Antibodies against keratinocyte antigens other than desmogleins 1 and 3 can induce pemphigus vulgaris-like lesions

Pemphigus is an autoimmune disease of skin adhesion associated with autoantibodies against a number of keratinocyte antigens, such as the adhesion molecules desmoglein (Dsg) 1 and 3 and acetylcholine receptors. The notion that anti-Dsg antibodies alone are responsible for blisters in patients with pemphigus vulgaris (PV) stems from the ability of rDsg1 and rDsg3 to absorb antibodies that cause PV-like skin blisters in neonatal mice. Here, we demonstrate that PV IgGs eluted from rDsg1-Ig-His and rDsg3-Ig-His show similar antigenic profiles, including the 38-, 43-, 115-, and 190-kDa keratinocyte proteins and a non-Dsg 3 130-kDa polypeptide present in keratinocytes from Dsg 3 knockout mouse. We injected into Dsg 3-lacking mice the PV IgGs that did not cross-react with the 160-kDa Dsg 1 or its 45-kDa immunoreactive fragment and that showed no reactivity with recombinant Dsg 1. We used both the Dsg3(null) mice with a targeted mutation of the Dsg3 gene and the "balding" Dsg3(bal)/Dsg3(bal) mice that carry a spontaneous null mutation in Dsg3. These PV IgGs caused gross skin blisters with PV-like suprabasal acantholysis and stained perilesional epidermis in a fishnet-like pattern, indicating that the PV phenotype can be induced without anti-Dsg 3 antibody. The anti-Dsg 1 antibody also was not required, as its presence in PV IgG does not alter the PV-like phenotype in skin organ cultures and because pemphigus foliaceus IgGs produce a distinct phenotype in Dsg3(null) mice. Therefore, mucocutaneous lesions in PV patients could be caused by non-Dsg antibodies.

[Detection of circulating pemphigus vulgaris antibodies in families of patients with pemphigus vulgaris]

OBJECTIVE

To detect the autoantibodies on 30 first-degree relatives of 12 patients with pemphigus vulgaris (PV), who may share the same susceptible gene with the patients.

METHODS

Immunoblot and indirect immunofluorescence (IIF) method were used to detect circulatory PV antibodies in the peripheral blood.

RESULTS

PV antibodies were found in 19 of 30 (63%) relatives by both methods, but 10 control serum were all negative by both methods.

CONCLUSION

Healthy PV antibody carriers may also exist in high frequency in the first-degree relatives of Chinese PV patients.

HLA class II allele associations in Korean patients with pemphigus

BACKGROUND

Studies at the population level have demonstrated associations between pemphigus (pemphigus vulgaris, PV, and pemphigus foliaceus, PF) and particular HLA haplotypes, which suggests that there may be a genetic predisposition for the disease.

OBJECTIVE/METHODS

The aim of the present study was to examine the distribution/frequency pattern of HLA class II alleles (DRB1, DQA1 and DQB1) from a group of 30 Korean patients with pemphigus (15 PV and 15 PF) by PCR amplification with sequence-specific primers.

RESULTS

In PV, the frequency of DRB1*01 allele was found to be significantly high (pc = 0.0014); in PF, DRB1*01, DQA1*0302 and DQB1*0603 alleles showed positive associations with statistical significances (pc = 0.0002, 0.0007 and 0.0067, respectively), when compared with those found in Korean controls.

CONCLUSIONS

In this small-sample study, findings of allelic frequencies among Korean patients with pemphigus are somewhat different from those found in other populations.

The distribution of pemphigus vulgaris-IgG subclasses and their reactivity with desmoglein 3 and 1 in pemphigus patients and their first-degree relatives

BACKGROUND

Pemphigus vulgaris (PV) autoantibodies (PV-IgG) have been found in 40-70% of sera of first-degree relatives of pemphigus patients.

OBJECTIVES

To determine the possible role of PV-IgG subclasses in the pathogenesis of the disease.

PATIENTS AND METHODS

Study groups comprised 25 PV patients, 55 unaffected family members and 56 sera of healthy individuals. Indirect immunofluorescence (IIF) staining and Western immunoblotting (WB) techniques were used to determine total PV-IgG and PV-IgG subclasses and their reactivity to desmoglein (Dsg) 1 and 3.

