Spectrum of Autoantibodies in Systemic Lupus Erythematosus

Slide 1 · Spectrum of autoantibodies

in systemic lupus erythematosus

Diagnostic patterns · pathogenic mechanisms · clinicopathologic correlations

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning outcomes

Classify SLE autoantibodies by target and pathogenic mechanism.

Interpret HEp-2 immunofluorescence patterns and antigen-specific confirmation.

Relate anti-dsDNA, anti-Sm, anti-Ro/La, and antiphospholipid antibodies to clinical findings.

Explain immune-complex injury, cytopenias, and the amplification of autoimmunity.

Slide 3 · SLE is defined by heterogeneous autoimmunity

Antinuclear antibodies are the most characteristic laboratory hallmark.

Targets extend beyond the nucleus to circulating proteins, blood cells, and cellular compartments.

Immune complexes and antibody binding to cells cause much of the tissue injury.

The serologic profile contributes to diagnosis and clinicopathologic interpretation.

Slide 4 · Autoantibody targets occupy distinct compartments

Nuclear

DsDNA · chromatin · Sm · U1-RNP

Ro / La

SS-A and SS-B nucleoproteins

Plasma / membrane

Phospholipid–protein complexes

Blood cells

Erythrocytes · leukocytes · platelets

Slide 5 · Autoantibodies injure by more than one mechanism

Autoantibodies + self antigens

Soluble or deposited immune complexes

Cell-reactive antibodies

Opsonization and cell destruction

Antiphospholipid antibodies

Prothrombotic clinical phenotype

Slide 6 · Diagnostic specificity differs sharply among antibodies

Sensitive screening

Generic ANA

Frequent in SLE but also detectable in other autoimmune conditions.

Disease-associated specificity

Anti-dsDNA and anti-Sm

High diagnostic specificity; Anti-dsDNA also linked to nephritis.

Slide 7 · Major SLE autoantibodies: Approximate positivity

Antibody

Positive in SLE

Main association

Generic ANAs

95–100%

Not specific for SLE

Anti-dsDNA

40–60%

Nephritis; SLE specific

Anti-Sm

20–30%

SLE specific

Anti-U1-RNP

30–40%

Ribonucleoprotein reactivity

Anti-Ro/La

30–50%

Neonatal lupus / congenital heart block

Antiphospholipid

30–40%

Antiphospholipid syndrome association

Approximate ranges reproduced Table 6.10; Positivity varies by population and assay.

Slide 8 · Anti-dsDNA links serology and renal injury

Antibody target

DsDNA

Targets double-stranded DNA, a nuclear self antigen.

Relatively specific for SLE compared with generic ANAs.

Associated with nephritis; DNA–anti-DNA immune complexes may deposit in glomeruli.

Interpret serology alongside urinary findings, complement, and the clinical picture.

Slide 9 · Anti-Sm identifies an SLE-associated nuclear antigen

Antibody target

Sm

Recognizes Smith proteins of small ribonucleoprotein particles.

Reported in a minority of SLE patients (approximately 20–30%).

Highly specific association with SLE; Absence does not exclude SLE.

May be suggested by coarse speckled HEp-2 nuclear fluorescence.

Slide 10 · U1-RNP illustrates antigen overlap across diseases

Antibody target

U1-RNP

Recognizes U1 ribonucleoprotein within the nuclear RNA-processing machinery.

Present in a substantial subset of patients with SLE.

Coarse speckled ANA staining may accompany anti-U1-RNP.

An antigen-specific result must be interpreted with the clinical phenotype.

Slide 11 · Anti-Ro/La connects maternal antibodies with fetal effects

Antibody target

Ro / La

Ro/SS-A and La/SS-B are nucleoprotein autoantigens.

These antibodies with neonatal lupus and congenital heart block.

A positive result is clinically relevant beyond the patient’s current organ symptoms.

The maternal and fetal clinical contexts determine the significance.

Slide 12 · Antiphospholipid antibodies target protein complexes

Antibody target

APL

The antigenic targets are plasma proteins interacting with phospholipids, not simply naked phospholipid.

Examples discussed include β2-glycoprotein I and prothrombin.

These antibodies are present in approximately 30–40% of patients with SLE.

Only a subset of antibody-positive patients develop clinical antiphospholipid syndrome.

