Reduced hyaluronan in keloid tissue and cultured keloid fibroblasts

Extracellular matrix hyaluronan is prominent during wound healing, appearing at elevated levels early in the repair process. It is prevalent throughout the course of fetal wound healing, which is scar-free, but decreases late in adult wound repair, that is often marked by scarring. To determine whether aberrant hyaluronan metabolism is associated with the excessive scarring that characterizes keloids, cultured fibroblasts derived from keloids and from the dermis of normal human skin and scar were compared. Levels of hyaluronan in 48 h conditioned media of keloid-derived cultures were significantly lower than in cultures of normal skin and scar fibroblasts. Profiles of hyaluronan polymer size were comparable in these two cell types, suggesting that excessive hyaluronan degradation was not involved. Hydrocortisone decreased hyaluronan levels approximately 70% in the conditioned media of both keloid and normal fibroblasts. Diminished hyaluronan accumulation in keloid-derived cells compared with normal fibroblasts was also observed in an in vitro wound healing model. Histolocalization of hyaluronan in keloids, normal skin, and scar samples confirmed the biochemical observations that the dermis of keloids, which comprises most of the scar tissue, contained markedly diminished levels of hyaluronan. Alterations in hyaluronan in the epidermis overlying keloids, however, were also observed. A modest increase in hyaluronan staining intensity was observed in the epidermis of keloids, as well as changes in the patterns of distribution within the epidermis, compared with that in normal skin and scar. Increased hyaluronan was present in the granular and spinous layers of the keloid epidermis Abnormalities are present apparently in both the overlying epidermis as well as in the dermis of keloids. Aberrations in signaling between keloid stroma and keloid epidermis may underlie abnormalities that contribute to the excessive fibrosis characteristic of these lesions.

IgA1 is the major IgA subclass in cutaneous blood vessels in Henoch-Schönlein purpura

Henoch-Schönlein purpura (HSP) is characterized by palpable purpura predominantly involving the lower extremities. On direct immunofluorescence IgA can be seen deposited in the blood vessel walls of the superficial dermis. The subclass distribution of antibodies to this IgA was studied in the biopsies of 28 patients with HSP by direct immunofluorescence using anti-IgA1 and anti-IgA2 specific monoclonal antibodies. All 28 patients' biopsies demonstrated deposition of IgA1 while only one patient had IgA2 deposition. Positive and negative controls stained appropriately. This demonstrates that IgA1 is the dominant IgA subclass found in the skin in Henoch-Schönlein purpura.

IgA antibodies recognizing LABD97 are predominantly IgA1 subclass

Linear IgA bullous dermatosis is a rare acquired subepidermal blistering disease of the skin. A recognized antigen in linear IgA bullous dermatosis is a 97-kDa basement membrane zone protein termed LABD97. Previous studies, using immunofluorescent techniques, have suggested that the IgA response is restricted to the IgA1 subclass. We studied the IgA antibody subclasses in the sera of 6 patients that contained circulating IgA antibodies reactive with LABD97. The methods used included direct and indirect immunofluorescence and Western immunoblot. All patients tested had IgA1 anti-LABD97 antibodies detected by all 3 methods. Two patients had IgA2 antibodies detected by direct immunofluorescence. Three patients had IgA2 antibodies on indirect immunofluorescence. Two of these also had anti-LABD97 IgA2 antibodies and 1 had secretory component containing anti-LABD IgA antibodies on Western immunoblot. We conclude that the predominant IgA antibody subclass reactive with LABD97 in LABD is IgA1, although the IgA2 subclass may be involved in some cases.

