The melanocortin (MC3) receptor from rat hypothalamus: photoaffinity labelling and binding of alanine-substituted alpha-MSH analogues

Membrane preparations of cells expressing the cloned rat hypothalamus melanocortin receptor, MC3, have been photoaffinity labelled using a radiolabelled photoreactive analogue of alpha-MSH, [125I-Tyr2,Nle4,D-Phe7,ATB-Lys11]alpha-MSH. SDS-PAGE followed by autoradiography showed a single band at 53-56 kDa for the native receptor or 35 kDa after deglycosylated with PNGase F, consistent with the predicted cDNA sequence. Receptor binding studies with alpha-MSH, gamma-MSH and [Nle4,D-Phe7]alpha-MSH established that alpha-MSH and gamma-MSH had similar affinities while [Nle4,D-Phe7]alpha-MSH bound 100 times more strongly. These results suggest that the receptor recognises the conserved 'core sequence' (-Met-Glu/Gly-His-Phe-Arg-Trp-) of MSH/ACTH peptides. The binding affinities of alanine-substituted analogues of alpha-MSH were determined to investigate the role of individual residues in ligand-receptor interactions. While in the terminal regions only the replacement of Tyr2 reduced the affinity of the peptide, replacement of Met4, Phe7, Arg8 and Trp9 within the peptide core led to a significant loss of affinity. Glu5 appeared unimportant for receptor recognition.

Common major histocompatibility complex class II markers in clinical variants of cicatricial pemphigoid

Cicatricial pemphigoid (CP) is a chronic autoimmune blistering disease affecting multiple mucous membranes derived from stratified squamous epithelium and occasionally the skin. CP has a wide spectrum of disease manifestations. Patients with oral pemphigoid (OP) have a benign self-limited disease in which pathological changes are restricted to the oral mucosa. On the other hand, patients with ocular cicatricial pemphigoid (OCP), a chronic condition marked with relapses and remissions, have ocular involvement and also perhaps involvement of other mucous membranes. All clinical subsets are characterized by the presence of a similar anti-basement zone autoantibody. The factors that determine the development of one form of CP or the other are not known. In a previous study, we described the association between OCP and the DQB1*0301 allele (P = 0.006). In this study, we have analyzed 22 Caucasian patients with OP and their family members for major histocompatibility complex DRB generic, DQA1, and DQB1 allele associations by PCR-sequence-specific oligonucleotide probe hybridization. The results were compared to those obtained from 17 Caucasian patients with OCP and to control Caucasian alleles and haplotypes. The DQB1*0301 allele frequency was 38.6% in OP, 52.9% in OCP, and 17.8% in controls. Statistically significant associations were detected between the DQB1*0301 allele and both OP (P = 0.0047) and OCP (P < 0.0001). In addition, DRB1*04 showed a statistically significant association (P = 0.005) with OCP when compared to controls. Analysis of major histocompatibility complex class II haplotypes showed significant statistical associations between both OCP and OP and the HLA-DRB1*04, DRB4*0101, DQA1*03, DQB1*0301 haplotype (P < 0.0001 and P = 0.0012, respectively). Our results indicate that DQB1*0301 is a marker of both oral and ocular forms of CP. The analysis of the amino acid sequence of the DQB1 alleles present in both OP and OCP suggested that amino acid residues at position 57 and positions 71-77 may also be markers of CP.

