Antinuclear antibodies in the relatives of patients with systemic sclerosis

Evaluation of multiplexed fluorescent microsphere immunoassay for detection of autoantibodies to nuclear antigens

Antibodies to extractable nuclear antigens (ENA) are found in a variety of collagen vascular diseases. Determining the individual specificities of these antibodies is extremely useful in establishing the disease diagnosis and in some cases the prognosis. With a multiplexed fluorescent microsphere immunoassay, reactivity to five of the most diagnostically useful ENA was measured in 249 serum samples, including samples from 56 patients previously documented to have systemic lupus erythematosus (SLE). Results of the multiplexed assay were compared to results from established ENA enzyme-linked immunosorbent assays (ELISAs), and the agreement, sensitivity, and specificity, respectively, for the five ENA evaluated were as follows: SSA, 99.1, 100.0, and 98.8%; SSB, 98.6, 88.9, and 99.5%; Sm, 97.6, 95.8, and 97.9%; RNP, 97.2, 92.7, and 98.8%; Scl-70, 93.6, 50.0, and 99.0%. In the 56 confirmed SLE patients, the frequency of significant concentrations of autoantibodies with the multiplexed assay was 21.4% for SSA, 7.1% for SSB, 10.7% for Sm, 32.1% for RNP, and 0% for Scl-70. The new flow cytometric bead-based multiplexed assay showed excellent correlation with the well-established single-analyte ELISA methods for four of five the ENA markers investigated in this study. The most notable discrepancies between the two assays were for the Scl-70 antigen, which was most often resolved in favor of the multiplexed assay. Our studies show that the multiplexed microsphere-based immunoassay is a sensitive and specific method for the detection and semiquantitation of ENA antibodies in human sera.

The clinical relevance of autoantibodies in scleroderma

Scleroderma (systemic sclerosis) is associated with several autoantibodies, each of which is useful in the diagnosis of affected patients and in determining their prognosis. Anti-centromere antibodies (ACA) and anti-Scl-70 antibodies are very useful in distinguishing patients with systemic sclerosis (SSc) from healthy controls, from patients with other connective tissue disease, and from unaffected family members. Whereas ACA often predict a limited skin involvement and the absence of pulmonary involvement, the presence of anti-Scl-70 antibodies increases the risk for diffuse skin involvement and scleroderma lung disease. Anti-fibrillarin autoantibodies (which share significant serologic overlap with anti-U3-ribonucleoprotein antibodies) and anti-RNA-polymerase autoantibodies occur less frequently and are also predictive of diffuse skin involvement and systemic disease. Anti-Th/To and PM-Scl, in contrast, are associated with limited skin disease, but anti-Th/To might be a marker for the development of pulmonary hypertension. Other autoantibodies against extractable nuclear antigens have less specificity for SSc, including anti-Ro, which is a risk factor for sicca symptoms in patients with SSc, and anti-U1-ribonucleoprotein, which in high titer is seen in patients with SSc/systemic lupus erythematosus/polymyositis overlap syndromes. Limited reports of other autoantibodies (anti-Ku, antiphospholipid) have not established them as being clinically useful in following patients with SSc.

Test performance in systemic sclerosis: anti-centromere and anti-Scl-70 antibodies

PURPOSE

To determine the sensitivity and specificity of anti-centromere (ACA) and anti-Scl-70 antibodies in systemic sclerosis (SSc).

METHODS

Four-hundred ninety-seven English language articles published from 1966 to 1994 were identified by structured MEDLINE search. Articles in which either ACA or anti-Scl-70 antibodies were measured in both SSc patients and a non-SSc control group were reviewed and rated using a previously published diagnostic testing scale. Reported sensitivity and specificity from each study was converted into a 2 x 2 table, and combined across studies to calculate summary rates for each antibody. Author's clinical classification criteria for SSc served as the gold standard for disease diagnosis.