Slide 13 · Generic ANAs are not equivalent to SLE

What positivity indicates

Autoimmune reactivity

Nuclear/cellular self-reactivity may support a broader diagnostic assessment.

What it does not establish

Disease identity

Generic ANA alone is not specific enough to establish SLE.

Slide 14 · A single antibody result must not replace clinicopathology

Clinical phenotypes vary widely because multiple organ systems may be involved.

Antibody specificity provides evidence, not a complete clinical diagnosis.

The accompanying morphology, blood counts, urinary findings, and complement state add context.

Distinguish a classification rule from the clinical act of diagnosing a patient.

Slide 15 · HEp-2 indirect immunofluorescence: Basic assay

Patient serum

Incubate with cultured HEp-2 cells

Bound autoantibodies

Add fluorescent anti-human immunoglobulin

Fluorescent signal

Read cellular localization and pattern

Slide 16 · HEp-2 IFA detects more than nuclear structures

Nucleus

Chromatin and nuclear proteins

Nucleolus

RNA-processing components

Cytoplasm

Ribosomal proteins or mitochondria

Mitotic apparatus

Cell-cycle-associated structures

Slide 17 · The fluorescence pattern is a clue, not proof

Autoantigens occupy characteristic subcellular sites and create recurring patterns.

More than 30 ICAP patterns in a classification hierarchy.

A pattern provides a presumptive antigen family rather than a confirmed specificity.

Use an antigen-specific assay to identify the antibody implicated by a pattern.

Slide 18 · Homogeneous nuclear pattern

Diffuse nuclear fluorescence suggests antibodies to chromatin, dsDNA, or sometimes histones.

This pattern as common in SLE.

The same visual pattern does not identify a single unique autoantibody.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 19 · Coarse speckled nuclear pattern

Variable-sized intranuclear speckles suggest ribonucleoprotein reactivity.

Commonly associated with Sm and U1-RNP antibodies.

Can occur in SLE as well as other connective tissue diseases.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 20 · Fine speckled nuclear pattern

Numerous small, evenly distributed intranuclear speckles.

Frequent pattern but of low diagnostic specificity.

Requires clinical correlation and directed antigen-specific testing.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 21 · Peripheral nuclear envelope pattern

Emphasis at the nuclear envelope rather than diffuse nucleoplasm.

May reflect anti-gp210, anti-p68, or anti-lamin reactivity.

Points toward additional autoimmune disease contexts, not specifically SLE.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 22 · Nucleolar patterns favor a different disease spectrum

Homogeneous, clumpy, and punctate nucleolar patterns reflect different antigen families.

Examples include Th/To, fibrillarin/U3-RNP, and RNA polymerase I.

At high titer, nucleolar patterns suggest systemic sclerosis more than typical SLE.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 23 · Centromere pattern localizes to discrete nuclear foci

Associated with centromeric proteins CENP-A, CENP-B, and CENP-C.

More characteristic of systemic sclerosis and certain other autoimmune disorders.

Can occur occasionally in SLE; Morphology alone is not diagnostic.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 24 · Cytoplasmic reticular pattern suggests mitochondria

Cytoplasmic reticular staining corresponds to mitochondrial structures.

Associated with reactivity to pyruvate dehydrogenase E2.

Serves as a differential clue toward primary biliary cholangitis.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 25 · Cytoplasmic dense fine speckles have distinct targets

Can reflect antibodies to ribosomal P proteins (P0, P1, P2), which are specific for SLE.

Alternatively, antibodies against tRNA synthetases can produce related cytoplasmic staining.

Pattern recognition must be followed by antigen-specific discrimination.

Schematic fluorescence distribution — not a HEp-2 micrograph

Slide 26 · Interpret fluorescence in three sequential levels

Localization

Nuclear · nucleolar · cytoplasmic

Pattern

Homogeneous · speckled · rim · discrete foci

Specific antigen

Confirm with an appropriate immunoassay

Slide 27 · HEp-2 IFA and antigen assays serve different roles

HEp-2 IFA

Broad screening

Shows the spatial pattern of reactivity across many cellular targets.

Antigen-specific assay

Specificity confirmation

Tests a selected antigen; Can resolve a suggested antibody identity.

Slide 28 · Multiplex tests require clinical targeting

Solid-phase platforms use purified, recombinant, or extracted cellular antigens.

