established the diagnosis.

Pemphigus antibody interaction with human epidermal cells in culture

The mechanism of pemphigus acantholysis has been studied with an in vitro system. Freshly prepared human skin epidermal cells were incubated in F-10 medium which contained the immunoglobulin G fraction from either pemphigus serum or normal human serum. During 18-h incubation periods, the pemphigus antibody became bound to the surface of the epidermal cells, caused the destruction of 75% of the viable cells as compared to only 14% in the normal immunoglobulin G controls (trypan blue exclusion), prevented the accumulation of newly synthesized proteins by nearly 60% as determined by radioactive tracer studies, and caused a dramatic shift in distribution of the newly synthesized proteins from an insoluble cell-associated fraction to an extracellular soluble fraction. These effects on the accumulation and partitioning of newly synthesized proteins were antibody concentration-dependent. Kinetic studies showed that at a fixed pemphigus antibody concentration the inhibition of protein accumulation preceded solubilization by about 1 h, at which time rapid solubilization of up to 70% of the insoluble cellular material occurred. Several lines of evidence suggested that this phenomenon was caused by enzymatic activity. Epidermal extracts solubilized a prepared substrate of radioactivity labeled insoluble epidermal cell material. This activity was heat labile and pH dependent, with pH optima ranging from 4.5 to 6.5. Enzymes with pH optima between 6 and 6.5 were recovered in the culture medium after a 2-day incubation of pure, intact epidermis with the pemphigus antibody. We proposed the following hypothesis to account for pemphigus acantholysis. The pemphigus antibody reacts with the epidermal cell surface and produces such a severe disturbance that the integrity of the cell surface is lost. As a result of these primary perturbations, the cell is killed and during the process, responds by release or activiation of soluble hydrolytic enzymes. This autolytic process results in the characteristic acantholysis of pemphigus.

Absence of intercellular antigens in the deep layers of the epidermis in pemphigus foliaceus

12 patients with pemphigus foliaceus, a form of pemphigus with lesions that arise in the intercellular substance in the superficial layers of the epidermis, and 7 patients with pemphigus vulgaris, where lesions are in the deep layers, were studied by immunofluorescence. Circulating antibodies to intercellular antigens (IC antibodies) were found in 11 pemphigus foliaceus and 5 pemphigus vulgaris patients. On direct immunofluorescence of skin lesions 75% (9 of 12), pemphigus foliaceus patients had intercellular deposits of IgG localized solely or predominantly in the superficial epidermal layers, whereas this was not the case in any of the patients with pemphigus vulgaris. Over 70% of the pemphigus foliaceus patients with predominantly superficial IgG deposits lacked in their lesions normal intercellular antigens usually expressed in the deep layers of the epidermis. This was shown by the inability of IC antibodies in autologous or allogeneic sera to bind to intercellular antigens in the lower epidermis of patient's skin, even though the same sera could bind to intercellular antigens in all layers of normal allogeneic skin. Lack of normal intercellular antigens deep in the epidermis may result in circulating IC antibodies binding to the superficial layers, a site which corresponds to, and thus in some patients may account for, the anatomical location of lesions in pemphigus foliaceus.

Capability of complement fixation of pemphigus antibodies in vitro

The capability of complement fixation of pemphigus antibodies was tested using combined in vitro complement immunofluorescent (IF) staining methods. Three sera out of 25 serum samples from 22 pemphigus patients revealed positive reactions, while all other sera gave negative results. Specificity control tests confirmed the positive reactions to be specific for complement staining. Complement fixing pemphigus antibodies were titrated lower than corresponding IgG antibodies and were demonstrable only in the extensive stage of the disease. Thus, the present work supplied evidence that pemphigus antibodies fix complement in vitro. However, the discrepancy still remains between the in vivo deposition of complement in most cases of pemphigus and in vitro capability of complement fixation in only few cases. More investigations should be needed to explain the exact role of complement in pemphigus acantholysis.

Experimental production of rabbit anti-guinea-pig epidermal cell sera. Comparison to pemphigus antibodies

Anti-epidermal cell sera (AES) were obtained by immunizing rabbits with enzymatically dispersed, viable guinea-pig epidermal cells followed by absorption with guinea-pig red blood cells, spleen and thymus cells, and liver powders. Complement-mediated cytotoxicity and immunofluorescence demonstrated that AES were towards cell surface antigen specific for stratified squamous epithelia of guinea pigs, and cross reacted with the corresponding tissues of humans and monkeys. Immunofluorescence revealed that AES reacted with Hassall's corpuscles and surrounding epithelial cells of the guinea-pig thympus which seemed to share common antigens with the epidermis; AES gave no reaction with other organs. While antigens reactive with pemphigus antibodies (PA) were demonstrated by membrane immunofluorescence to be present on the epidermal cell surface, PA showed no cytotoxicity to guinea-pig and human epidermal cells. Re-treatment of isolated epidermal cells with trypsin showed that antigens ractive with PA were more susceptible to the enzyme than those reactive with AES. These findings suggest that the cell surface antigens binding AES are different from the antigens which bind PA.

Autoimmune phenomena in ocular cicatricial pemphigoid

Twelve patients with various stages of ocular cicatricial pemphigoid were studied. Tear volumes measured by Schirmer tests and visual acuities were generally reduced in proportion to disease severity. Mannitol-positive staphylococcus was recovered from 67% (16/24) of the eyelids cultured. Immunoglobulins were bound to the basement membrane of clinically involved conjunctivae in 67% of the patients (8/12). Eighty percent (8/10) of the clinically normal conjunctivae had no immunoglobulins bound to the basement membrane or epithelium, further reinforcing the importance of tissue-fixed immunoglobulins in the pathogenesis of this condition. Four of eight patients with immunoglobulins bound to basement membrane also had C3 complement bound to basement membrane. Acute disease may be associated with the presence of complement in the conjunctiva. In addition, three of the eight patients with basement membrane staining, and three without, showed marked epithelial intercellular and intracellular staining for immunoglobulins. Indirect immunofluorescence of patients' sera showed no circulating antibodies to basement membrane, but three patients had circulating antibodies directed to the conjunctival epithelium in an intercellular or intracellular location. No significant association of ocular pemphigoid with other circulating autoantibodies. HLA aantigens, or abnormal serum immunoglobulin levels was realized.