RESULTS

In 30 articles that fulfilled inclusion criteria, ACA were found in 441 of 1,379 SSc patients (sensitivity 32%, range 17% to 56%). This increased to 57% (332 of 585) in patients with the limited cutaneous, or CREST, subset of SSc (IcSSc). Anti-Scl-70 antibodies were found in 366 of 1,074 SSc patients (sensitivity 34%, range 3% to 75%), and this increased slightly to 40% in patients with the diffuse cutaneous form of SSc (dcSSc). Both antibodies were measured in 670 patients, and either test was positive in 58% (range 29% to 86%), but in only 3 patients were both antibodies present. The specificity of each antibody was high, but varied by control group. ACA were present in 5% and anti-Scl-70 antibodies were present in 2% of patients with other connective tissue diseases, but fewer than 1% of disease free controls had either antibody present.

CONCLUSIONS

As individual diagnostic tests in SSc, both ACA and anti-Scl-70 antibodies are highly specific. Each performs somewhat better as discriminators of clinical subsets for patients in whom a diagnosis of SSc has already been established. Clinicians can rely on a positive test result as being specific in the detection of disease, but 40% of SSc patients are likely to have neither antibody present, and a negative result does not exclude the diagnosis. Measurement of these antibodies should be considered secondary to the clinical features when making a diagnosis of SSc.

Serum concentrations of basic fibroblast growth factor in collagen diseases

BACKGROUND

Basic fibroblast growth factor (bFGF), a cytoplasmic polypeptide growth regulator that induces endothelial cell and fibroblast proliferation, is produced by endothelial cells and skeletal muscle.

OBJECTIVE

We hypothesized that this factor is involved in fibrotic changes in muscle and skin in collagen diseases.

METHODS

The serum level of bFGF was measured in 74 patients with systemic sclerosis, 12 with systemic lupus erythematosus, 33 with dermatomyositis, 13 with Raynaud's disease, and 20 control subjects.

RESULTS

bFGF was undetectable in the serum of normal persons, but detectable levels were found in 31 of 74 patients with systemic sclerosis and 7 of 33 patients with dermatomyositis. Elevated serum bFGF level was correlated with an elevated plasma endothelin level and anticentromere antibody in patients with systemic sclerosis. An elevated serum bFGF level correlated with lung fibrosis and an elevated creatine kinase level in the patients with dermatomyositis.

CONCLUSION

Measurement of the serum bFGF level may be useful to detect vascular damage in patients with systemic sclerosis and muscule fibrosis in patients with dermatomyositis.

Serum tissue inhibitor of metalloproteinases in patients with systemic sclerosis

BACKGROUND

One of the suggested contributory factors to the development of dermal fibrosis is a decrease in collagenase activity, which may be related to levels of serum tissue inhibitors of metalloproteinase-1 (TIMP-1).

OBJECTIVE

The aim of this study was to determine the clinical significance of serum TIMP-1 levels in systemic sclerosis (SSc).

METHODS

We measured serum TIMP-1 concentration in 62 patients with SSc, 11 patients with systemic lupus erythematosus, 14 patients with rheumatoid arthritis, and 22 members of a normal control group. The clinical features of the patients with SSc and elevated TIMP levels were examined.

RESULTS

The mean TIMP-1 level in the patients with SSc was significantly higher than that in the members of the control group or the patients with systemic lupus erythematosus or rheumatoid arthritis. In 44% of the patients with SSc the serum TIMP-1 level was elevated. The mean serum TIMP-1 level in patients with diffuse cutaneous SSc (dSSc) was significantly higher than that in those with limited cutaneous SSc. The patients with dSSc and elevated serum TIMP-1 levels showed a significantly greater incidence of lung fibrosis and anti-topoisomerase I antibody than those with normal serum TIMP-1 levels. The TIMP-1 level and diffusing capacity for carbon monoxide in the patients with SSc were negatively correlated. Increased mitogenic activity on dermal fibroblasts caused by serum from patients with dSSc was partially blocked by anti-TIMP-1 IgG.

CONCLUSIONS

These findings suggest that serum TIMP-1 level is a useful indicator of disease activity in patients with SSc and that TIMP is involved in the pathogenesis of SSc.

