The autoantibody response to Ro/SSA in cutaneous lupus erythematosus

BACKGROUND AND DESIGN

Seventeen patients with subacute cutaneous lupus erythematosus (SCLE) were compared with 15 patients with discoid lupus erythematosus (DLE) to evaluate the relationship of 60- and 52-kd Ro/SSA autoantibodies to the clinical diagnosis and to evaluate assays for anti-Ro/SSA.

RESULTS

All serum samples from patients with SCLE had precipitating anti-Ro/SSA antibodies in immunodiffusion, and all had high titer anti-60-kd Ro/SSA in enzyme-linked immunosorbent assay. Immunoblotting was inadequately sensitive for detecting anti-60-kd Ro/SSA. Fifteen patients with SCLE had anti-52-kd Ro/SSA (11 high titer, four low titer). Only one of the 15 patients with DLE had precipitating, high-titer anti-Ro/SSA. Nine other patients with DLE had low-titer anti-60-kd Ro/SSA, and four had low-titer anti-52-kd Ro-SSA. Low-titer anti-Ro/SSA did not confer an increased risk for photosensitivity in the DLE group.

CONCLUSIONS

High-titer, precipitating antibodies to Ro/SSA are typical of SCLE and unusual in DLE. Low-titer, nonprecipitating antibodies to Ro/SSA are common in DLE and could be an indication of pathogenic factors shared with SCLE. However, low titers of anti-Ro/SSA do not confer a significant risk for SCLE skin lesions. For the purpose of clinical evaluation of skin disease, immunodiffusion assays for anti-Ro/SSA are cost-effective and informative.

Increase in antimicrobial-resistant Salmonella infections in the United States, 1989-1990

To assess factors associated with antimicrobial-resistant Salmonella infections and trends in resistance, a prospective study of patients with culture-confirmed salmonellosis was done in 1989-1990. Patients with resistant infections were more likely than those with susceptible infections to be hospitalized (P = .006), to be < 1 year old (P = .003), to be black (P = .013), and to have recently been treated with an antimicrobial agent (P = .085). Compared with data from a similar study in 1979-1980, increases were seen in the percentage of patients with resistant infections (from 17% to 31%), in the resistance to ampicillin (10% to 14%), and in the frequency of isolates found in blood (1% to 11%). These data show that treatment of Salmonella infections may be complicated by growing resistance to clinically important antimicrobial agents and by an increasing frequency of extraintestinal complications. Antimicrobial agents with little demonstrated resistance should be considered for patients with complicated illness and at high risk of having a resistant infection.

Autoantibodies of neonatal lupus erythematosus

The most common manifestations of neonatal lupus erythematosus (NLE) are cutaneous lupus and congenital heart block. Autoantibodies to Ro/SSA occur in almost all cases of NLE. The autoantibody response to Ro/SSA is complex, and antibodies may be detected to 60-kD Ro/SSA, 52-kD Ro/SSA, La/SSB, and U1 ribonuclear protein in anti-Ro/SSA-positive sera. Which of these anti-Ro/SSA-related autoantibody specificities are important in the clinical expression of NLE is not conclusively established. We examined the autoantibody specificities in 20 maternal NLE sera to determine whether autoantibody specificities correlate with the clinical findings and to evaluate the relative importance of autoantibodies to the different Ro/SSA-associated proteins. Autoantibodies were examined using immunodiffusion, immunoblotting, and enzyme-linked immunosorbent assay. Eleven babies had NLE skin disease, 11 had heart block, and two had both skin disease and heart block. All 20 maternal sera had antibodies to 60-kD Ro/SSA. Eighteen of the 20 had antibodies to 52-kD Ro/SSA, nine had antibodies to La/SSB, and one had antibodies to U1 ribonuclear protein. The prevalence of anti-La/SSB was the same in the skin-disease and heart-block subsets of NLE. Titers of anti-60-kD Ro/SSA were significantly (p < 0.02) lower in NLE skin disease maternal sera than in the NLE heart-block maternal sera. These results point out the importance of 60-kD Ro/SSA as a potential target in NLE. We speculate that the lower titers of anti-60-kD Ro/SSA in the sera from mothers of babies with skin disease may be due to substantial deposition of antibodies in the mothers' and babies' skin, leading to lower circulating titers, or may reflect a lower threshold for development of skin disease than for heart block.