RESULTS

By IIF staining, circulating PV-IgG were found in 64% of the patients, in 15% of the relatives and in none of the controls (P < or = 0.001); by WB the results were 91%, 49% and 12%, respectively (P < or = 0.001). The distribution of PV-IgG subclasses 1-3 was similar among patients and their relatives. PV-IgG4 was found in 62% of the patients but in only one relative and was absent in the controls (P < or = 0.001). PV-IgG1, 2 and 4 were found to react mainly with Dsg3 and PV-IgG3 mainly with Dsg1 and 3.

CONCLUSIONS

These results support the concept of a genetic predisposition in pemphigus. The non-complement-fixing PV-IgG4 and at least one complement-fixing PV-IgG subclass appear to be involved in the pathogenesis of the disease. The absence of PV-IgG4 among relatives who were PV-IgG carriers seems to be linked to the fact that they do not develop pemphigus. The exact nature of this linkage is still unclear.

HLA class II polymorphism contributes to specify desmoglein derived peptides in pemphigus vulgaris and pemphigus foliaceus

Susceptibility to Pemphigus, an autoimmune disease of the skin, has been previously linked to DRB1*0402, 1401/04 and DQB1*0503 in pemphigus vulgaris (PV), to DRB1*0102, 0404, 1402/06 in endemic pemphigus foliaceus in Brazil and to DRB1*04 in Italian patients suffering from pemphigus foliaceus (PF). The disease is caused by autoantibodies against desmoglein (Dsg1 in PF, Dsg3 in PV). Molecular typing of 57 French patients suffering from PV (37) and from PF (20) confirmed previous results concerning PV and showed that DRB1*0102 and 0404 are susceptible molecules to PF in France. We have analysed the characteristics of the 'pockets' of the susceptibility-associated molecules to PV and PF and we showed that (i) in PV, two kinds of Dsg3 derived peptides may be presented by HLA-DR according to HLA polymorphism (DRB1*0402 or DRB1*14/0406), (ii) the same Dsg1 peptides may be presented by DRB1*0102, DQB1*0404 or DRB1*14 in PF, (iii) the DRB1*14/0406 PV-related molecules may be able to present Dsg1 and Dsg3 peptides thereby providing an explanation for the cases of PV with combined responses to Dsg1 and to Dsg3 which are typified by a muco-cutaneous clinical phenotype.

Subcorneal pustular dermatosis type of IgA pemphigus: demonstration of autoantibodies to desmocollin-1 and clinical review

We describe a 40-year-old Japanese man with a 3-year history of vesiculopustular lesions resembling subcorneal pustular dermatosis. Histopathology showed subcorneal pustules containing a few acantholytic cells, and direct immunofluorescence disclosed IgA deposition in the intercellular space of the upper epidermis. Circulating IgA autoantibodies of very low titre were also demonstrated by indirect immunofluorescence. A novel cDNA transfection technique clearly detected IgA autoantibodies reactive with human desmocollin-1. Combined therapy with dapsone and etretinate improved the skin lesions. We review the clinical features of 49 patients in the literature who presented with vesiculopustular lesions and intraepidermal IgA deposition.

Immune modulation in pemphigus vulgaris: role of CD28 and IL-10

Pemphigus vulgaris (PV) is an autoimmune bullous skin disease characterized by Abs to the desmosomal cadherin desmoglein-3. Although the autoantibodies have been shown to be pathogenic, the role of the cellular immune system in the pathology of pemphigus-induced acantholysis is unclear. To further delineate the potential role of T cell-signaling pathways in the pathogenesis of PV, we performed passive transfer experiments with PV IgG in gene-targeted mutant mice. Our results demonstrated that CD28-deficient mice (lacking a costimulatory signal for T cell activation) are 5-fold more sensitive to the development of PV than wild-type mice. To evaluate whether the higher incidence of disease was due to an impairment in intercellular adhesion of keratinocytes, we performed an in vitro acantholysis, using CD28-/- mice keratinocytes. No alteration in in vitro adhesion was detected in CD28-/--type keratinocytes. Because the CD28 molecule plays a pivotal role in the induction of Th2 cytokines, we examined the levels of a prototypic Th2 cytokine (IL-10) in CD28-/- mice. Lower levels of IL-10 mRNA were found in lesions from CD28-/- mice. To determine whether pemphigus susceptibility in CD28-/- was related to IL-10 deficiency, we performed passive transfer experiments in IL-10-/- mice that demonstrated increased blisters compared with controls. To confirm that IL-10 is involved in the pathogenesis, rIL-10 was given with PV IgG. IL-10 significantly suppressed the disease activity. These data suggest a potential role of IL-10 in PV.