Demonstration of interleukin-2, interleukin-4 and interleukin-6 in sera from patients with localized scleroderma

Localized scleroderma has been reported to be accompanied by immunological abnormalities related to B cells, but little is known about T-cell activation in this disease. In this study, serum levels of interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-6 (IL-6), which are known to be released by activated T cells, were determined using a sensitive enzyme-linked immunosorbent assay in 48 patients with localized scleroderma and 20 with systemic sclerosis, and in 20 healthy control subjects. IL-2, IL-4 and IL-6 were detected in serum from patients with localized scleroderma but not in that from healthy controls. The presence of antihistone antibodies correlated significantly with elevated IL-4 and IL-6 levels. Decreased serum levels of IL-2, IL-4 and IL-6 paralleled improvement in cutaneous sclerosis. Frequent detection of these lymphokines in serum from patients with localized scleroderma reflects T-cell activation in this disorder.

Comparison of three commercially available enzyme immunoassays for the screening of autoantibodies to extractable nuclear antigens

The initial screening test used in the diagnosis of connective tissue diseases is based on the detection of antinuclear antibodies (ANA) by indirect immunofluorescence (IFA). When the ANA screen is positive, it is often useful to determine the specificity of the autoantibody to a series of extractable nuclear antigens (ENA), a procedure that has been classically performed by double immunodiffusion. Testing large numbers of clinical specimens for autoantibodies to ENA by double diffusion techniques can be time-consuming and expensive. ENA screening systems that employ enzyme immunoassay (EIA) technology have recently become commercially available. We compared three EIA ENA assays to classic Ouchterlony double diffusion techniques. Furthermore, the sensitivity of each antigen and methodology (including ANA immunofluorescence using HEp-2 cells) was tested using ENA positive sera possessing single autoantibodies. Two of the three EIAs that detected immunoglobulin G type autoantibodies to Smith (Sm), ribonucleoprotein (RNP), Sjögren's syndrome-associated antigens Ro (SSA) and La (SSB), were provided by INOVA and Sigma Diagnostics. A third EIA, which also included scleroderma-associated antigen 70 (SCL-70/DNA-topoisomerase I) and histidyl-tRNA synthetase (Jo-1) in addition to the four previously stated antigens, was provided by Clark Laboratories. This latter ENA screen detected IgG, IgA, and IgM type autoantibodies. Included in the study were sera covering a wide variety of anti-nuclear and other autoantibodies. Sensitivity was 100% for all EIA ENA screens when compared to Ouchterlony double diffusion and specificity exceeded 95% in each case. Sensitivity studies showed Ouchterlony to be less sensitive than EIA when detecting low levels of autoantibodies to ENA.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiology of systemic sclerosis

Systemic sclerosis is a family of disorders most appropriately considered in the category of the connective tissue diseases. Two major forms are recognized (diffuse cutaneous and limited cutaneous involvement subtypes), each with distinctive clinical and serologic findings as well as natural history. Scleroderma is characterized epidemiologically by several distinctive features. From a demographic viewpoint, the disease spares children and its incidence increases steadily with age among adults. If occurs much more frequently in women, especially during the child-bearing years, and most often and most severely in young black women, though there is no overall prominent racial predilection. The annual incidence approaches 20 per million population, and may be considerably underestimated. Both incidence and mortality have increased during the past several decades, but these changes are most likely a result of improved case detection rather than a true increase in incidence. Prevalence studies have not been undertaken, but 500 per million population may be a reasonable estimate. Family and genetic studies suggest a weak genetic predisposition, but several strong HLA associations with scleroderma-specific serum autoantibodies are evident. Certain environmental agents may be implicated in pathogenesis of scleroderma and closely related systemic illnesses associated with cutaneous fibrosis. The widespread pathologic process in systemic sclerosis leads to vascular insufficiency and fibrosis, which diminishes the reserve function of many organ systems. The result is considerable disability, especially affecting hand function, and a significant reduction in life span, with an overall 10-year survival from first physician diagnosis of under 70%. Further epidemiologic studies should take full advantage of established and newly proposed subsets of patients with homogeneous clinical, laboratory, serologic, and natural history features. The environment-host interactions noted here must be fully explored, especially in early untreated disease, where primary rather than secondary mechanisms are most likely to be operative.