Characterization of the antibody response in oesophageal cicatricial pemphigoid

Cicatricial pemphigoid (CP) is a subepidermal, autoimmune bullous dermatosis. It is classified as a clinical subset of bullous pemphigoid (BP). However, it differs from BP in some significant ways: (i) in CP mucosal involvement with clinical scarring is prominent; (ii) there is a prominent IgA class antibody response alone or in addition to the IgG class antibody response; and (iii) there is a heterogeneous antibody response in CP, whereas in BP the majority of the antibodies are directed against a 180-kDa hemidesmosomal protein, bullous pemphigoid antigen 2 (BPAg2). Oesophageal involvement in CP is a rare, but often devastating manifestation. In this study we examined the humoral autoimmune response in oesophageal CP, in an attempt to characterize the autoantibody reactivity profile. We used direct and indirect immunofluorescence and Western immunoblotting using normal human skin and oesophagus substrates. We studied patient sera over time in order to search for evidence of epitope spreading in these patients. All patients had positive direct immunofluorescence of perilesional oesophageal epithelium. All patients had positive circulating antibasement membrane zone autoantibody titres. There was a significant IgA class in addition to an IgG class autoantibody response. IgA and IgG antibodies demonstrated significant reactivity with BPAg2 and the 97 kDa linear IgA disease antigen on Western immunoblot suggesting intraprotein epitope spreading. There was no evidence of interprotein epitope spreading over time. Our findings suggest that there is a heterogeneous antibody response in oesophageal CP with the predominant antigen being BPAg2.

Bullous pemphigoid sera that contain antibodies to BPAg2 also contain antibodies to LABD97 that recognize epitopes distal to the NC16A domain

IgG antibodies from the sera of some patients with bullous pemphigoid (BP) react with a 180 kDa protein termed BPAg2. Antibodies in BP are directed to an extracellular noncollagenous domain of this protein termed NC16A. Our group has recently shown that a portion of the extracellular domain of BPAg2 is identical to LABD97 on the basis of amino acid sequencing. We evaluated sera from 33 patients with BP with circulating IgG antibodies on indirect immunofluorescence, which stained the epidermal side of split skin with titers ranging from 1:40 to 1:640. Immunoblotting was performed against (i) two preparations of proteins from epidermal extract, one containing BPAg2 and one containing LABD97, and (ii) the recombinant NC16A domain of the BPAg2 protein. Twelve sera reacted with the BPAg2 protein. Ten of these also reacted strongly with the NC16A domain. Nine of the 12 sera also reacted with the LABD97 antigen. Bound antibodies were eluted from the 97 kDa band and reapplied to split skin where they bound to the epidermal side. The eluted antibodies also reacted to the BPAg2 protein from the epidermal extract, but did not react with the NC16A domain on immunoblot. We conclude that these nine sera react with an epitope present within BPAg2 and LABD97 but not within the NC16A domain. This epitope is therefore distal to the previously described epitopes in BP. In BP, epitope spreading may occur and antibodies may be produced that recognize the distal portion of the BPAg2 molecule identical to LABD97 but that do not involve the NC16A domain.

The immunoglobulin A antibody response in clinical subsets of mucous membrane pemphigoid

BACKGROUND

Mucous membrane pemphigoid (MMP) is an immunobullous disease. In MMP there is frequently a mixed antibody response with the presence of IgA and/or IgG antibodies directed toward basement membrane zone antigens. The IgG antibody response in MMP has been studied, but the antigens to which the IgA antibodies react have not been studied.

OBJECTIVE

To determine the IgA autoantibody reactivity profiles in patients with MMP.

METHODS

Patients who had both ocular and oral MMP were compared with patients who had ocular or oral MMP and with patients who had cutaneous linear IgA disease (LABD) by Western immunoblot studies.

RESULTS

Five of 15 MMP patients and 1 of 5 LABD patients had IgA antibodies reactive with the 180-kD bullous pemphigoid antigen. Seven of 15 MMP patients had IgA antibodies reactive with the 97-kD LABD antigen.

CONCLUSION

Major antigens in IgA MMP are the 180-kD bullous pemphigoid antigen and the 97-kD LABD antigen.

The 97 kDa linear IgA bullous disease antigen is identical to a portion of the extracellular domain of the 180 kDa bullous pemphigoid antigen, BPAg2

IgA autoantibodies from the sera of some patients with linear IgA bullous dermatosis (LABD) recognize a 97 kDa antigen (LABD97) located in the lamina lucida of the basement membrane zone. As LABD autoantibodies do not react with the 180 and 230 kDa proteins recognized by bullous pemphigoid autoantibodies, LABD97 has been thought to represent a separate lamina lucida protein. In this study, we purified LABD97 from the extract of human epidermis using a monoclonal antibody immunoaffinity column and analyzed the amino acid sequence of the N terminus of purified LABD97. This revealed a 16 amino acid sequence that was identical to a previously reported sequence of the 180 kDa antigen in bullous pemphigoid (BPAg2). The N terminus was located 41 amino acids downstream from the carboxyl end of the transmembrane domain of BPAg2 and 11 amino acids downstream from the MCW-1 domain, the predominant bullous pemphigoid epitope. Purified LABD97 was subsequently enzymatically digested with endoproteinase Arg C and separated by chromatography, which resulted in multiple peptide fractions. Fourteen of these fractions were subjected to amino acid sequencing. The amino acid sequence of the peptide fractions, totaling 205 amino acids, were identical to sequences contained within the extracellular domain of BPAg2. Whereas the predominant epitope identified with bullous pemphigoid sera is located in the noncollagenous region of this protein, the epitope recognized by LABD sera is either within or adjacent to the collagenous portion. We conclude that LABD97 represents a portion of the extracellular domain of BPAg2 and that the IgA autoantibodies are directed against an epitope within or adjacent to a collagenous domain.