The importance of nonimmune factors in reconstitution by discordant xenogeneic hematopoietic cells

Bone marrow transplantation has been shown to induce donor-specific tolerance in rodent models. This approach could potentially be applied to xenotransplantation across discordant species barriers. To evaluate host factors resisting hematopoietic cell engraftment, we have developed two model systems utilizing the combination of swine into severe combined immunodeficient (SCID) mice. SCID mice lack functional B and T lymphocytes, and can therefore be used to evaluate nonimmune factors resisting marrow engraftment, and for adoptive transfer studies to test the role of immune cells and antibodies. First we transplanted swine bone marrow cells into SCID mice conditioned with whole-body irradiation (4 Gy). For nine weeks following the intravenous administration of 10(8) swine bone marrow cells, up to 3.8% of peripheral blood leukocytes were of swine origin, as determined by flow cytometry (FCM). These cells were all of the myeloid lineage. Swine IgG was also detectable in the serum for up to 14 weeks. The bone marrow of the reconstituted mice contained low percentages of swine myeloid cells, and swine myeloid progenitors could be detected for up to 20 weeks after bone marrow transplantation. In a second model, we grafted thymus and liver tissue from 45-69-day-old swine fetuses under the kidney capsule of 4 Gy-irradiated SCID mice. A suspension containing 10(8) swine fetal liver cells (FLC) was also administered i.p. Long-term repopulation with swine T cells was observed, with up to 1.5% swine T cells detected in the WBC, peritoneum, and spleen for at least 5.5 months postgrafting. These T cells expressed either CD4 or CD8, whereas up to 17.6% of cells in the thymic grafts expressed both CD4 and CD8. The i.p. FLC suspension was required for optimal long-term graft maintenance. Our studies show that (1) low level myeloid and B lymphocyte reconstitution can be achieved by transferring adult swine BMC to irradiated SCID recipients; (2) swine myeloid progenitors were detectable long-term in BMC of these mice, suggesting that stem cell engraftment was achieved; and (3) T cell reconstitution of SCID mice by swine progenitors requires cotransplantation of a swine stromal environment, as is provided by fetal swine thymus/liver grafts. We conclude that nonimmune factors such as those provided by species-specific stromal environments are important for reconstitution of some lineages by discordant hematopoietic stem cells.

Outbreaks of Salmonella enteritidis infections in the United States, 1985-1991

The spread of Salmonella enteritidis infections in the United States was tracked to identify potential risk factors and preventive measures. Isolation rates and information regarding outbreaks of S. enteritidis from 1985 through 1991 were determined by reports to the national Salmonella surveillance system and through the foodborne disease outbreak surveillance system. From 1985 through 1991, 380 outbreaks were reported involving 13,056 ill persons and 50 deaths. The proportion of Northeast outbreaks fell from 81% in 1985 to 55% in 1991 as the number of outbreaks in other areas increased. Grade A shell eggs were implicated in 82% of outbreaks. Case-fatality rates in nursing homes and hospitals were 70 times higher than in other settings. Cultures of environmental or animal specimens from all farms tested yielded S. enteritidis. Eggborne S. enteritidis infections are a major public health problem. Preventive measures, including educating consumers about proper handling of eggs, using pasteurized eggs, and controlling infections on egg farms, may stem the impact of this disease.

Neonatal lupus liver disease

Neonatal lupus erythematosus (NLE) is an autoimmune disease characterized by complete congenital heart block and/or transient skin lesions of subacute cutaneous lupus erythematosus. We report that in approximately 10% of cases of NLE with heart block or skin disease, liver disease also occurs (4 of 35 cases in our series). Cholestasis was the major feature in our cases. Although the cholestasis may be severe, the disease process appears to be transient and surviving babies have been healthy on follow-up. In one liver examined for antibody deposition, IgG antibody deposits, presumably of maternal origin, were present. Three maternal sera were examined for autoantibodies, including liver-specific autoantibodies. No liver-specific autoantibodies were found. Rather, the maternal autoantibodies too were the ubiquitous Ro/SSA-associated autoantigens. The autoantibodies bound the 60 kDa SSA/Ro ribonuclear protein (three of three sera), the 52 kDa SSA/Ro protein (two of three sera) and the SSB/La ribonuclear protein (two of three sera).

