Anti-chromatin and anti-histone antibodies in Egyptian patients with systemic lupus erythematosus
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- Shabana, A.A., El-Ghawet, A.E., Machaly, S.A. et al. Clin Rheumatol (2009) 28: 673. doi:10.1007/s10067-009-1130-2
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There has been a renewed interest in anti-chromatin and anti-histone antibodies in the last few years. To assess the prevalence of anti-chromatin and anti-histone antibodies in patients with systematic lupus erythematosus (SLE) and to correlate serum levels of these antibodies with clinical features of the disease, the presence of anti-chromatin and anti-histone antibodies in 38 patients with SLE was investigated by an enzyme-linked immunosorbent assay (ELISA). To determine the specificity of these antibodies, 15 patients with rheumatoid arthritis, 15 patients with systemic sclerosis, and 15 normal controls were also tested. Sensitivity of anti-chromatin antibodies in SLE patients was 89.5% and specificity was 80.0%, while sensitivity of anti-histone antibodies was 92.1% and specificity was 82.2%. Significant associations were found between the levels of anti-chromatin antibodies and arthritis, malar rash, oral ulcer, pulmonary affection (P < 0.05) also, lupus nephritis (P < 0.01), and disease activity score as measured by SLE disease activity index (SLEDAI; P < 0.001). Significant association was found between anti-histone antibodies and fatigue (P < 0.05). The incidence of positive anti-chromatin and anti-histone antibodies was significantly higher than that of anti-dsDNA antibodies in early stage of the disease. We conclude that anti-chromatin and anti-histone antibodies are both sensitive and specific for SLE and could be a useful addition to the laboratory tests that can help in the diagnosis of SLE. Anti-chromatin antibodies seem to be a promising marker useful in early diagnosis and assessment of disease activity in SLE patients especially in patients who are negative for anti-dsDNA antibodies.
KeywordsAnti-chromatin antibodiesAnti-histone antibodiesSLE
Systemic lupus erythematosus (SLE) is the most diverse of the autoimmune diseases and it is characterized by the production of multiple auto-antibodies. Today, the spectrum of auto-antibodies detected in SLE is wide and complex . Although anti-dsDNA antibodies are considered the main diagnostic tool for SLE and may be a useful marker of disease activity; however, they are found only in 50% of SLE patients and do not always correlate with disease activity . On the other hand, antinuclear antibodies, the most prevalent antibodies, have low specificity for the diagnosis of SLE because they are found in most systemic autoimmune diseases and even in healthy individuals. Thus, it is important to look for other auto-antibodies that may be useful in the diagnosis and assessment of the disease activity in SLE patients .
The aim of this study was to assess the prevalence of anti-chromatin and anti-histone antibodies in patients with SLE and to correlate their serum levels with clinical features of the disease.
Materials and methods
This study was carried out on 68 patients in addition to 15 apparently healthy subjects as control group. All were selected from the outpatient clinics of Rheumatology and Rehabilitation Department, Mansoura University Hospital.
- Group I:
included 38 female patients with SLE, according to the American Rheumatism Association (ARA) revised criteria for the classification of SLE .
- Group II:
included 15 female patients with RA, according to the American Rheumatism Association Criteria for the classification of RA .
- Group III:
included 15 female patient with SSc, according to American Rheumatism Association Criteria for the classification of (SSc) .
- Group IV:
included 15 apparently healthy females.
Age and disease duration among the studied groups
Group I SLE (n = 38)
GroupII RA (n = 15)
Group III Sc (n = 15)
Group IV Control (n = 15)
Mean ± SD
25.0 ± 9.25
38.3 ± 10.9
34.2 ± 8.5
26.9 ± 5.4
Disease duration (years)
Mean ± SD
3.3 ± 3.2
6.7 ± 6.3
3.8 ± 1.8
All patients were subjected to the following:
Through history taking, physical examination; including general examination, systemic examination, and examination of locomotor system. Assessment of disease activity in SLE patients was performed using the SLE Disease Activity Index (SLEDAI) .