Expression of c-fos in cultured human nevus cells: an increase over melanocytes and melanoma cells

Nevus cells exhibit growth characteristics in culture which differentiate them from melanocytes and melanoma cells. We examined the expression of c-jun, c-fos and jun-B mRNA levels in cultures of different melanocytic cell types to determine if biologic differences among these cells was due to their level of proto-oncogene expression. Because cell growth and differentiation are also known to be affected by serum conditions, the expression of c-jun, c-fos and jun-B was examined under normal serum conditions and serum starved and repleted conditions which stimulates proto-oncogene expression. Expression of c-jun and jun-B was not significantly different among the cell types studied under normal serum conditions, or serum starved and refed conditions and c-fos was not detectable in any of the unstimulated cell types. In contrast, when the cells were serum starved and refed, the level of c-fos expression was uniformly increased (2-10 fold) in 3 different nevus cell lines. This increase was not seen in normal melanocyte cultures or 2 melanoma cell lines. With serum deprivation and repletion, c-fos was also elevated in 1 melanoma cell line. We conclude that the regulation of the proto-oncogene c-fos is different in nevus cells than in normal melanocytes, which may contribute to the different growth characteristics seen with nevus cells.

Deposition of granular IgA relative to clinical lesions in dermatitis herpetiformis

OBJECTIVE

To compare the deposition of IgA and C3 in the skin of patients with active dermatitis herpetiformis relative to the sites of disease.

DESIGN

In the phase 1 study, skin biopsy specimens were obtained from erythematous perilesional skin, nonerythematous perilesional skin, and never-involved skin. In the phase 2 study, specimens from the nonerythematous perilesional and uninvolved skin from the same anatomic region were sampled.

SETTING

The Dermatology Clinic at the University of Utah Health Sciences Center, Salt Lake City.

PATIENTS

Patients with known dermatitis herpetiformis: 19 patients in the phase 1 study and 15 patients in the phase 2 study. Suppressive medications were stopped for 48 to 72 hours after biopsy specimens were obtained. All patients had active disease at the time that biopsy specimens were taken.

MAIN OUTCOME MEASURE

The intensity of IgA and C3 immunofluorescent staining in 6 sections from each skin biopsy specimen was graded by using a semiquantitative scale (0 to 3+) in a blinded fashion by a single observer.

RESULTS

Deposition of IgA was more intense in noninflamed perilesional skin in 11 of 19 patients compared with that in erythematous skin (P < .05). Erythematous skin was negative for IgA in 16% (3/19) of the specimens. Noninflamed perilesional skin showed more intense IgA deposition in 18 of 19 specimens compared with that in never-involved skin (P < .01); C3 was more intense in erythematous skin (P < .01). In the phase 2 study, skin from the same anatomic region revealed greater deposition of IgA near lesions in 12 of 15 patients (P < .001).

CONCLUSIONS

In patients with dermatitis herpetiformis, IgA is not uniformly distributed throughout the skin, and IgA is present in greater amounts near active lesions. The preferred biopsy site for the diagnosis of dermatitis herpetiformis is normal-appearing skin that is adjacent to an active lesion.

