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Vol 17 n° 3

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LABORATORY STANDARDS IN THE DIAGNOSIS AND THERAPY MONITORING OF SYSTEMIC LUPUS ERYTHEMATOSUS

Prof. Sándor Sipka, M.D., Ph.D.
3rd Department of Medicine, Institute for Internal Medicine, Medical and Health Science Center, University of Debrecen, Hungary


9.1 Introduction

Systemic lupus erythematosus is the classic type of polysystemic autoimmune diseases. Lupus arises when the immune system mistakenly produces antibodies that attack the body's own tissues, including the kidneys, skin and brain. The causes of the attack are complex, and the impairment of all the main cell types of immunoregulation, T, B, dendritic cells and phagocytes are involved in this process.

The current criteria of the diagnosis are consisting of both clinical and laboratory parameters, as follows:

  • Malarrash (a rash, often butterfly-shaped, over the cheeks)
  • Discoid rash (a type involving red raised patches)
  • Photosensitivity (reaction to sunlight in which a skin rash arises or worsens)
  • Nose or mouth ulcers, typically painless
  • Nonerosive arthritis (which does not involve damage to the bones around the joints) in two or more joints
  • Inflammation of the lining in the lung or heart (also known as pleuritis or pericarditis)
  • Kidney disorder marked by high levels in the urine of protein or of abnormal substances derived from red or white blood cells or kidney tubule cells
  • Neurological disorder marked by seizures or psychosis not explained by drugs or metabolic disturbances (such as an electrolyte imbalance)
  • Blood disorder characterized by abnormally low concentrations of red or white blood cells or platelets (specifically, hemolytic anemia, leukopenia, lymphopenia or thrombocytopenia) and not caused by medications
  • Positive test for antinuclear antibodies not explained by drugs known to trigger their appearance
  • Positive test for antibodies against double-stranded DNA, Sm or certain phospholipids or a false positive result on a syphilis test.

9.2 The pathogenesis of SLE

SLE is a multifactorial disease induced by environmental factors in patients with certain type of genetic and hormonal backgrounds.
HLA-A1, HLA-B8, HLA-DR3 genotype and C4A*Q0 complotype are the main factors of genetic predisposition for SLE.
It is a fundamental clinical observation that in the induction of SLE the role of one or more provoking factors can be recognized in every case, for example, sunlight, infections (mostly viral infections like Epstein Barr virus), hormonal, mainly oestrogen effects (the gender dependent occurrence of disease: female/male = 9/1), in addition some drugs (hydralazine and procainamid).

Though a great variety of the defects in the various signal transduction and apoptosis pathways has been described in the immunocompetents cells of SLE patients, the main problem is the loss of tolerance toward the autoantigens (the impairment of immunoregulatory T cells) and the abundant production of pathologic autoantibodies leading to tissue and organ destructions all over the body. These antibodies are of IgG type with high affinity to the autoantigens, in contrast to the "physiological" autoantibodies of IgM character and with low affinity to autoantigens and being harmless toward the tissues. 

From pathological point of view all autoimmune diseases - included SLE- are special types of inflammations induced by the direct tissue damage elicited by autoreactive cells or antibodies, or by the release of various mediator substances from the white cells accumulated on the damaged area. Therefore, the results of some common laboratory tests can already give information to orient toward the diagnosis of SLE.

 

9.3. The common laboratory tests of inflammation used in the diagnosis of SLE  

Table1. Changes in the results of common laboratory tests

Blood cells

White cell count

Number of neutrophils

Number of lymphocytes

Number of monocytes

Number of erythrocytes (hemoglobin)

Sedimentation of erythrocytes (We)

accelerated

Serology

IgG, IgA, IgM

­

Complement factor 3 (C3)

Complement factor 4 (C4)

Complement activity (CH50)

C reactive protein

­

Transferrin

Immunocomplex

­

Cryoglobulin

appears in association with vasculitis

 

9.4 Measurement of circulating cytokines in patients with SLE

The increased activity of CD3+ CD4+ (ic. IL-2, IL-12, IFNγ positive) Th1 "helper" cells results in elevated serum levels of IL-1β, IL-2, IL-12, TNFα and IFN α and IFNγ. On the other hand, IL-4, IL-6, IL-8, IL-10 and IL-13 are the products of CD3+ CD4+ (ic. IL-4, IL-8, IL-13 positive) Th2 "helper" cells. Whereas SLE is a disease with Th1 dominance, the measurement of IL-2 and INFγ may have a diagnostic importance. Cytokine changes measured in a patient with acute SLE treated with a high dose of glucocorticosteroid are presented in the following observation gained in our laboratory:

Table 2.Changes in serum levels of circulating cytokines in a patient with acute SLE after glycocorticosteroid treatment

Type of cytokine

Serum levels (pg/ml)

before steroid

after steroid

Interleukin 2

8.15

50.2

Interleukin 4

0.75

9.42

Interleukin 10

30.42

63.55

Interferong

69.8

51.4

 

9.5 Changes in the peripheral distribution of lymphocytes in SLE

Flow cytometry gives the chance to determine the various subsets of peripheral lymphocytes. In addition to the above mentioned two subsets of T "helper" cells (Th1 and Th2), it is worth measuring the CD8+ "cytotoxic" , CD19+ "antibody producing" B and CD56+ "natural killer" cells. CD3+HLA-DR+ lymphocytes represent the "late" type, whereas the CD3+CD69+ cells the "early" types of "activated" T cells. The three forms of regulatory T lymphocytes (Treg cells) are the following:

a) CD3+CD4+(ic. TGFβ positive) Th3 cells,
b) CD3+CD4+ (ic. IL-10 positive) Tr1 cells,
c) CD3+CD25+ (Foxp3 positive) suppressor T cells.

Table 3. Changes in lymphocyte subsets

Lymphocyte subsets

Change

CD3+ T cell

CD4+ T cell (helper cell)

CD8+ T cell (cytotoxic cell)

­

CD56+ (natural killer cell)

­

CD3+ HLADR+ ("late" activated T cell)

­

CD3+ CD69+ ("early" activated T cell)

­

CD3+ CD4+ (ic. IL-2, IFN g+) Th1 T cell

­

CD3+ CD4+ (ic. IL-4, IL-6+) Th2 T cell

CD3+ CD4+ (ic. TGF b+) Th3 T cell

­ (in fibrosis)

CD3+ CD4+ (ic. IL-10+) Tr1 T cell

­

CD4+ CD25+ suppressor regulative T cell

 

9.6 The types and occurrence of pathological autoantibodies in SLE

The serological verification of the various "marker" autoantibodies of SLE is the most important task of the laboratory for the diagnosis of SLE. This is a fundamental part of work proving the "autoimmune" background of the disease, furthermore, giving the chance to monitor the efficacy of therapy and to demonstrate the potential coexistence of an other autoimmune disease in a form of "overlap syndrome". We use to say that for the laboratory diagnosis of SLE it is crucial to verify one of the "marker" antibodies in the patient at least once.

The "antinuclear autoantibodies (ANA)" and "antiphospholipid autoantibodies" are forming the majority of "marker" antibodies of SLE.

Antinuclear autoantibodies (ANA or "antinuclear factor" ANF)

Antigens:  double stranded (ds) DNA,
         extractable nuclear antigens, Sm ( U1 RNP)
         nucleosome (chromatine): mixture of DNA + histone (H2A, H2B, H3, H4)
         molecules    
         nucleoplasma and nucleomatrix antigens : SS-A, SS-B.
 
Laboratory detection:
          IF, ELISA, immunoblotting.


Antiphospholipid autoantibodies

Antigens: cardiolipin
        β2 -glycoprotein I
        lupus anticoagulans

Laboratory detection:
        ELISA: RIA for cardiolipin and β2 glycoprotein I (IgG and IgM antibodies)
        APTI measurement for the detection of lupus anticoagulans (prolongation).

9.7       Occurrence (per cent) of the most important autoantibodies in the sera of SLE patients

1.

*Anti-double stranded DNA (anti-dsDNA)

60-70 %

2.

Anti-histone (H1, H2A, H2B, H3, H4)

40-60

3.

*Anti- nucleosome (anti- chromatine)

85-90

4.

*Anti-Sm

30-35

6.

Anti-U1RNP

 20-25

7.

Anti-SS-A  

40-50

8.

Anti-SS-B

20-25

9.

PCNA

1-5  

10.

Anti-ribosomal P protein

12-16

11.

Rf

1-5

12.

*Antiphospholipid (anti-cardiolipin and anti-b2 glycoprotein I)

40-50

13.