The following investigations were performed; plain X-ray for the affected joints, plain X-ray chest, electrocardiogram for suspected cases of cardiac affection, electromyography and nerve conduction velocity for suspected cases of nerve and muscle affection, fundus examination, and kidney biopsy from cases with nephropathy which was considered when patients presented with (a) persistent proteinuria >0.5 g/day or greater than 3+ if measurement was not performed; or (b) cellular casts or (c) otherwise unexplained rise in serum creatinine >75 mmol/l. Renal biopsies were categorized according to the modified classification proposed by the WHO .
The following laboratory investigations were performed to all patients and controls: complete blood picture, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), serum creatinine, liver transaminase; AST, ALT, complete urine analysis for; proteinuria, RBCs, WBCs, casts, and a quantitative 24-h urine examination for albumin. Estimation of complement components C3 and C4 in serum using radial immunodiffusion technique. Quantitative detection of antinuclear antibody (ANA) and anti-dsDNA antibody in the serum detected by ELISA. Serum level of anti-chromatin and anti-histone antibodies were detected by ELISA.
Using QUANTA lite TM chromatin which is an enzyme-linked immunosorbent assay (ELISA) for the semi-quantitative detection of chromatin antibodies and histone antibodies in human serum. The cut off value of anti-chromatin was above 20 IU/ml and for anti-histone was above 1 IU/ml.
Data obtained from the present study were computed using SPSS versions 11.5 under the platform of Microsoft Windows. Continuous data were expressed in the form of mean ± SD while categorical data were expressed in the form of count and percent. Comparison of continuous data was performed utilizing Student t test if between two groups for parametric quantitative data or one-way ANOVA if among more than two means, while comparison of categorical data was done using Chi-square test. For association between clinical manifestations and anti-chromatin antibodies, a logistic regression test was performed for multivariate analysis to rule out possible confounding variables using anti-chromatin antibodies as the dependant variable. Relation between variables was investigated by Spearman's correlation coefficient. P value less than 0.05 was considered statistically significant.
Prevalence of SLE clinical manifestations
Positive blood levels of ANA were detected in 37 patients (97.4%), while positive levels of anti-dsDNA were detected in 27 (71%) among SLE patients. Positive levels of anti-chromatin antibodies were detected in all patients with disease duration less than 1 year (100%) and were detected in 23 patients with disease duration more than 1 year (85.1%). Positive levels of anti-dsDNA antibodies were detected in seven patients with disease duration less than 1 year (63.6%) and were detected in 20 patients with disease duration more than 1 year (74%). The incidence of anti-chromatin antibodies was significantly higher (P < 0.01) than that of anti-dsDNA antibodies in the initial stage of the disease.
There were significantly higher levels of anti-chromatin antibodies titer in patients with arthritis, malar rash, oral ulcer and pulmonary affection than those without (P < 0.05 for all) while this significant association was found between the level of anti-histone antibodies titer and fatigue (P < 0.05) but not any of the other clinical manifestations. SLEDAI scores of SLE patients positively correlated with serum levels of anti-chromatin antibodies (P < 0.001), and did not significantly correlate with serum levels of anti-histone antibodies (P > 0.05). On the other hand, no significant correlations were observed between anti-chromatin and anti-histone antibodies and any of the hematological parameters in SLE patients.
Renal biopsy was done in 14 patients who showed significantly higher serum levels of anti-chromatin antibodies (P < 0.01) than patients without nephritis. Furthermore, there was significant correlation between serum levels of anti-chromatin antibodies (P < 0.01) and WHO renal biopsy classes. While, no significant difference was observed between serum levels of anti-histone antibodies in patients with and without renal involvement and consequently no significant correlation between serum levels of anti-histone antibodies and renal biopsy class was found. When regression analysis was set for multiple variables, only renal involvement and arthritis were showing statistical significance in the multivariate analysis.