IgA antibodies in chronic bullous disease of childhood react with 97 kDa basement membrane zone protein

Chronic bullous disease of childhood (CBDC) is an autoimmune blistering disease occurring in prepubertal children. Both CBDC and its adult counter-part, linear IgA bullous dermatosis (LABD), are characterized by linear deposition of IgA along the cutaneous basement membrane zone (BMZ). Circulating IgA antibody in LABD has been found to bind to a 97-kDa BMZ antigen, whereas the antigen in CBDC has not been well characterized. The purpose of this study was to evaluate the immunoreactivity of BMZ IgA antibodies in a series of CBDC patients. We evaluated 12 sera from patients with CBDC with circulating IgA anti-BMZ antibodies on indirect immunofluorescence (IIF), which stained the epidermal side of split skin with titers ranging from 1:20 to 1:640. Immunoblotting was performed against two preparations of BMZ proteins: one enriched with the two bullous pemphigoid antigens (BP230, BP180) and one enriched with the LABD antigen (LABD97). Eight of the twelve sera reacted with a 97-kDa protein that co-migrated with the protein detected in many LABD sera. The intensity of the reaction on immunoblot correlated with serum antibody titers. There was no consistent pattern of reactivity of the IgA anti-BMZ antibodies with either the BP230 or BP180 antigens, although two sera reacted with several higher molecular mass proteins (160-200 kDa). The significance of this reactivity was examined with immunoblotting using BMZ-affinity-purified antibodies, and ELF using nitrocellulose-eluted antibodies. One serum also contained anti-BMZ IgA antibodies that reacted with a 180-kDa protein, corresponding to BP180. We conclude that IgA antibodies in CBDC sera recognize a 97-kDa BMZ antigen present on the epidermal side of BMZ split skin that co-migrates with the antigen previously identified in LABD. These findings suggest that CBDC and LABD are the immunologically related disorders occurring in different age groups.

Interobserver concordance in discriminating clinical atypia of melanocytic nevi, and correlations with histologic atypia

BACKGROUND

The clinical features attributed to atypical (formerly ¿dysplastic") nevi and to the atypical multiple mole melanoma syndrome have been used in clinical practice, as well as experimentally, to assign melanoma risk. Little information is available, however, on the interobserver reliability in assessing those features.

OBJECTIVE

Our purposes were to quantify interobserver and intraobserver concordances in recognizing certain atypical characteristics of nevi and to correlate the clinical assessments with the histologic characteristics.

METHODS

Three observers evaluated clinical photographs of 100 pigmented lesions (predominantly melanocytic nevi, with some lentigines and seborrheic keratoses) from 95 subjects, of whom 85 were family members of four multiple melanoma kindreds and 10 were spouses. Each lesion was rated for border irregularity, color variegation, surface contour irregularity, pigment diffusion, and macularity versus papularity. Predictions were made as to the histologic diagnoses and presence of melanocytic atypia for those lesions judged to be nevi.

RESULTS

The pair-wise concordances before agreement on specific criteria were quantified by kappa statistics, which indicated slight to fair agreement in judging the atypical clinical characteristics; concordances increased to moderate levels after consensus development of criteria for color variegation and assessment of macularity, but agreement on the other features remained limited. Whereas macularity and color variegation did correlate somewhat with higher grades of histologic atypia, correlations were generally low between the clinical and histologic diagnoses.

CONCLUSION

There is limited interobserver reliability in the clinical assessment of nevus atypia, although correlations do exist between some atypical characteristics and grades of histologic atypia. Because of the low concordances, the clinical discrimination of the melanoma-associated atypical nevus phenotype should rely more on quantitative aspects of the trait, such as total numbers or maximal sizes of nevi, rather than on the subjective determinations of atypia.

Survival and histopathologic characteristics of human melanocytic nevi transplanted to athymic (nude) mice

Melanocytic nevi (n = 406) covering a range of sizes and gross morphologic features were excised from human donors, sampled for histologic diagnosis, and transplanted to athymic (nude) mice. Ninety percent of these xenografts survived transplantation, of which a subset was irradiated daily with ultraviolet light to promote neoplastic transformation. Over 16 weeks of observation, nearly all grafts histologically showed focal inflammatory cell infiltration and fibrosis, progressing in approximately 30% of grafts to complete regression at final observation. During the inflammatory phase, the nevi often had junctional intraepidermal melanocytic hyperplasia in a lentiginous pattern, with cytologic hypertrophy, dendritic morphology, and hypermelaninization. These changes were evident in approximately 20-30% of nevi where they were absent before transplantation, suggesting that host factors, such as those related to the immune response, had stimulated growth. Graft survival was independent of nevus size and initial histologic diagnosis. No melanomas developed in any of the grafts, either spontaneously or with ultraviolet irradiation. These results indicate that successful transplantation can be achieved in a high proportion of human nevus xenografts and that the majority survive for a period of time that would be sufficient for experimental studies. The host response, however, has effects on intraepidermal melanocytic growth that lead to progressive fibrous replacement of the nevus, introducing significant artifacts that compromise the model. Furthermore, malignant transformation of engrafted melanocytes seems to be a rare event, which would limit studies of neoplastic progression in the transplanted melanocytes. Nonetheless, the intraepidermal melanocytic pattern described here evidently constitutes one pattern of melanocyte growth that could be exploited experimentally for studies of growth and differentiation control in melanocytes.