Antimicrobial-resistant Salmonella spp isolated from healthy broiler chickens after slaughter

Of 105 Salmonella organisms of any serotype selected from a sample of 1,824 serotyped salmonellae isolated during a nationwide bacteriologic survey of healthy broiler chickens after slaughter, 60 (57%) were resistant to 1 or more antimicrobial agents and 47 (45%) were resistant to 2 or more agents. Highest resistance was to tetracycline (45%), streptomycin (41%), sulfisoxazole (19%), gentamicin (10%), and trimethoprim/sulfamethoxazole (8%). Additional isolates of S typhimurium, heidelberg, agona, and enteritidis were selected from the sample of 1,824 isolates for testing because of the high frequency with which these 4 serotypes are isolated from human patients. The highest frequency of resistance among 104 isolates of S heidelberg, 92 isolates of S typhimurium, and 30 isolates of S agona was to streptomycin (33 to 57%), sulfisoxazole (33 to 50%), tetracycline (26 to 50%), and gentamicin (13 to 40%); 51 to 63% of these isolates were resistant to 1 or more agents and 37 to 59% were resistant to 2 or more agents. Resistance to ampicillin among these 3 serotypes was uncommon (0 to 4%). In contrast, 15 of 19 tested isolates (79%) of S enteritidis were resistant to ampicillin and 13 of the 19 isolates (68%) were resistant only to ampicillin. This pattern of resistance was associated with a specific bacteriophage type and indicated the potential role of bacterial clones in determining the frequency and patterns of antimicrobial resistance in populations of broiler chickens. Resistance to gentamicin and trimethoprim/sulfamethoxazole was higher than that previously reported and is of public health concern because of the frequency with which these drugs are used to treat bacterial infections in human patients.

Neonatal lupus erythematosus

Neonatal lupus erythematosus (NLE) is an autoimmune disease whose major findings are subacute cutaneous lupus erythematosus (SCLE) skin lesions and congenital heart block. Babies have maternal anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies. Anti-Ro/SSA are the predominant autoantibodies, having been found in about 95% of cases. The autoantibodies pass through the placenta from mother to child. Skin disease resolves at about the time that maternal autoantibodies can no longer be detected in the baby. NLE therefore provides the strongest clinical evidence that autoantibodies are involved in at least some manifestations of lupus erythematosus, but there is as yet no definitive evidence implicating autoantibodies in the disease process. Skin disease usually begins after birth, is transient, and does not result in scarring. Cardiac disease begins in utero, and the heart block is almost always permanent. Many babies require pacemakers, and about 10% die from complications related to cardiac disease. In some cases, transient liver disease or thrombocytopenia have been observed. Individuals who had NLE usually have healthy childhoods but may develop autoimmune disease in adulthood. Whether the later development of autoimmune disease is a common or an unusual event is not yet known. Mothers of babies with NLE may be asymptomatic initially, but with time usually develop symptoms of autoimmune disease. The most typical constellation of symptoms in our group of approximately 30 mothers of babies with NLE is that of Sjögren's syndrome. Most babies exposed to anti-Ro/SSA autoantibodies during gestation will not develop NLE. There is no test to determine prospectively which babies will be affected. Treatment during gestation is still controversial and, if attempted, should be reserved for fetuses with potentially life-threatening disease. Treatment after birth consists of topical management for skin disease and pacemaker implantation, if necessary, for heart block. Systemic steroids may be given for serious internal disease.

Clinical, histologic, and immunofluorescent distinctions between subacute cutaneous lupus erythematosus and discoid lupus erythematosus

Subacute cutaneous lupus erythematosus (SCLE) was originally described and distinguished from discoid lupus erythematosus (DLE) on the basis of clinical examination of the skin, but subsequent reports have questioned the concept of SCLE as a marker of a unique subset of LE patients. We classified 27 lupus patients, on the basis of cutaneous exam, as having discoid lupus skin lesions, subacute cutaneous skin lesions, or systemic lupus erythematosus (SLE) without DLE or SCLE lesions. Clinical features most characteristic of SCLE rather than DLE were superficial, non-indurated, non-scarring lesions, and photosensitivity, with lack of induration being the single most helpful finding. Histologic examination of lesional skin showed a relatively sparse, superficial infiltrate in SCLE and a denser, deeper infiltrate in DLE. A distinctive pattern of staining with direct immunofluorescence, particulate epidermal IgG deposition, was found in seven of seven SCLE patients (all anti-Ro/SSA positive) and none of the other patients. This distinctive pattern can be reproduced experimentally when anti-Ro/SSA autoantibodies are infused into human skin-grafted mice. Particulate dermal-epidermal junctional staining was the pattern seen in the patients who did not have SCLE. Clinically defining SCLE as a superficial inflammatory form of cutaneous lupus (i.e., considering lesions to be DLE if they are indurated) results in a meaningful segregation of SCLE and DLE patient groups. The epidermal IgG deposits unique to SCLE provide independent evidence that the clinical findings that were used to identify the patient groups actually identify distinctive cutaneous lupus subsets. The observation that antibodies are present in a different location in the skin in SCLE than in DLE indicates that SCLE and DLE are likely to have different pathomechanisms.