Serum concentration of procollagen type I carboxyterminal propeptide in systemic sclerosis

The serum level of procollagen type I carboxyterminal propeptide (P1CP), which has been used as an index of collagen synthesis in patients with various fibrotic diseases during the active stage, was measured using enzyme-linked immunosorbent assay in 61 patients with systemic sclerosis (SSc) and in 21 control subjects. The mean P1CP level in the SSc patients was significantly higher than in the normal controls (mean +/- SD, 326 +/- 319 vs 128 +/- 87 ng/ml; p < 0.005). In 36% of the SSc patients, the serum P1CP level was significantly elevated more than two standard deviations above the mean control value. The mean serum P1CP level in patients with diffuse SSc was significantly higher than in those with limited SSc (411 +/- 373 vs 255 +/- 199 ng/ml; p < 0.05). In addition, the SSc patients with elevated serum P1CP levels showed a significantly greater incidence of lung fibrosis and joint involvement than those with normal P1CP levels (p < 0.005 and p < 0.05, respectively). These results suggest that the serum P1CP level is a useful indicator of the severity of disease in SSc patients.

Immunologic parameters in systemic sclerosis

BACKGROUND

Immunologic abnormalities seem to play an important role in important role in systemic sclerosis (SSc).

METHODS

We studied the following immune parameters to get more insight into SSc: autoantibodies (antinuclear antibodies (ANA), anti-Scl-70, anticentromere antibodies (ACA) subsets of lymphocyte subpopulations and markers of their activation, as well as serum levels of IL-2, the soluble IL-2 receptor (SIL-2R), IL-6 and its correlation to N-terminal procollagen-III propeptide (P III P), and finally, the IL-6 production by SSc and normal dermal fibroblasts.

RESULTS

In patients with active SSc, we found a reduced number of CD2+ T-lymphocytes and an increase in the expression of T-lymphocyte activation markers such as CD25+ and CD71+, HLA-DR Ia, as well as elevated serum levels of SIL-2LR and IL-6. SSc fibroblasts did not produce more IL-6 than normal fibroblasts in monolayer cultures.

CONCLUSIONS

Our data show that a wide range of immunologic parameters are altered in SSc. In general, T-helper (TH) lymphocytes are activated possibly because of reduced T-suppressor (TS) and natural killer (NK)-cell levels. TH may polyclonally stimulate B cells, which in turn produce higher amounts of autoantibodies. Our findings support the concept that TH cell-derived cytokines/growth factors stimulate matrix protein synthesis by fibroblasts, resulting in generalized fibrosis.

Autoantibodies against topoisomerase I detected with the natural enzyme and overlapping recombinant peptides

Antibodies against topoisomerase I (anti-topo I, anti-Scl-70) are regarded as a marker of systemic sclerosis. The various frequencies of anti-topo I detected in those patients depends at least in part on the test design and the kind of the antigen used. We therefore analyzed three overlapping recombinant topo I fragments (N-terminal, center and C-terminal part of the molecule) covering the full length of the enzyme for substitution of highly purified natural antigens (n-topo I) in ELISA for antibody screening. 49 of 50 sera reacting with n-topo I in ELISA also recognized the recombinant C-terminal topo I fragment under identical test conditions, 37 sera recognized the recombinant center and two sera the recombinant N-terminal peptide. All sera reactive with the N-terminal and center peptide reacted with the recombinant C-terminus which therefore may substitute for the natural antigen. In immunoblot assays 92% (46/50) of the sera reacted with n-topo I and 86% (43/50) with the recombinant C-terminal peptide. Immunoblots therefore seem to be less sensitive for detecting anti-topo I antibodies than ELISA regardless the source of the antigen used. In a screening of 696 sera submitted for routine antibody tests the recombinant peptide ELISA on the other hand detected two sera which did not react with n-topo I in ELISA. Because of the high rate of agreement within the results obtained with the two antigens, n-topo I can be substituted by the recombinant peptide ELISA allowing better standardization and interlaboratory comparison of results.