The clinical features of our SLE patients were similar to previously published data from other cohorts [3, 11–21] (see also supplementary material). The high percentages of increased levels of anti-chromatin and anti-histone antibodies titers detected in our SLE patients, were closely similar to what had been reported previously [19, 22–24], while other studies detected lower percentages varying from 64% to 75% [11, 14, 25–28]. It was surprising to find a high rate of positivity of anti-chromatin and anti-histone antibodies among RA patients (33.3% and 20%, respectively) in contrast to others [27, 29]; meanwhile this high positivity rate in our SSc patients (26.7% and 33.3%, respectively) goes with previous studies [23, 30] and lower in one study . However, this may be due to the small sample size. Significantly higher levels of anti-chromatin and anti-histone antibodies titers have been reported in SLE patients rather than other autoimmune and connective tissue disorders including RA and SSc [3, 11, 14, 24, 25, 27].
Sensitivity and specificity of anti-chromatin and anti-histone antibodies for diagnosis of SLE in our study, were found to be (89.5%, 80%) and (92.1%, 82.2%) respectively which was similar to what was reported in the literature [29, 32–35], although, they were lower in other studies [22, 27, 36]. Some of these studies showed interestingly conflicting results considering anti-histone antibodies as a highly specific marker for SLE with a diagnostic value comparable to anti-dsDNA  while others considered it to be sensitive but non-specific for SLE, although reporting lower sensitivity and specificity (55%, 69% respectively) and can be also detected in other autoimmune and non-autoimmune diseases . These differences may be explained by many factors: the various antigen substrates used especially their degree of purification compared with non-histone proteins; the procedures used to select the cutoff value; the ability to detect low levels of antibody; and, additionally, differences between patients cohorts, may go part of the way to explain disparities in the prevalence and specificities of antibodies cited in various reports.
In this work, anti-chromatin antibodies were significantly detected during the first year of the disease more than anti-dsDNA. This was in agreement with some earlier  and also more recent studies  who detected anti-chromatin antibodies in all SLE patients with recent onset and in murine models of lupus before appearance of anti-dsDNA and more even in SLE patients who were negative for anti-dsDNA [34, 35]. The SLEDAI score of our SLE patients was strongly positively correlated with serum levels of anti-chromatin but not anti-histone antibodies as previously reported [3, 19, 25]. This could increase the utility of applying anti-chromatin antibodies as a promising useful marker for diagnosing SLE at early stage and detecting disease activity status.
Significant associations were found between the level of anti-chromatin antibody titer and some clinical features in our SLE patients such as arthritis, malar rash, oral ulcers, pulmonary affection and renal involvement. These results were parallel with the findings of others [3, 27]. However these associations were all weak and when regression analysis was set for multiple variables only renal involvement and arthritis were showing statistical significance in the multivariate analysis, the same as found by Cervera et al . When compared with patients with other autoantibodies, it was reported that patients with anti-histones had a lower incidence of several clinical and laboratory features of SLE [19, 39] which was the case in our study.
Many authors have reported significant correlation between serum levels of anti-chromatin antibodies and lupus nephritis [3, 8, 11, 14, 26, 27, 29, 40–43] while others have found this correlation with anti-histone antibodies . Meanwhile, some authors failed to report such association with either anti-chromatin  or anti-histone antibodies [25, 37]. This association seems to depend on a complex interaction between charges associated with the quaternary structure of the nucleosomes and epitope targets in renal tissue  and that immune complexes comprising chromatin and anti-chromatin antibodies can deposit in the glomerular basement membrane of the kidney .
Anti-chromatin and anti-histone antibodies are both sensitive and specific for SLE and could be a useful addition to the laboratory tests that can help in the diagnosis of SLE. Determination of anti-chromatin antibodies could be a promising useful parameter for early diagnosis of SLE patients and moreover assessment of their disease activity status. Furthermore, its increased titer appears to be a sensitive marker for identifying patients with lupus nephritis.