Neonatal lupus erythematosus syndrome: analysis of C4 allotypes and C4 genes in 18 families

We examined 18 families with infants who had neonatal lupus erythematosus (NLE) syndrome to determine whether abnormalities in C4 phenotypes and genotypes were an additional risk factor for this syndrome. Fifteen of 18 mothers of infants with NLE (83%) had C4 null allotypes compared with 36% of population controls (p = less than .001). This increased frequency was due mainly to the presence of C4A null allotypes (11/18, 61%). C4 gene abnormalities, i.e., deletion or probable duplication, were present in 100% (16/16) of mothers of infants with NLE. The most common molecular genetic abnormality in mothers of infants with NLE in this study was deletion of C4A genes. Duplication of C4A and C4B loci was also commonly seen. Duplication of C4A genes was detected only in mothers of infants with complete congenital heart block (CCHB), and duplication of C4B was detected only in mothers of infants with dermatitis. No significant increase in C4A or C4B null allotypes or protein deficiencies was noted in mothers of infants with neonatal lupus when compared with anti-Ro(SS-A)-positive mothers delivered of clinically normal infants. Fathers of infants with NLE showed a trend toward increase in C4B null allotypes when compared with population controls (75%, 3/4, p = .06). The two infants with CCHB examined were C4B protein-deficient, in contrast to infants with lupus dermatitis, who had frequent C4B null allotypes but no C4B protein deficiency. C4B null allotypes were not seen in unaffected siblings of infants with NLE and in only 1 of 7 anti-Ro(SS-A)-positive mothers who delivered clinically normal infants. We conclude that inheritance of C4A null allotypes is not predictive of increased risk of neonatal lupus when present in anti-Ro(SS-A)-positive women. Examination of paternal and maternal C4 genes of additional infants with NLE, in particular those with CCHB, and of normal infants born to anti-Ro(SS-A)-positive mothers--and of the normal infants' parents--is required to determine if abnormal C4B genes are a critical factor rendering susceptibility to the NLE syndrome.

Left ventricular mechanics in the preterm infant and their effect on the measurement of cardiac performance

The effects of the transition from fetal to postnatal circulation on left ventricular geometry, wall motion, and echocardiographic measurements of function in the human preterm infant are largely unknown. To determine whether abnormalities in left ventricular geometry are present in the normal preterm infant after birth and, if so, for how long, and to examine possible contributing factors and their effect on the measurement of cardiac performance, we obtained serial echocardiograms of 14 healthy preterm infants (gestational age, 33 +/- 2 weeks; birth weight, 1940 +/- 470 gm) at 9.5 +/- 3.5 days of age (time 1) and again at 51 +/- 16 days (time 2). Left ventricular shape and wall motion were measured and estimates of wall stress and mass were made. Performance was assessed by standard M-mode shortening fraction and by transverse two-dimensional area shortening. At time 1 septal flattening caused distortion of left ventricular shape. As the patients grew older, septal flattening resolved and the left ventricle tended to assume a circular cross-sectional shape. Wall-motion analysis demonstrated poor motion of the midseptum and anterior free wall at time 1, which improved at time 2 (p = 0.06). Left ventricular mass increased from 24 +/- 5 to 41 +/- 7 gm/m2 (p = 0.0001) and wall stress decreased from 49 +/- 21 to 38 +/- 13 gm/cm2 (p = 0.005) between time 1 and time 2. Shortening fraction was lower at time 1 than at time 2 (18% +/- 7% vs 28% +/- 8%; p = 0.001; normal limit = 28% to 45%); however, there was no significant difference in area shortening between time 1 and time 2 (49% +/- 10% vs 53% +/- 8%; normal limit = 45% to 65%). We conclude that the preterm newborn infant has distorted left ventricular shape and abnormal wall motion, which alter measurements of shortening fraction and persist for the first weeks of life. Area shortening may be necessary to assess left ventricular performance during the first weeks of life in the premature infant.

Yersinia enterocolitica: a frequent seasonal stool isolate from children at an urban hospital in the southeast United States

From 1 December 1988 through 28 February 1991, 7,290 rectal swab specimens received in our laboratory were screened for Yersinia enterocolitica. A total of 76 patients had Y. enterocolitica isolated from their stool samples. Of these patients, 59 (77.6%) were 12 months old or younger. Y. enterocolitica was second only to Salmonella spp. in this age group. Routine screening for Y. enterocolitica may be warranted in hospitals serving large pediatric populations.