ANCA

 

14.

Anti-erythrocytes

 

15.

Anti-thrombocytes

 

16.

Anti-endothelium

 

17.

Anti-C1q

 

 

*Marker antibodies of the disease

9.8 Additional useful laboratory measurements for the diagnosis of SLE

Serological tests:

a.   Complement measurements (C3, C4, CH50 - decrease)
b.   C3a and C5a (increase)
b.  Acut phase proteins (CRP - increases)
c.  Circulating immunocomplexes (increase)
d.   DNase activity (decreases)
 

9.9 Interpretation of pathological laboratory data in SLE

a) Pathological laboratory results supporting the diagnosis:

   Serological tests:
            Anti-ds - DNA
            Anti- Sm
            Anti-nucleosome (anti-chromatine)
            Anti- phospholipid IgG (mainly anti-β2 glycoporotein I)
            Decrease in C3, C4, CH50
            Increase in C3a and C5a
            Increase in CRP level and We (erythorocyte sedimentation)
  
    Cellular tests:
            Leukopenia
            Lymphopenia
            Thrombocytopenia
            Decrease in the number of CD4+CD25+ suppressor T cells
            Decreased activity and production of superoxide anions by phagocytes 
LE cell positivity (atypic granulocytes phagocytosing apoptotic nucleic fragments)

     Urinary tests:
            Proteinuria
            Cylindruria  
  

b) Pathologic laboratory results reflecting the activity of SLE

      Serological tests:
                  High level of anti-ds-DNA
                  Hypocomlementaemia
                  Increase in the level of C5a 
                  Increase in the level of circulating immunocomplexes
                  Increased erythrocyte sedimentation 
     
Cellular tests:
                   High degree of leuko/lymphopenia
                   Great decrease in the number of CD4+CD25+ suppressor T cells


c) Laboratory results reflecting successful therapy of SLE

     Serological tests:
                 Decrease in the level of anti-ds-DNA
                 Increase in the level of C3, C4 and in the value of CH50
                 Decrease in the level of C5a
                 Decrease in the level of circulating immunocomplexes
                 Decrease in erythrocyte sedimentation
   
     Cellular tests:
                 Increase in the number of leukocytes/lymphocytes
                 Increase in the number of CD4+ CD25+ suppressor T cells


d) Antibodies reflecting subtypes of SLE or associations with other autoimmune diseases (overlaps)

        anti-SS-A: association with Sjögren syndrome (or cardiac block in neonates)
        anti-histone: drug induced SLE       
        anti-phospholipid: antiphospholipid syndrome
        p-ANCA/ anti-C1q: lupus nephritis
        anti-ribosome P protein: SLE with psychiatric syndromes
        cryoglobulin: SLE with vasculitis

9.10 Autoantibodies in "healthy" subjects

The specificity and sensitivity of laboratory tests applied for autoantibody determinations is strongly depend on the dilution of sera used for the measurements. It is recommended that all antibody determinations (especially the immunofluorescence measurements) should be concurrently carried out in the serum dilutions of 1:40 and 1:160. It also has to be mentioned that after infections some antimicrobial antibodies can crossreact with the autoantigens of nuclear type used in the in vitro assays of autoantibody determinations. These are positive reactions from laboratory point of view, but totally irrelevant from the clinical aspect of autoimmune diseases. Therefore, the close contact between the clinicians and laboratory specialists is very important in the common interpretation of clinical and laboratorial data.

9.11 The current principles of successful therapy of SLE

  • Diagnosis in the earliest time (optimal co-operation between clinics and laboratory).
  • Early starting of the most effective immunosuppression in order to prevent the occurrence of irreversible damages in the various organs.

List of abbreviations

ANA = antinuclear antibodies; ANCA = antineutrophil cytoplasmic antigen; ANF = antinuclear factor = ANA; APTI = activated partial thromboplastin time; CD = cluster defined; CRP = C reactive protein; DNA = deoxyribonucleic acid; DNase = deoxyribonuclease; ELISA = enzyme linked immunusorbent assay; HLA = human leukocyte antigen; ic = intracytoplasmic; IF = indirect immunofluorescence; IFNγ = interferon γ; IL = interleukin; PCNA = proliferating cell nuclear antigen; RIA = radioimmunoassay; Rf = rheumatoid factor; SLE = systemic lupus erythematosus; TGFβ = transforming growth factor β

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