HLA-DRB1 polymorphisms and autoimmune responses to desmogleins in Japanese patients with pemphigus

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are caused by autoantibodies against keratinocyte adhesion molecules desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1), respectively. To determine possible major histocompatibility complex (MHC) class II associations with autoantibody responses to desmogleins, haplotype and allele distributions, along with molecular polymorphisms of HLA-DR and -DQ genes were analyzed based on the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) results in 85 Japanese patients with pemphigus. Each of 55 PV patients carried at least one allele of HLA-DRB1*04 and DRB1*14 subtypes, with significant increases of HLA-DRB1*0406/DQA1*0301/DQB1*0302, DRB1*14/DQA1*0104/DQB1*05 and DRB1*1406/DQA1*0503/ DQB1*0301 haplotypes compared to normal controls. The HLA-DRB1*04 and DRB*14 alleles carried by PV patients shared hydrophobic amino acid residues Phe26, Leu67 and Val86, as well as hydrophilic amino acid residues at positions 70 and 71 on the DRB1 beta chain. HLA-DR/DQ distributions did not differ among PV patients according to the presence or absence of anti-Dsg1 co-existing with anti-Dsg3. Thirty PF patients, all producing autoantibodies only to Dsg1, showed more diverse HLA-DR/DQ distributions, sharing hydrophobic amino acid residues at positions 26 and 67, as well as hydrophilic amino acid residues at positions 70 and 71, of the DRB1 chain. These findings suggest that autoantibody responses to desmogleins might be regulated by amino acid residues at positions 26, 67, 70, 71 and 86 at peptide binding sites of HLA-DRB1 molecules, and that autoimmune responses to Dsg3 might be more strictly regulated by specific amino acid residues at these positions on the HLA-DRB1 chain than responses to Dsg1.

Human desmocollin 1a transiently expressed in COS-7 cells and NIH 3T3-3 cells is reacted by IgG4 antibodies in a pemphigus foliaceus serum

Human desmocollin (Dsc) 1 is an autoantigen in the subcorneal pustular dermatosis type of IgA pemphigus. Moreover, Dscs, particularly bovine Dscs, are recognized by IgG antibodies in certain sera of various types of pemphigus by immunoblotting. In this study, 10 pemphigus sera were examined by immunofluorescence for IgG antibodies to human Dsc1a, Dsc2a and Dsc3a transiently expressed in COS-7 and NIH 3T3-3 cells using two different transfection methods. IgG antibodies in a number of sera showed a strong background staining with untransfected COS-7 and NIH 3T3-3 cells. Using COS-7 cells, a pemphigus foliaceus serum, which did not stain untransfected COS-7 cells, was found to contain IgG antibodies reactive exclusively with Dsc1a. This serum showed the same reactivity in studies using NIH 3T3-3 cells. Moreover, this pemphigus foliaceus serum contained IgG4, but not IgG1 antibodies, to Dscla expressed in the NIH 3T3-3 cells. These results indicate that autoantibody response in pemphigus foliaceus might be more heterogenous than hitherto supposed.

Common human leukocyte antigen alleles in pemphigus vulgaris and pemphigus foliaceus Italian patients