Multiplex panels can examine several relevant specificities in one clinical scenario.

Their role is complementary to fluorescence pattern assessment.

Avoid inferring a complete antibody spectrum from any single limited antigen panel.

Slide 29 · Autoantibody panels are interpreted as patterns of evidence

Result or pattern

Suggests

Does not itself prove

Generic ANA positive

Broad self-reactivity

SLE as a specific disease

Anti-dsDNA positive

SLE-associated specificity

Active nephritis without clinical data

Anti-Sm positive

Specific SLE association

That all organ manifestations are present

Antiphospholipid positive

Prothrombotic antibody class

Clinical thrombosis or obstetric syndrome

Coarse speckled IFA

Sm/U1-RNP family possible

The precise antigen identity

Slide 30 · Blood-cell-directed autoantibodies explain cytopenias

Antibody binds a blood cell

Erythrocyte, leukocyte, or platelet

Opsonization

Phagocytic recognition and removal

Reduced cell count

Anemia, leukopenia, or thrombocytopenia

Slide 31 · Antiphospholipid complexes reveal cryptic epitopes

Phospholipid surface

A platform for associated plasma proteins

Bound protein

Newly exposed or configured epitopes

Specific autoantibody

Protein–phospholipid complex recognized

Slide 32 · Lupus anticoagulant: An in-vitro versus in-vivo paradox

In laboratory coagulation tests

Apparent anticoagulation

Some antibodies prolong phospholipid-dependent clotting assays, including PTT.

In patients

Hypercoagulability

These patients can experience venous and arterial thrombosis.

Slide 33 · Why syphilis screening may be falsely positive

Antiphospholipid antibody

Reacts with cardiolipin-associated assay antigen

Serologic cross-reaction

Non-treponemal syphilis test can be positive

Clinical interpretation

Do not equate this signal with confirmed infection

Slide 34 · Antiphospholipid syndrome: Clinical consequences

Venous or arterial thrombosis is a major clinical manifestation.

Recurrent spontaneous pregnancy losses may occur.

Focal cerebral or ocular ischemia can accompany thrombosis.

Antibody positivity alone and the full clinical syndrome are distinct findings.

Slide 35 · Primary and SLE-associated antiphospholipid syndromes

Primary syndrome

No underlying SLE

Clinical antiphospholipid syndrome occurs without an associated systemic disorder.

Secondary syndrome

Occurs with SLE

Similar thrombosis/obstetric manifestations accompany established lupus.

Slide 36 · The first pathogenic step is loss of self-tolerance

Self-reactive clones survive

B-cell and helper T-cell checkpoints fail

Self nuclear antigen persists

Incomplete disposal of nuclear material

Adaptive immune activation

Autoantibody production is sustained

Slide 37 · Genetic risk is polygenic rather than deterministic

Both MHC and non-MHC loci contribute to susceptibility.

Family and twin observations support inherited predisposition.

Multiple associated loci influence lymphocyte signaling and interferon responses.

Environmental and immune factors remain important; No single locus explains most SLE.

Slide 38 · HLA-DQ variation can shape the antibody repertoire

Inherited MHC variation

Selected HLA-DQ alleles

Immune recognition context

Associations with antibody generation

Serologic phenotype

Anti-dsDNA · anti-Sm · antiphospholipid

Slide 39 · Early complement components support immune homeostasis

Inherited C1q, C2, and C4 deficiencies occur in some lupus patients.

Complement supports clearance of immune complexes and apoptotic debris.

Inefficient disposal increases the availability of nuclear self antigens.

Defective complement activity can therefore promote autoimmunity as well as reflect consumption during active disease.

Slide 40 · Inefficient apoptotic-cell clearance increases antigen load

Cell death

Nuclear DNA and nucleoproteins become accessible

Incomplete clearance

Self antigens remain in the extracellular compartment

Immune recognition

Autoreactive lymphocytes encounter persistent targets

Slide 41 · B- and T-cell dysregulation cooperate

B-cell tolerance defect

Autoreactive B cells persist

Central or peripheral deletion and control mechanisms fail.

Helper T-cell response

Antibody maturation supported

CD4+ cells responding to nucleosomal antigens assist autoreactive B cells.