Systemic sclerosis

Systemic sclerosis affects the connective tissue of various organs. It is characterized by alteration of the microvasculature with a dense inflammatory cellular infiltrate, followed by massive deposition of collagen. This review discusses diagnostic criteria, clinical subsets, survival data, clinical evaluation, epidemiology, pathogenesis, immunobiology, genetics, and therapy for systemic sclerosis in adults. Because the diagnosis of systemic sclerosis is most dependent on its cutaneous involvement, knowledge of this is essential in the evaluation and management of patients with this disorder.

Diagnostic significance of nailfold bleeding in scleroderma spectrum disorders

BACKGROUND

The early detection of scleroderma spectrum disorders (SSD) is important.

OBJECTIVE

Our purpose was to determine the prevalence of nailfold bleeding in SSD.

METHODS

We examined patients for nailfold bleeding in the following three groups: (1) 81 patients with SSD including 50 patients with scleroderma, 10 with mixed connective tissue disease, and 21 with Raynaud's phenomenon having specific antinuclear antibody (ANA); (2) 99 patients with other connective tissue diseases or primary Raynaud's phenomenon; and (3) 200 patients with common skin diseases.

RESULTS

The frequency of nailfold bleeding was significantly higher in SSD (75.3%) than in other connective tissue diseases (12.1%) and in controls (3.0%). The presence of nailfold bleeding in two or more fingers showed a 98.3% specificity for SSD. Among the patients with SSD, the incidence of nailfold bleeding in scleroderma, mixed connective tissue disease, and Raynaud's phenomenon with specific ANA was similar. Nailfold bleeding strongly correlated with the presence of anticentromere antibody.

CONCLUSION

The presence of nailfold bleeding is useful for the early detection of SSD.

Clinical evaluation of scleroderma spectrum disorders using a points system

We have established a new diagnostic method using a points system to evaluate patients with early scleroderma and those with scleroderma spectrum disorders (SSD). To examine the clinical usefulness of this method, it was applied to a total of 215 cases including 97 patients with scleroderma, 32 with SSD, 28 with presumed primary Raynaud's phenomenon (RP) and 58 with other connective tissue disorders (CTD). A total score was obtained for each patient as the sum of the following five factors: (1) extent of skin sclerosis (maximum, 10 points); (2) pulmonary changes (maximum, 4 points); (3) antinuclear antibodies (maximum, 5 points); (4) pattern of Raynaud's phenomenon (maximum, 3 points); and (5) nailfold bleeding (maximum, 2 points). Of the 97 scleroderma patients, 86 (89%) had 9 or more points, and of the 32 SSD patients, 28 (88%) had 5 to 8 points. In contrast, all patients with presumed primary RP and 54 of 58 (93%) patients with other CTD had 0 to 4 points. These data suggest that this diagnostic method is very useful not only for clinical evaluation of SSD, but also for the differentiation of scleroderma and SSD from other CTD and primary RP.

The effects of scleroderma sera on endothelial cell survival in vitro

The effects of sera and of platelet-poor plasma from patients with scleroderma on endothelial cell survival in vitro were studied. The survival ratio of rat heart endothelial cells was studied both in 10% test serum and in 10% platelet-poor plasma. Sera from patients with scleroderma decreased the survival ratio significantly when compared with sera from normal controls. In contrast, there was no significant difference between platelet-poor plasma from patients with scleroderma and that from normal controls. Our data indicate that platelets in the patients with scleroderma may cause vascular damage by affecting endothelial cell survival.

Are ACA and Scl 70 antibodies mutually exclusive?

Serological studies using indirect immunofluorescence, double immunodiffusion and immunoblot with recombinant Topo I and kinetochore antigens were performed in 180 patients with systemic scleroderma. In the sera of 10 patients, we found coexisting ACA and Scl 70 antibodies, and this was confirmed by all three methods. The relationship between the coexistence of these antibodies and the clinical features of the disease is not clear, although in all these cases there was pronounced vascular involvement.