Pemphigus refers to a group of autoimmune blistering skin diseases, mainly identified as pemphigus vulgaris and pemphigus foliaceus, both characterized by the presence of autoantibodies against keratinocyte adhesion molecules, leading to loss of cell-cell adhesion with consequent blister formation. Pemphigus vulgaris is reported to be associated with human leukocyte antigen DR4 and/or DR6 whereas no data are available on pemphigus foliaceus, except for the endemic Brazilian form (fogo selvagem), which is reported to be associated with DR1 and DR4. We here report human leukocyte antigen molecular typing on a total of 87 patients, 61 with pemphigus vulgaris and 26 with pemphigus foliaceus, versus 128 healthy matched controls. Generic typing showed an increase of DRB1*04 and DRB1*14 and a decrease of DRB1*07 in both pemphigus vulgaris and pemphigus foliaceus patients. Molecular subtyping of DR4+ and DR14+ subjects showed a highly significant association between the DRB1*1401 and both pemphigus vulgaris (p < 0.0001) and pemphigus foliaceus patients (p < 0.0001) together with a significant increase of the linked DQB1*0503 (pemphigus vulgaris p < 0.0001; pemphigus foliaceus p < 0.0001). Moreover, whereas the association between DRB1*0402 and pemphigus vulgaris (p < 0.0001) has been confirmed, no significant association between a specific allele of the DR4 group and pemphigus foliaceus, has been found. Therefore, at least in Italian patients, pemphigus vulgaris and pemphigus foliaceus share DRB1*1401 and DQB1*0503, as susceptible human leukocyte antigen alleles, whereas DRB1*0402 is only found associated with pemphigus vulgaris. The observation that both diseases, pemphigus vulgaris and pemphigus foliaceus, carry the same susceptible human leukocyte antigen alleles has been interpreted as a common genetic background predisposing to pemphigus as, like in other autoimmune disorders, it is not sufficient to explain the onset of the disease on the basis of the sole aforementioned alleles. Other linked genes and/or environmental factors should play a facilitating role in the outbreak of pemphigus, either pemphigus vulgaris or pemphigus foliaceus.

[PCR determination of an association between class II HLA and pemphigus vulgaris]

Pemphigus vulgaris (PV) is an autoimmune blistering disease affecting the skin and mucous membranes. It is characterized by the presence of an autoantibody directed against desmoglein 3, which causes acantholysis and blister formation. In this study, we examined the HLA antigens of 30 caucasian argentinian patients compared with 199 controls. We used the PCR-SSO method (Polymerase Chain Reaction-Sequence Specific Oligonucleotide). We found that PV patients had significantly increased frequencies of HLA DR4 (RR = 3.80, P = 0.001) and HLA DR 14 (RR = 5.97, P = 0.0001). As in other populations, two associated alleles were found: the first was DR beta 1*0402 (RR = 44.70, P = 10.7) and DQ beta 1*0302 (RR = 71.82, P = 10(-7)) and the second was DR beta 1*1401 (RR = 117.94, P = 10(-7)) y DQ beta 1*0503 (RR = 86.95, P = 10(-7)).

Three different autoimmune bullous diseases in one family: is there a common genetic base?

We report an unusual familial occurrence of autoimmune bullous diseases. Three members of a family suffered from three different autoimmune bullous diseases: pemphigus vulgaris (PV), linear IgA disease (LAD) and cicatricial pemphigoid (CP). The HLA type was determined in five family members: all were positive for HLA-DQ5/DR6, which is reported to be associated with susceptibility to PV. The CP patient was DQ7(3) positive, which is in concordance with enhanced susceptibility to ocular CP and CP. The LAD patient was B8 and DR3 negative but positive for HLA-A1. Our study supports the hypothesis that there is a genetically transmitted susceptibility to autoimmune bullous diseases but that additional factors seem necessary actually to develop a particular disease.

Distribution of HLA class II alleles among Spanish patients with pemphigus vulgaris

Twenty-six unrelated Spanish Caucasian individuals affected by pemphigus vulgaris (PV) were HLA typed and frequencies compared with those of 200 ethnically matched healthy controls. Twenty-three out of 26 patients were HLA-DR4. The frequency of HLA-DR14 was also increased (31%; controls: 4%). Of the 23 patients positive for HLA-DR4, 21 carried the DRB1*0402 allele. Therefore, the frequency of HLA-DRB1*0402 among patients was 81% (4% in controls; P=4.7x10(-27), OR=100.8). Interestingly, HLA-DR13, a frequent HLA-DR specificity in the Spanish general population (27%), was absent among the PV patients (P=0.009; Pc=0.1; OR=0.05). Taking together these data, we can conclude that, in the Spanish population, PV is preferentially and strongly associated with HLA-DRB1*0402, whereas DRB1*13 seems to confer a protective effect in our population.