Hyperendemic shigellosis in the United States: a review of surveillance data for 1967-1988

In 1988, 22,796 Shigella isolates were reported to the Centers for Disease Control, the highest number since national surveillance was begun in 1967. From 1986 to 1988, isolation rates increased from 5.4 to 10.1 per 100,000 persons. Increased isolation of Shigella sonnei, primarily among children and young women, occurred throughout the United States in a manner similar to the nationwide increase that occurred during the early 1970s. The highest rates during 1987-1988 were reported from countries with relatively high proportions of urban, ethnic ethnic minority, and poor residents, groups traditionally at high risk. The greatest percentage increases in isolation rates, however, occurred in relatively wealthy counties with predominantly white residents. Between 1967 and 1988, the proportion of Shigella species isolated from persons greater than or equal to 20 years of age increased 118%, while the proportion of the resident population in this age group increased only 16%. These data indicate a shift toward increased infection at older ages and the potential for periodic hyperendemic rates of shigellosis nationwide, which may be due to changing levels of immunity to S. sonnei.

An outbreak of shigellosis at an outdoor music festival

In August 1988, an estimated 3,175 women who attended a 5-day outdoor music festival in Michigan became ill with gastroenteritis caused by Shigella sonnei. Onset of illness peaked 2 days after the festival ended, and patients were spread throughout the United States by the time the outbreak was recognized. An uncooked tofu salad served on the last day was implicated as the outbreak vehicle (odds ratio = 3.4, p less than 0.0001). Over 2,000 volunteer food handlers prepared the communal meals served during the festival. This large foodborne outbreak had been heralded by a smaller outbreak of shigellosis among staff shortly before the festival began and by continued transmission of shigellosis from staff to attendees during the festival. S. sonnei isolated from women who became ill before, during, and after the festival had identical antimicrobial susceptibility patterns and plasmid profiles. Limited access to soap and running water for handwashing was one of the few sanitary deficits noted at this gathering. This investigation demonstrates the need for surveillance and prompt public health intervention when Shigella infections are recognized in persons attending mass outdoor gatherings, the singular importance of handwashing in reducing secondary transmission of shigellosis, and the potential for explosive outbreaks when communal meals are prepared by large numbers of food handlers.

Yersinia enterocolitica O:3: an emerging cause of pediatric gastroenteritis in the United States. The Yersinia enterocolitica Collaborative Study Group

After an outbreak of Yersinia enterocolitica infections among black children in Atlanta, a seven-hospital study was conducted to determine the importance of this pathogen in other communities with large black populations. Of 4841 stool specimens from patients with gastroenteritis examined between November 1989 and January 1990, Y. enterocolitica, Shigella, Campylobacter, and Salmonella were identified in 38, 49, 60, and 98 specimens, respectively; 34 (92%) of 37 Y. enterocolitica isolates were serotype O:3. Of the 38 patients with yersiniosis, 37 (97%) were children. Illnesses were clustered around the holidays, and 20 (62%) of 32 patients had been exposed to raw pork intestines in the 2 weeks before onset. Exposure was significantly associated with illness in a case-control study of eight patients identified at one hospital (P = .004). Infants less than or equal to 6 months old with yersiniosis were more likely to have immature-to-total neutrophil ratios greater than 0.50 than were infants of comparable age with salmonellosis (P = .02). Infrequently isolated in the past, Y. enterocolitica O:3 is emerging as an important enteric pathogen in this country, particularly among black children.

IgG subclasses in the serum and skin in subacute cutaneous lupus erythematosus and neonatal lupus erythematosus