Antikinetochore and antitopoisomerase I antibodies in systemic scleroderma: comparative study using immunoblotted recombinant antigens, immunofluorescence, and double immunodiffusion

In 135 patients with systemic scleroderma, we compared three different methods to determine antinuclear autoantibody (ANA) specificity: indirect immunofluorescence, double immunodiffusion, and, employing recombinant antigens, immunoblotting using both marker autoantigens of this disease. A characteristic Scl-70 antibody pattern was found on HEp-2 cells in 83.8% of the patients, double immunodiffusion was positive for the Scl-70 antibodies in 81.9%, and immunoblot with the recombinant topoisomerase I (Topo I) was positive in 71% of the patients. For the centromere autoantibodies we found a high concordance between the anticentromere antibody (ACA) pattern on HEp-2 cells (27 patients positive) and the detection of recombinant kinetochore in immunoblotting (26 patients positive). The three testing techniques gave comparable results, except that the Topo I recombinant antigen used in immunoblotting reacted strongly with fewer than expected of the known Scl-70-positive sera. However, a method using recombinant antigens expressing all epitopes (rather than one of the epitopes of Topo I) will undoubtedly become the method of choice for detecting antibodies in systemic scleroderma. Using the immunoblotting technique with the recombinant antigens we detected in four patients antibodies against both Topo I and kinetochore. More severe symptoms of systemic scleroderma were found in patients who had both antibodies. The combined presence of both marker autoantibodies is therefore not as rare as previously reported and may predict severe disease.

Antinuclear antibodies detected by indirect immunofluorescence on HEp2 cells and by immunoblotting in patients with systemic sclerosis

The HEp2 cell cultures appeared highly sensitive in detecting the antinuclear antibodies (ANAb) in systemic sclerosis, principally anticentromere antibodies of the CREST syndrome. The immunoblotting used with either complex cellular extracts from HeLa and rabbit thymus or purified nuclear components (high mobility group (HMG) proteins and histones) is able to identify precisely the ANAb targets and to contribute to diagnosis. With nuclear extracts of HeLa cells, the sera from 75.8% of CREST syndrome subjects stained 18 and 22 kD proteins. Corresponding antibodies were also detected in 72.7% of these patients, on HEp2 centromers by indirect immunofluorescence. With the same extracts, 33.3% of sera from diffuse sclerosis/acrosclerosis patients contain antibodies staining 86, 73, 32 and 30kD. These sera also stain 77, 66 and 63kD from thymus extracts. Corresponding antibodies will be the anti-SCL-70 antibodies defined by double immunodiffusion. The anti-HMG antibodies were infrequent in systemic sclerosis, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) and consequently without interest for diagnosis. The anti-whole histones antibodies which are less frequent in diffuse sclerosis/acrosclerosis (35.7%) than in SLE (41.3%) recognize especially H1 and H2A in the first diseases, H1 and H2B in SLE and H1 and H3 in RA.

Lymphocytotoxic autoantibodies in progressive systemic sclerosis

In 53 patients with progressive systemic sclerosis (PSS) the lymphocytotoxic activity of their serum was measured in a microlymphocytotoxicity assay. In 21 of the 53 patients the test reacted distinctly positively in the heterologous system, and in 9 of these 21 also in the autologous system. After preparation of the immunoglobulins from these positive sera, whole cytotoxic activity was detected only in the IgM fraction but not in the IgG fraction. When using prepared T lymphocytes as target cells in the microlymphocytotoxicity test, the cytotoxic activity of the positive PSS sera showed itself to be directed against this lymphocyte population. Further analysis using the Western-blot technique showed that the IgM autoantibody in PSS sera reacted with the cell surface of CD4+ lymphocytes. The cross reactivity with extractable nuclear antigens was rather improbable. These results suggest that lymphocytotoxic autoantibodies may play a role in immunological disturbances in PSS.