Penetrance and expressivity of the chromosome 9p melanoma susceptibility locus (MLM)

A susceptibility locus for familial melanoma has been localized to the short arm of chromosome 9. Penetrance of melanoma was estimated by calculating the Kaplan-Meier function and fitting a log normal hazard function in 124 gene carriers in three 9p-linked kindreds. The penetrance of the gene for melanoma was estimated to be 53% by age 80. Additionally, nevus counts, skin type, and sun exposure histories were gathered for 119 individuals in two kindreds. Gene carriers were found to have higher nevus counts and nevus densities than non-gene carriers. Among gene carriers, individuals with melanoma were found to have more sun exposure within each skin type than gene carriers without melanoma. These analyses suggest that the 9p melanoma susceptibility is related to total number of nevi and that it interacts with other genetic and environmental factors to produce melanoma.

Genetics of cutaneous melanoma

A portion of melanoma is familial and has been associated with atypical mole syndrome. This review outlines the current understanding of the genetics of melanoma and the relationship to cutaneous nevus phenotypes. A review of genetic studies of melanoma is presented, including linkage studies. Data from a linkage study of 12 Utah kindreds and one Texas kindred are detailed. There is strong evidence both for a genetic component to melanoma and, to a lesser extent, for a genetic component to the atypical mole phenotype. Reports of linkage of melanoma/dysplastic nevus syndrome to chromosome 1p markers are now strongly in doubt. The Utah group has shown strong evidence of linkage of melanoma to chromosome 9p21 without evidence for heterogeneity. This is in the same region where chromosomal deletions are common in tumors of numerous tissues. We conclude that there is a specific melanoma susceptibility locus located on chromosome 9p. The combination of the results of linkage in families with multiple cases of melanoma and the deletion of this chromosomal region in sporadic cases of melanoma strongly suggests that this melanoma susceptibility locus acts as a tumor suppressor.

A multiobserver, population-based analysis of histologic dysplasia in melanocytic nevi

BACKGROUND

Nevi that are clinically atypical and histologically dysplastic have been associated with increased melanoma risk. There are few reproducibility studies or population-based studies of nevus histology.

OBJECTIVE

Our purpose was to quantify concordance in histologic diagnosis of melanocytic lesions among a diverse group of pathologists, to assess intraobserver concordance by comparing readings of the same slide as well as of adjacent recuts from the same block, to correlate histology with nevus appearance and melanoma risk, and to estimate the range of prevalence of histologic dysplasia.

METHODS

Histologic slides were prepared from 149 tissue blocks of pigmented lesions from melanoma cases, relatives, and controls. Six dermatopathologists independently evaluated the lesions for histologic dysplasia, without prior agreement on criteria.

RESULTS

According to kappa statistics, intraobserver reproducibility was substantial, and interobserver concordance was fair, despite differences in criteria. The estimated prevalences of histologic dysplasia for the six pathologists ranged from 7% to 32%. Histologic dysplasia was correlated with nevus size for most observers, confounding the observed correlation between nevus appearance and histology.

CONCLUSION

Although experienced dermatopathologists use different diagnostic criteria for histologic dysplasia, their usage is consistent. Histologic changes ascribed to melanocytic dysplasia are prevalent in the white population for all pathologists. The term nevus with histologic dysplasia should be used in preference to dysplastic nevus.