Correlation of subclasses of IgG with disease activity in pemphigus vulgaris

Pemphigus vulgaris is an autoimmune blistering disease that is characterized by the presence of an antibody against an epidermal cell protein. In our previous studies, we have demonstrated that the presence of the antibody in the patients and in the healthy relatives of the patients strongly correlates with MHC haplotypes. The purpose of this study was to determine the subclasses of IgG present in the sera of patients with active disease, those in remission, healthy and unaffected relatives and normal controls. The presence of the autoantibody to the pemphigus antigen was assayed by a modified, sensitive immunoblot technique. The assay was considered positive if a 130-kD band was seen when normal human epidermis was used as a substrate. In patients with active disease, the sera contained antibodies of the IgG1 and IgG4 subclasses. The sera of patients in remission, those of healthy unaffected relatives and normal controls contained only the IgG1 subclass. The normal controls consist of MHC-matched and nonmatched individuals. This study indicates that patients with disease activity have an antibody which is of the IgG1 and IgG4 subclasses, which we consider to be a pathogenic antibody. The sera of healthy relatives and normal controls that contain an antibody which binds to the pemphigus antigen is of the IgG1 subclass only and is considered to be a nonpathogenic or natural autoantibody. These observations provide the basis to study the immunoregulatory mechanisms and the production of normal and pathogenic antibodies.

Solubilisation partial characterisation of the alpha-MSH receptor on primary rat Schwann cells

The ACTH/MSH melanocortin core peptide sequence possesses neurotrophic properties in peripheral nerve. During functional neuroanatomical recovery after damage to peripheral nerves, Schwann cells play a significant role in facilitating regeneration. Here we employ a modified super-potent alpha-MSH analogue to solubilise alpha-MSH receptor proteins from cultured primary rat Schwann cells. [125I-Tyr2,Nle4,D-Phe7,ATB-Lys11]-alpha-MSH photoaffinity labelled proteins from Schwann cells were analyzed by SDS-PAGE followed by autoradiography. The results indicate that the alpha-MSH receptor proteins labelled have a molecular weight of 42-45 kDa. These data are the first to demonstrate solubilisation and characterisation of alpha-MSH receptors from non-melanoma cells.

Major histocompatibility complex susceptibility genes for dermatitis herpetiformis compared with those for gluten-sensitive enteropathy

Dermatitis herpetiformis (DH) shares some clinical features and major histocompatibility complex (MHC) markers with gluten-sensitive enteropathy (GSE). We compared MHC haplotypes in 27 patients with DH, 35 patients with GSE, and normal controls. As in GSE, the frequencies of two extended haplotypes, [HLA-B8, SC01, DR3] and [HLA-B44, FC31, DR7], were increased in patients with DH. Distributions of fragments of extended haplotypes, consisting of some but not all of the elements of complete extended haplotypes, were analyzed to attempt to localize a susceptibility gene. Besides complete extended susceptibility haplotypes, (DR3, DQ2) and (DR7, DQ2) fragments were most common in GSE. In contrast, DH showed only a few such fragments but many instances of the fragment (SC01). The differences in distribution of these fragments in the two diseases were highly significant (P < 0.002). HLA-DQ2 and DR3 had the highest odds ratios for GSE, but the highest odds ratio for DH was for the complotype SC01. These findings suggest that the MHC susceptibility gene for DH is between class II and complotype regions, closest to the complotype, whereas that for GSE is in the class II region.

Detection and partial characterization of ocular cicatricial pemphigoid antigens on COLO and SCaBER tumor cell lines

Ocular cicatricial pemphigoid (OCP) is a chronic autoimmune inflammatory disease which affects the conjunctiva and other squamous epithelial mucous membranes resulting in a scarring process. It is characterized by the deposition of an anti-basement membrane zone (BMZ) antibody in vivo. Sera from 11 patients with active OCP were studied. Using monkey esophagus and normal skin as substrate, weak staining of the BMZ was observed in conventional indirect immunofluorescence (IIF) assay. Using salt split human skin as substrate, the OCP sera demonstrated binding to the epidermal side of the split, in low titers with weak staining. Ten of the 11 sera were positive on an immunoblot assay using COLO and SCaBER tumor cell lysates demonstrating 230, 205, 160, and 85 kD proteins. Sera from six bullous pemphigoid (BP) patients, with only cutaneous involvement and high titer of anti-BMZ antibody, as detected by IIF, also bound to 230, 160, and 85 kD proteins on both lysates in comigration experiments. Serum from five normal individuals and two patients each with severe atopic conjunctival disease, erythema multiforme with chronic conjunctivitis and systemic lupus erythematosus (SLE), did not demonstrate those bands. When the two lysates were first absorbed with BP sera and then the same lysates were immunoblotted with OCP sera, in all ten OCP sera the 230, 160, and 85 kD bands were eliminated and only a single 205 kD band was uniformly present. These results indicate that OCP sera recognize peptide(s) present in 230, 205 and 160 kD proteins in lysates from COLO and SCaBER tumor cells. These proteins contain the immunodominant region of the BMZ molecule(s) in which the OCP antigen(s) reside. The OCP antigen(s) appears to be distinct from the BP antigen(s).