IgG subclasses differ in their biologic and chemical properties, such as complement fixation, protein and cellular binding, and placental transfer. In this study, IgG subclasses of anti-Ro/SSA antibodies in subacute cutaneous lupus (SCLE) and neonatal lupus (NLE) are examined in the serum and in the skin. IgG subclasses in NLE beginning in utero (NLE-heart disease) are compared to subclasses in NLE beginning after birth (NLE-skin disease). Human skin was grafted onto athymic mice, mice were injected with one of eight anti-Ro/SSA maternal NLE sera (four heart block, four skin disease) or seven anti-Ro/SSA SCLE sera, and grafts were examined for IgG subclasses using monoclonal anti-human IgG subclass reagents in an immunofluorescent technique. Lesional skin was examined from four SCLE patients. IgG1 was the only IgG subclass detected in the grafts and skin lesions. IgG1 was the predominant anti-Ro/SSA IgG subclass detected in SCLE and NLE sera in an ELISA using a synthetic Ro/SSA polypeptide. These studies show that the maternal anti-Ro/SSA autoantibodies in NLE-heart disease sera are predominantly IgG1 and are therefore likely to be present in the fetus at the time of gestation, when heart block usually develops. Second, differences in the clinical presentations of NLE (in utero vs. postnatal disease) cannot be attributed to differences in anti-Ro/SSA IgG subclasses. Finally, the subclass bound in the skin in SCLE is IgG1, a subclass capable of mediating tissue injury via complement or cellular effectors.

Maternal autoantibodies and pregnancy--II: The neonatal lupus syndrome

NLE is manifested most typically as transient subacute cutaneous lupus lesions or isolated complete congenital heart block. Babies with NLE have maternal anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies. It is presumed, but not proven, that transmission of these autoantibodies through the placenta to the baby has resulted in disease. However, other factors such as inflammatory cells or complement activation may be necessary for disease to be expressed. About half of babies reported with NLE have had heart disease and about half have had skin disease. There have been a few reports of liver disease and a few of thrombocytopenia. Any combination of these findings is possible in a given infant. Possibly, other haematologic abnormalities, pneumonitis or neurological disease could occur, but the evidence that these other abnormalities are part of NLE is scant. Mortality in NLE has occurred in babies with severe cardiac disease. It is estimated that 10% or more of babies with cardiac NLE die in infancy. Of the remainder, perhaps half will require permanent pacemaker implantation. Thus, there is substantial morbidity and mortality with cardiac NLE. The skin disease, by contrast, is not serious and typically leaves little or no residua. Individuals who have had NLE may develop connective tissue disease in adulthood. Whether this is a common or an unusual occurrence is not yet known, since a large cohort of individuals with NLE has not yet been followed into adulthood. Mothers of babies with NLE are often initially asymptomatic. With time, they frequently develop connective tissue disease symptoms. In our experience, these have been largely symptoms of Sjögren's syndrome and have generally not been debilitating. Most babies of mothers with anti-Ro/SSA, anti-La/SSB, or anti-U1RNP autoantibodies do not develop NLE. There is no way to determine prospectively which fetus or infant will be affected and which of those affected will have life-threatening disease. Systemic therapies should be reserved for those infants who have life-threatening manifestations of NLE. It is not yet known whether treatment of the mother during gestation will be beneficial or harmful to fetuses with severe NLE cardiac disease.

A major autoepitope is present on the amino terminus of a human SS-A/Ro polypeptide

A human SS-A/Ro antigen is present on the polypeptide component of a particle composed of hyRNA and a 60 kD protein. We have now purified the Wil-2 cell 60 kilo dalton (kD) SS-A/Ro protein and determined its amino-terminal amino acid sequence. A synthetic peptide corresponding to residues 7 to 24 of this sequence (RoSP7-24) exhibited enzyme-linked immunosorbent assay (ELISA) binding activity with immunodiffusion-defined, monospecific anti-SS-A/Ro sera. In addition, ELISA binding of monospecific anti-SS-A/Ro sera to native SS-A/Ro antigen was partially inhibited (35%) by KLH-RoSP7-24. Sera from patients known to frequently produce precipitating anti-SS-A/Ro antibody (subacute cutaneous lupus erythematosus [SCLE], 56 patients; Sjögren's syndrome [SS], 41 patients; mothers of infants with neonatal LE [NLE], 10 individuals; infants with congenital heart block [CHB], 5 patients) were tested for reactivity to RoSP7-24 in ELISA. Overall, 38% of SCLE sera, 36% of SS sera, 50% of maternal NLE sera and 20% of CHB infant sera had anti-RoSP7-24 binding levels greater than 2 standard deviations above the mean of that of normal individuals. Of the sera which had anti-SS-A/Ro detected by double immunodiffusion and/or counterimmunoelectrophoresis, 68% of SCLE patients, 71% of SS patients, 55% of NLE mothers and 20% of CHB infants had significantly elevated RoSP7-24 ELISA binding levels. These findings strongly suggest that a major autoepitope of native human SS-A/Ro resides on the amino terminal portion of the Wil-2 SS-A/Ro 60 kD polypeptide.(ABSTRACT TRUNCATED AT 250 WORDS)