Age-dependent changes of hyaluronan in human skin

Hyaluronan is a major component of the extracellular matrix of skin. The large volume of water of hydration associated with hyaluronan may be a mechanism for maintaining the normal hydration of skin. As such, decreasing levels of hyaluronan deposition might underlie the changes associated with the aging process. To test this hypothesis, hyaluronan levels were determined in extracts of skin obtained at autopsy from individuals of different ages. However, no significant differences in hyaluronan concentrations were found. The distribution of hyaluronan polymer sizes in various extracts did not change as a function of age as measured by size exclusion chromatography. However, major differences in hyaluronan extractability did occur as a function of age. Sequential extraction was performed utilizing 1) 0.1% Triton X-100, 2) 4 M guanidine-HCl, and 3) papain digestion, to release species of hyaluronan progressively more tightly associated with tissue. With advancing age, hyaluronan polymers became progressively more tissue associated. The proportion of hyaluronan released after papain digestion increased from 7% of the total in fetal to 23% of the total in senescent skin. Finally, histolocalization of hyaluronan was examined in full-thickness sections of human skin of different ages. Major differences in compartmentalization were found. We conclude that neither the concentration nor polymer size of hyaluronan changes as a function of age. However, enhanced association with tissue occurs, presumably through hyaluronan-binding proteins and alterations in the histolocalization of hyaluronan. Such observations may underlie some of the changes in human skin that occur with aging.

Antigenic specificity of antibodies from patients with linear basement membrane deposition of IgA

We reviewed the immunoreactivity of sera binding to the epidermal side of basement membrane split skin from 13 adults and 8 children with IgA alone, 9 adults with IgA and IgG and 7 adults with IgA and ocular pemphigoid. Immunoblots were done against previously described 45-, 97-, 180- and 230-kD antigens, and reactivity was confirmed by elution of antibody from nitrocellulose and binding to the basement membrane. Ten of 13 adults and 7 of 8 children reacted with the 97-kD antigen. Sera with both IgA and IgG reacted in varying patterns and on occasion with more than 1 antigen. All 7 patients with ocular cicatricial pemphigoid reacted uniquely with a 45-kD antigen.

Antigen identification in drug-induced bullous pemphigoid

Immunobullous diseases usually develop spontaneously, but drug-induced bullous disease develops in a small subgroup of patients. We examined a patient in whom bullous pemphigoid developed after she received enalapril for treatment of hypertension. IgG antibody directed against a 230 kd antigen was identified. The eluted IgG autoantibody was shown to bind to the basement membrane zone on split skin. This study demonstrates that drug-induced bullous pemphigoid autoantibody in this patient was directed against the same antigen as the spontaneous bullous pemphigoid antigen.

Identification of a basement membrane zone antigen reactive with circulating IgA antibody in ocular cicatricial pemphigoid

Ocular cicatricial pemphigoid is a rare vesiculobullous disease characterized by linear deposition of IgG and/or IgA along the basement membrane zone of conjunctival biopsies. This study identifies a tissue antigen detected by ocular cicatricial pemphigoid patient sera. Patient selection was based on the presence of only ocular involvement and a positive direct immunofluorescence of conjunctiva. We evaluated patient and control sera using indirect immunofluorescence of basement membrane zone separated skin, Western blot, and purified antibodies from nitrocellulose and epidermal sheets. Direct immunofluorescence performed on the patients' conjunctival biopsy showed linear deposition of IgA along the basement membrane zone in all seven patients, and five of seven also demonstrated deposition of IgG along the basement membrane zone. Indirect immunofluorescence performed on the patients' sera demonstrated linear deposition of IgA along the epidermal side of the basement membrane zone of ethylenediaminetetraacetic acid-separated skin in all seven patients. IgA titers ranged from 1:20 to 1:80. No IgG was detected. Immunoblots detected IgA binding to a 45-kD antigen in all patients as well as sporadic IgA binding to a number of other proteins. Immunoblots stained with sera from patients did not show reactivity to the 230- or 180-kD bullous pemphigoid antigens or the 97-kD linear IgA bullous dermatosis antigen. Eluting IgA from the 45-kD region and other regions revealed that only antibodies eluted from the 45-kilodalton region bound linearly to the basement membrane on separated skin. Purification of IgA using epidermal sheets confirmed that the antibody responsible for staining on indirect immunofluorescence bound to the 45-kD region on Western blot. Sera from normals and patients with bullous pemphigoid, dermatitis herpetiformis, and linear IgA bullous dermatosis failed to demonstrate basement membrane zone IgA on elution of the 45-kD region. We conclude that these ocular cicatricial pemphigoid sera contain a unique IgA antibody that binds to a 45-kD basement membrane zone antigen.