MHC regulation of immune responses

The major histocompatibility complex is a group of complex genes situated on the short arm of chromosome 6 in humans. They play an important role in the regulation of the immune response. Autoimmune blistering disease provides an ideal model for studying the role of MHC in autoimmunity. The diseases are organ specific, and in some of them the relevant antigen has been cloned and sequenced. Such information on the antigen will help further define the interactions of the Ag, MHC, and TCR. Use of family studies hopefully will define and localize susceptibility alleles, so that any genetic susceptibility can be identified at the molecular level. It is from these molecular perspectives that molecular therapies could be assigned to restore the immune system.

Linkage of pemphigus vulgaris antibody to the major histocompatibility complex in healthy relatives of patients

Pemphigus vulgaris (PV) is an autoimmune disease caused by high concentrations of antibody to an epidermal cadherin. The disease is associated with two kinds of HLA-DR4, DQ8 haplotypes dominantly distributed among Jewish patients, and these plus DR6, DQ5 haplotypes in non-Jewish patients. Low levels of the PV antibody were found in 48% of a total of 120 asymptomatic parents, children, and siblings of 31 patients, thus exhibiting dominant inheritance. The inheritance of these low levels of antibody in asymptomatic relatives was linked to the major histocompatibility complex with a highly significant logarithm of the odds score of 9.07, almost always to a DR4 or DR6 haplotype of the patient. Disease appears to occur in susceptible individuals with low levels of antibody when a second factor, either environmental or genetic, induces high levels, sufficient to produce blisters.

Report on the sequence of DQB1*0301 gene in ocular cicatricial pemphigoid patients

Ocular cicatricial pemphigoid (OCP) is an autoimmune disease that affects the conjunctiva and other mucous membranes. Major histocompatibility complex (MHC) class II genes are important in autoimmunity because the antigen is presented to the T cell receptor in association with these molecules. A highly statistically significant association has been observed between patients with OCP and DQw7 (DQB1*0301) gene. DNA sequences of the second and third exons of the DQB1*0301 gene were determined in three OCP patients and compared with a control homozygous cell line for DQw7 from the Tenth International Histocompatibility Workshop. The sequences were identical in the patients studied and reference cell line. This data indicates that DQB1*0301 may only partly provide the enhanced susceptibility to get OCP and that another gene(s) in linkage disequilibrium with it and other factors may play an important role in the pathogenesis.

Isolation and partial purification of a melanocyte-stimulating hormone receptor from B16 murine melanoma cells. A novel approach using a cleavable biotinylated photoactivated ligand and streptavidin-coated magnetic beads

The alpha-melanocyte-stimulating hormone (alpha-MSH) receptor of B16 mouse melanoma cells was characterized by photoaffinity labelling using radiolabelled photoactive derivatives of alpha-MSH. A doublet band of 43-46 kDa representing a ligand-receptor complex was identified. A novel adaptation of the streptovadin/biotin-based affinity system was used to isolate the alpha-MSH receptor. A probe was synthesized which contained biotin connected to a photolabelled alpha-MSH analogue via a cleavable disulphide linker and which displayed high affinity for the alpha-MSH receptor. Streptavidin-coated magnetic beads were used as a solid support instead of an affinity column. Covalently linked probe-receptor complexes solubilized in Triton X-100 were equilibrated with the beads, and after magnetic separation and washing, specifically bound complexes were treated with dithiothreitol to cleave the disulphide bridge in the biotin-peptide spacer arm and so release the receptor-ligand complex. The identity of the isolated protein was established by SDS/PAGE analysis. Methods to achieve purification to homogeneity and to allow quantitative isolation of the receptor are discussed.