Desmoglein 3 anchors telogen hair in the follicle

Little is known about the function of desmosomes in the normal structure and function of hair. Therefore, it was surprising that mice without desmoglein 3 (the autoantigen in pemphigus vulgaris) not only developed mucous membrane and skin lesions like pemphigus patients, but also developed hair loss. Analysis of this phenotype indicated that hair was normal through the first growth phase (‘follicular neogenesis’). Around day 20, however, when the hair follicles entered the resting phase of the hair growth cycle (telogen), mice with a targeted disruption of the desmoglein 3 gene (DSG3-/-) lost hair in a wave-like pattern from the head to the tail. Hair then regrew and was lost again in the same pattern with the next synchronous hair cycle. In adults, hair was lost in patches. Gentle hair pulls with adhesive tape showed that anagen (growing) hairs were firmly anchored in DSG3-/- mice, but telogen hairs came out in clumps compared to that of DSG3+/− and +/+ littermates in which telogen hairs were firmly anchored. Histology of bald skin areas in DSG3-/- mice showed cystic telogen hair follicles without hair shafts. Histology of hair follicles in early telogen, just before clinical hair loss occurred, showed loss of cell adhesion (acantholysis) between the cells surrounding the telogen club and the basal layer of the outer root sheath epithelium. Electron microscopy revealed ‘half-desmosomes’ at the plasma membranes of acantholytic cells. Similar acantholytic histology and ultrastructural findings have been previously reported in skin and mucous membrane lesions of DSG3-/- mice and pemphigus vulgaris patients. Immunoperoxidase staining with an antibody raised against mouse desmoglein 3 showed intense staining on the cell surface of keratinocytes surrounding the telogen hair club in normal mice. Similar staining was seen in human telogen hair with an anti-human desmoglein 3 antibody. Finally, a scalp biopsy from a pemphigus vulgaris patient showed empty telogen hair follicles. These data demonstrate that desmoglein 3 is not only critical for cell adhesion in the deep stratified squamous epithelium, but also for anchoring the telogen hair to the outer root sheath of the follicle and underscore the importance of desmosomes in maintaining the normal structure and function of hair.

Polymorphisms of HLA class II genes in Japanese patients with pemphigus vulgaris

Pemphigus vulgaris (PV) is an autoimmune disease mediated by autoantibodies that bind to a keratinocyte adhesion molecule, desmoglein-3. The purpose of this study was to identify critical amino acid residues of PV-associated HLA class II genes. Haplotype and allele distributions, along with molecular polymorphisms, of HLA class II genes were analyzed based on the polymerase chain reaction-restriction fragment length polymorphism in 17 Japanese PV patients. Each patient had one or two alleles of DRB1*04 (*0403, *0404, *0406) or DRB1*14 (*1401, *1405, *1406) subtypes. All DRB1*04 and DRB1*14 alleles carried by PV patients with different ethnic backgrounds reported to date, including DRB1*0402, which confers strong susceptibility to PV among Jewish populations, have amino acid residues Phe26, Leu67 or Ile67, and Val86, as well as hydrophilic amino acid residues at positions 70 and 71 of the DRB1 beta chain.

HLA-DRB1*04 and DRB1*14 alleles are associated with susceptibility to pemphigus among Japanese

It has previously been demonstrated that susceptibility to pemphigus vulgaris is associated with human leukocyte antigen (HLA)-DR4 serologic specificity among Ashkenase Jews, and with DR4 as well as DR6 (DR14) in other ethnic groups. We genotyped HLA-DRB1, DQA1, DQB1, and DPB1 alleles in 16 patients with pemphigus by polymerase chain reaction-restriction fragment length polymorphism, to find evidence of potential HLA class II allele associations with pemphigus in Japanese patients who have a relatively homogeneous ethnic background. All nine patients with pemphigus vulgaris and five of seven patients with pemphigus foliaceus carried one or two alleles of HLA-DRB1*04 (*0403, *0406) and HLA-DRB1*14 (*1401, *1405, *1406) subtypes. Sequence analysis of these DRB1*04 and DRB1*14 alleles revealed the amino acid homology of phenylalanine at position 26 and valine at position 86 with the DRB1*0402 allele that reportedly confers a strong susceptibility to pemphigus vulgaris in Ashkenazi Jews. Thus our findings, together with previous HLA studies on pemphigus vulgaris patients of different ethnic groups, suggest that HLA-DRB1*04 and DRB1*14 alleles are commonly associated with pemphigus vulgaris across racial barriers. These HLA-DRB1 alleles are likely to be also associated with pemphigus foliaceus. Further studies on more diverse ethnic populations will be helpful in determining the significance of the association between certain amino acid residues of the class II molecules and disease susceptibility to pemphigus vulgaris as well as pemphigus foliaceus.