Familial clustering of scleroderma spectrum disease

This is the second case report of familial scleroderma (systemic sclerosis) in South Carolina. The family includes two cases of scleroderma meeting American Rheumatism Association criteria, one of systemic sclerosis sine scleroderma, and two other cases of undifferentiated connective tissue disease with features of scleroderma spectrum disorders; there are also two cases of Raynaud's phenomenon (one associated with rheumatoid arthritis), for a total of seven affected relatives. Evidence of scleroderma spectrum disorders was sought in six siblings of the two co-index cases and in 23 of the 35 offspring. Laboratory studies included antinuclear antibody determinations and typing for the following genetic markers: HLA (A, B, C, DR), complotypes, Gm and Km allotypes, and alpha-1 antitrypsin phenotypes. No common genetic markers restricted to affected members of this family were found, and no environmental exposures were detected that could explain this familial clustering of cases. This report should, however, add to the slowly accumulating information on the genetic characteristics of families at unusually high risk for scleroderma spectrum disorders. Positive antinuclear antibody tests at a titer of 1/40 or higher were present in 57 percent of the first-degree relatives of the affected cases.

Antinuclear antibodies in the relatives and spouses of patients with systemic sclerosis

The families of 65 patients with systemic sclerosis were examined clinically and serum samples from each subject were tested for antinuclear antibodies (ANA) by immunofluorescence on HEp2 cells and for precipitating antibodies to soluble cellular antigens including Scl-70. Of 217 blood relatives, 58 (27%) had ANA (42 speckled, 13 nucleolar, one centromere, two homogeneous); 22 (10%) had precipitins, one anti-Scl-70, one anti-PM-Scl, one anti-nRNP, two anti-Ro(SSA), the remainder unidentified). Family members tended to share ANA patterns. Of 38 spouses, nine (24%) had ANA (all speckled) and two showed unidentified precipitins. This compares with an incidence of ANA and precipitins in a control population of 8% and 1% respectively. Antibodies were more common in female than male relatives (particularly in mothers and sisters of probands). Twenty one of the 58 family members with ANA had clinical features of connective tissue disease; the remainder were asymptomatic. The presence of genetic factors influencing autoimmunity is suggested by the incidence of autoantibodies in first degree relatives. Similar observations in spouses, however, indicate that environmental factors may also have a role in these immune abnormalities.

Scl 70 antibody--a specific marker of systemic sclerosis

Scl 70 antibodies were tested for in 107 patients with systemic sclerosis: 68 with acrosclerosis and 39 with diffuse scleroderma. Anticentromere antibodies (ACA) and other antinuclear antibodies (ANA) were tested for by indirect immunofluorescence on HEp-2 cells. Positive results for Scl 70 antibodies were obtained in 77% of cases of diffuse scleroderma and 44% of acrosclerosis. ACA and Scl 70 antibodies were found to be mutually exclusive. If acrosclerosis cases positive for anticentromere antibodies are excluded, the percentage of acrosclerosis cases positive for Scl 70 was 63%. ACA were found to be a marker of a benign, abortive subset of acrosclerosis with almost no cutaneous involvement (CREST), whereas Scl 70 did not discriminate between acrosclerosis and diffuse scleroderma. On HEp-2 cells Scl 70 positive sera gave a characteristic, fine speckled, almost homogeneous nuclear staining pattern.

Anti-nuclear RNP antibodies in two sisters

Two sisters with clinical elements of mixed connective tissue disease were found to have anti-nuclear RNP (nRNP) antibodies. These antibodies were not found in the six other family members examined. The sisters had inherited an identical HLA haplotype A2-Bw61-Cw3-DR1 from their mother who had had Raynaud's phenomenon for several years. Analysis of peripheral lymphocyte subsets in the patients and their immediate relatives showed decreased OKT-4-positive cells in one of the patients and increased OKT-8-positive cells in both patients, their father and their brother, resulting in lower OKT 4/OKT 8 ratios in these members of the family. This is the third description of the familial occurrence of anti-nRNP antibodies and it adds further evidence for the implication of genetic factors in the development of anti-nRNP antibodies.