Association of DQw7 (DQB1*0301) with ocular cicatricial pemphigoid

Ocular cicatricial pemphigoid (OCP) is an autoimmune blistering disease that affects the conjunctiva and multiple mucous membranes. Class I and II and complement genetic markers of the major histocompatibility complex were studied in 20 Caucasian OCP patients and members of their families. Frequencies of individual alleles and common fixed or extended haplotypes in the patients were compared with those in normal family control haplotypes and with overall normal Caucasian haplotypes. The most striking increase compared with overall controls was noted in HLA-DQw3 (P = 0.006), unassociated with any extended haplotype. All but 1 of the 20 patients carried DQw3 in linkage with HLA-DR4 (increased significantly with P = 0.042 compared with overall normal genotype controls) or DR5. The DQw3, on analysis by restriction fragment length polymorphism in genomic DNA, was, in every instance, DQw7 (3.1, DQB1*0301). The frequency of DQB1*0301 in patient haplotypes compared with overall normal DR4 and DR5 DQw3-bearing haplotypes was statistically significantly increased (P less than 0.003, relative risk = 9.6). The distribution of homozygotes and heterozygotes for DQB1*0301 among the patients was consistent with dominant but not recessive inheritance of DQB1*0301 or a gene, probably a class II allele, in linkage disequilibrium with it as the major histocompatibility complex susceptibility gene for OCP.

Major histocompatibility complex haplotypes and class II genes in non-Jewish patients with pemphigus vulgaris

Previous studies demonstrated that HLA-DR4 was markedly increased among Ashkenazi Jewish patients with pemphigus vulgaris (PV), almost entirely as the common Jewish extended haplotype [HLA-B38, SC21, DR4, DQw8] or as the haplotype HLA-B35, SC31, DR4, DQw8, and that HLA-DR4, DQw8 was distributed among patients in a manner consistent with dominant expression of a class II (D-region or D-region-linked) susceptibility gene. In the present study of major histocompatibility complex (MHC) haplotypes in 25 non-Jewish PV patients, DR4, DQw8 was found in 12 of the patients and DRw6, DQw5 was found in 15. Only 3 patients had neither. Only 1 of the DR4, DQw8 haplotypes was [HLA-B38, SC21, DR4, DQw8] and 2 were HLA-B35, SC31, DR4, DQw8; most were the presumed fragments (SC31, DR4, DQw8) or (SC21, DR4, DQw8) or DR4, DQw8 with some other complotype. Of the patients with DRw6, DQw5, all were DRw14, DQw5, and 6 had a rare Caucasian haplotype, HLA-Bw55, SB45, DRw14, DQw5. Four of 6 of these were found in patients of Italian extraction, as was the 1 normal example. The non-Jewish patients were of more Southern European extraction than our controls. This suggests that there are two major MHC susceptibility alleles in American patients with PV. The more ancient apparently arose on a haplotype in the Jews, HLA-B38(35), SC21(SC31), DR4, DQw8, and spread to other populations largely as D-region segments. The other arose in or near Italy on the haplotype HLA-Bw55, SB45, DRw14, DQw5 and has also partially fragmented so that many patients carry only DRw14, DQw5. The available data do not permit the specific localization of either the DR4, DQw8- or the DRw14, DQw5-linked susceptibility genes.