Pemphigus vulgaris autoantibody response is linked to HLA-DQB1*0503 in Pakistani patients

Pemphigus vulgaris (PV) is an autoimmune disease of the skin and mucous membranes characterized by an autoantibody response against an epidermal cadherin. We performed high resolution HLA class II typing in 19 patients with PV from Rawalpindi, Pakistan and 19 non-Jewish European PV patients from Boston by sequence-specific oligonucleotide probe hybridization. The results were compared with two separate ethnically matched control populations. WE found that PV patients from Pakistan had significantly increased frequencies of DRB1*1404 (p = 0.01), DQA1*0101 (p = 0.02), and DQB1*0503 (p = 0.01). Among the patients of non-Jewish European ancestry, DRB1*1401 (p < 10(-6)), DQA1*0101 (p < 10(-5)) and DQB1*0503 (p < 10(-6)), were increased in PV patients. Formal linkage analysis between the major histocompatibility complex and the PV antibody was performed in 67 relatives of the 19 Pakistani patients. The results showed strong evidence for linkage of HLA-DRB1*1404, DQA1*0101, DQB1*0503, with the presence of PV antibody in relatives' families with a significant logarithm of the odds score of 6.06. Based on the three dimensional structure of class II molecules, we propose that HLA-DQA1*0101 and DQB1*0503, encode a negatively charged P9 peptide binding pocket of the DQ molecule and are significantly associated with susceptibility to PV in non-Jewish populations.

Identical MHC markers in non-Jewish Iranian and Ashkenazi Jewish patients with pemphigus vulgaris: possible common central Asian ancestral origin

Previous studies showed that almost all Ashkenazi Jewish patients with pemphigus vulgaris carried the extended haplotype [HLA-B38, SC21, DRB1*0402, DQB1*0302] or [HLA-B35, SC31, DRB1*0402, DQB1*0302] or class II fragments of them. Non-Jewish patients carried [HLA-B55, SB45, DRB1*1401, DQB1*0503] or its class II fragments. In the present study of 20 Iranian patients with pemphigus vulgaris, 17 were found to carry DRB1*0402, DQB1*0302 haplotypes, also found among normal Iranian haplotypes and the same as that of the Jews. These findings suggest that the pemphigus MHC susceptibility gene among Iranians derived from the same ancestor as that in the Ashkenazim. The ancient Jews were under Persian domination from 500 B.C. until 300 B.C. and in the 8th century A.D., a Tataric people living in the kingdom of Khazar on the Western shore of the Caspian Sea and the Northern shore of the Black Sea, near Persia, converted to Judaism, providing possible opportunities for gene mixing in two populations that are distinct and separate today.

Vesicle formation and follicular root sheath separation in mice homozygous for deleterious alleles at the balding (bal) locus

The balding (bal) mutation of the mouse is an autosomal recessive mutation that causes alopecia and immunologic anomalies. A new allele was identified by allelism testing after using an interspecific backcross to localize the mutation to the centromeric end of mouse chromosome 18. We investigated the skin and hair histologic lesions of two alleles (bal(J) and bal(Pas)) at this locus and analyzed the expression of several keratinocyte markers and the production of autoantibodies by immunofluorescence on frozen skin sections. The lesions observed included separation of the inner and outer root sheath in anagen follicles resulting in the hair fiber being very easily plucked from the follicle. Vesicles on the ventral tongue, mucocutaneous junction of the eyelid, foot pads, and rarely in skin were also evident. Separation occurred between the basal and suprabasilar cells forming an empty cleft, resembling that observed in human pemphigus vulgaris. Immunofluorescence studies did not reveal the presence of tissue-bound or circulating autoantibodies. Expression of keratinocyte markers in hair follicles was normal. Keratin 6-positive cells were found on either side of the follicular separation suggesting a molecular defect in adhesion molecules between the inner layer of the outer root sheath cells to layers on either sides. This hypothesis has been confirmed by another group who demonstrated that the bal(J) mutation is due to the insertion of a thymidine in the desmoglein 3 gene, resulting in a premature stop codon.