Cicatricial pemphigoid

Cicatricial pemphigoid is a subepidermal blistering disease that involves the mucous membranes and the skin. The oral cavity and the eye are most frequently involved. The clinical course is of long duration, and often there is significant scarring that can have devastating sequelae. The majority of the patients are elderly. The disease is characterized by the in vivo deposition of an anti-basement membrane zone antibody. The anti-basement membrane zone antibody cannot be detected in the circulation by routine laboratory techniques. The pathogenesis is poorly understood, and the cause is not known. Cicatricial pemphigoid may remain localized to the oral cavity or the eye or the skin (Brunsting-Perry variety), or it may be generalized. It rarely occurs in children, and it may be drug induced. Efforts must be made to differentiate cicatricial pemphigoid from bullous pemphigoid, epidermolysis bullosa acquisita, linear IgA bullous disease, and other vesiculobullous disease. Early recognition and treatment can improve the prognosis and avoid surgical intervention. Topical therapy is beneficial and expedites healing. Intralesional corticosteroids are effective and can help reduce the dose of systemic steroids. Most patients require systemic corticosteroid therapy. Dapsone is also useful in treating cicatricial pemphigoid, especially in patients in whom systemic steroids are ineffective or in whom they have to be discontinued because of side effects. Immunosuppressive agents (azathioprine or cyclosphosphamide) are indicated in patients with progressive disease. Occasionally both drugs may be needed.

Major histocompatibility complex haplotype studies in Ashkenazi Jewish patients with pemphigus vulgaris

Of 26 Ashkenazi Jewish patients with pemphigus vulgaris, 24 (92.3%) carried the major histocompatibility complex (MHC) class II alleles HLA-DR4, DQw3, of which all were of the subtype DR4, DQw8. From studies of the patients and their families, haplotypes were defined. It was found that, of the patients who carried HLA-DR4, DQw8, 75% carried one or the other (and in one case, both) of two haplotypes [HLA-B38, SC21, DR4] or HLA-B35, SC31, DR4. The former is a known extended haplotype among normal Jews, with a frequency of 0.102, and the latter may also be an extended haplotype in this ethnic group, with a frequency of 0.017 among normal haplotypes from Jews. Of the remaining DR4-positive patients, all but one had a presumed D-region segment (defined as SC21, DR4, DQw8 or SC31, DR4, DQw8 with variable HLA-B) of these haplotypes. Only one patient had DR4, DQw8 without any other markers of the extended haplotypes. The number of homozygotes and heterozygotes for DR4, DQw8 was consistent with dominant but not recessive (P less than 0.01) inheritance of a class II or a class II-linked susceptibility gene for the disease. Since the disease is entirely attributable to the presence of an antibody to an intraepidermal intercellular cement substance, it is likely that the class II susceptibility gene (on [HLA-B38, SC21, DR4, DQw8], HLA-B35, SC31, DR4, DQw8, or their segments, in Jewish patients) controls the production of the antibody as a dominantly expressed immune response gene.

Autoimmunity and malignancy

In patients with autoimmune diseases malignancy is observed more frequently than in an age-matched control group. In strains of mice susceptible to autoimmune diseases, the incidence of lymphoreticular malignancies is increased. Although viruses have not been directly implicated in their pathogenesis or etiology, there are suggestions that slow viruses may be involved. Viruses have been found to be important in the development of lymphomas. Hence in genetically susceptible animals, viruses can initiate the autoimmune process. Prolonged stimulation of the autoimmune process or a prolonged state of immunodeficiency could trigger or activate genes or their products, which could result in the development of malignancy.

The relationship of pemphigus to neoplasia

A statistically increased incidence of malignancy has been observed in patients with pemphigus. A review of the literature reveals 42 cases of nonthymic malignancies and 18 cases of thymic malignancies. A significant predominance of men, with mean age at onset of 50 years, was observed. Pemphigus vulgaris is more common in patients with nonthymic neoplasms, whereas pemphigus foliaceus or pemphigus erythematosus and pemphigus vulgaris are equally common in patients with thymic neoplasms. Lymphoreticular malignancies, especially Kaposi's sarcoma, are most frequently observed. The majority of patients with nonthymic neoplasms have pemphigus before the detection of the malignancy and have a favorable 5-year survival rate after tumor resection. The majority of the patients with thymic neoplasms have a thymoma before the development of pemphigus. In some patients pemphigus develops after thymectomy and myasthenia gravis is often associated. Overall, 37 of the 60 patients, or 61%, had a neoplasm of the immune system.