Circulating pemphigus IgG in families of patients with pemphigus: comparison of indirect immunofluorescence, direct immunofluorescence, and immunoblotting

BACKGROUND

Patients with pemphigus vulgaris (PV) are genetically linked to two alleles of the HLA subgroup, and circulating antibodies were found in first-degree relatives of these patients, thus showing genetic predisposition.

OBJECTIVE

Our purpose was to determine the occurrence of circulating true PV-IgG in patients' relatives.

METHODS

Circulating PV-IgG was determined in 21 first-degree relatives of 12 patients with PV by indirect immunofluorescence on monkey esophagus, carcinoma A431 cultures, and Western immunoblotting. Direct immunofluorescence was performed on skin biopsy specimens of 20 relatives.

RESULTS

Circulating PV-IgG was detected in 15 relatives (71%) by all methods tested. Good correlation was found between immunoblot reactivity and immunofluorescence. Of the 15 "positive" relatives, only five showed fixation of IgG to epidermal cells in vivo.

CONCLUSION

The permeability of the epidermis or epidermal cell reactivity in vivo probably controls the expression of disease in patients' relatives.

An epitope in the third hypervariable region of the DRB1 gene is involved in the susceptibility to endemic pemphigus foliaceus (fogo selvagem) in three different Brazilian populations

Endemic pemphigus foliaceus or fogo selvagem (FS) in an organ-specific autoimmune skin disease characterized by epidermal vesicles and mediated by autoantibodies. Family cases are frequent and not everyone living in endemic region develops FS suggesting that host factors play a role in determining whether exposed individuals will be affected. Because our previous works with Brazilian Mestizos and with Xavante Indians have shown that particular HLA alleles confer increased risk for the disease, we decided to extend these studies to another homogeneous population, the Terena Indians. 19 out of 20 Terena patients were either positive for DRB1*0404, 1402 or 1406 (p < 0.005, RR = 14). These findings were in agreement with the data obtained from the Xavante study. In Mestizos the association was with DRB1*01. All these alleles involved in predisposition to the disease in different populations shared the same amino acid sequence at position 67-74 on the third hypervariable region of the DRB1 gene: LLEQRRAA, suggesting that inheritance of this sequence is involved in the susceptibility to FS. When patients and controls data from different studies were pooled and analyzed disregarding the ethnic background and the HLA alleles involved, the results obtained clearly supported the hypothesis that matching for this epitope is highly significant and predictive of FS predisposition (p < 0.00001, RR = 6.4).

Cloning of the gene for human pemphigus vulgaris antigen (desmoglein 3), a desmosomal cadherin. Characterization of the promoter region and identification of a keratinocyte-specific cis-element

Pemphigus vulgaris antigen is a cadherin-like desmosomal cell adhesion molecule expressed primarily in suprabasal keratinocytes within the epidermis. Previously characterized structural features have defined this molecule as a desmoglein, DSG3. In this study, we have cloned the human DSG3 gene and examined the transcriptional regulation of its expression. The total gene consisted of 15 exons and was estimated to span >23 kilobases. Comparison of exon-intron organization of DSG3 with bovine DSG1 and several classical cadherin genes revealed striking conservation of the structure. Up to 2.8 kilobases of the upstream genomic sequences were sequenced and found to contain several putative cis-regulatory elements. The promoter region was GC-rich and TATA-less, similar to previously characterized mammalian cadherin promoters. The putative promoter region was subcloned into a vector containing chloramphenicol acetyl transferase reporter gene. Transient transfections with a series of deletion clones indicated that the DSG3 promoter demonstrated keratinocyte-specific expression, as compared with dermal fibroblasts examined in parallel, and fine mapping identified a 30-base pair segment at -200 to -170 capable of conferring epidermal specific expression. The results provide evidence for the transcriptional regulation of the pemphigus vulgaris antigen gene, potentially critical for development of the epidermis and physiologic terminal differentiation of keratinocytes.