Slide 42 · Nuclear nucleic acids stimulate innate sensors

Immune complex uptake

DNA/RNA-containing complexes enter immune cells

Intracellular TLR engagement

Self nucleic acids act as activating ligands

Reinforced activation

B-cell autoantibodies and dendritic-cell cytokines increase

Slide 43 · Type I interferon amplifies immune activation

Nucleic-acid stimulation

Dendritic cells receive innate signals

Type I interferon production

Antiviral cytokine activity becomes sustained

Immune amplification

B cells, T-cell help, and inflammatory responses may increase

Slide 44 · Ultraviolet exposure supplies a plausible trigger

Ultraviolet irradiation

Promotes cellular apoptosis and altered nuclear material

More self antigen

Increases material available for immune recognition

Local inflammation

Keratinocyte cytokines may accentuate skin injury

Slide 45 · SLE autoimmunity forms a self-amplifying loop

Apoptosis / nuclear-antigen exposure

Autoantibody generation

Immune-complex uptake

TLR and interferon signaling

Positive feedback: Each round can reinforce antigen exposure and autoreactivity

Slide 46 · Most systemic lesions reflect type III hypersensitivity

Self antigen + antibody

Immune complexes form

Tissue deposition

Glomeruli and small blood vessels are vulnerable

Complement activation

Inflammation and tissue injury occur

Slide 47 · Renal immune-complex deposits provide mechanistic evidence

DNA–anti-DNA complexes can be detected in glomerular sites.

Granular immunoglobulin and complement deposits support immune-complex deposition.

Low serum complement can indicate immune-complex-associated consumption.

Renal T-cell infiltrates may contribute additional tissue injury.

Slide 48 · Type II hypersensitivity produces hematologic injury

Type III mechanism

Immune-complex deposition

Damage to glomeruli, vessels, and connective tissues.

Type II mechanism

Antibodies coat cells

Opsonized erythrocytes or platelets are removed by phagocytes.

Slide 49 · Hematoxylin bodies are antibody-reactive nuclear remnants

Damaged cell exposes its nucleus

Nuclear material loses normal chromatin pattern

Autoantibody binds exposed antigen

A homogeneous LE / hematoxylin body forms

Phagocyte engulfs nuclear material

LE cell can be seen; Now chiefly historical

Slide 50 · Neuropsychiatric injury has multiple proposed pathways

Some autoantibodies may cross the blood–brain barrier and bind neuronal targets.

Reactivity to neurotransmitter receptors has been proposed.

Cytokines and vascular pathology may contribute to cognitive or CNS manifestations.

That precise mechanisms remain incompletely defined.

Slide 51 · Organ injury reflects antibody class and location

Kidney

Immune complexes → glomerular injury

Blood

Cell-directed antibodies → cytopenias

Vessels

Immune complexes / aPL → vascular injury

Skin

Immune and inflammatory injury → interface changes

Slide 52 · Small-vessel vasculitis can contain fibrinoid necrosis

Acute necrotizing vasculitis may affect capillaries, arterioles, and small arteries.

Fibrinoid necrosis characterizes active vessel-wall injury.

Chronic lesions may develop fibrous wall thickening and luminal narrowing.

These changes fit an immune-mediated vascular injury mechanism.

Slide 53 · Lupus nephritis is a major immune-complex complication

The kidney may show glomerulonephritis and tubulointerstitial nephritis.

Clinically significant involvement requires attention to proteinuria, hematuria, and casts.

Renal morphology is varied; The detailed nephritis classification is addressed elsewhere.

Antibody findings inform the evaluation but do not replace renal tissue and clinical assessment.

Slide 54 · Lupus skin lesions show interface injury

Vacuolar injury occurs along the basal epidermal layer.

Dermal edema and perivascular inflammation may accompany the rash.

Immunoglobulin and complement may deposit along the dermoepidermal junction.

Epidermis

Dermis

Basal interface injury

Original anatomical schematic — not histology

Slide 55 · The lupus band is not independently disease-specific

What the finding shows

Immune deposition

Immunoglobulin and complement at the dermoepidermal junction.

Interpretive limit

Not exclusive to SLE

Comparable deposition can occur in other connective tissue diseases.

Slide 56 · Articular lupus generally lacks erosive destruction

SLE

Typically nonerosive synovitis

Pain and inflammation can occur with limited structural joint damage.

Rheumatoid arthritis

Erosive arthritis is a key contrast

The morphologic distinction guides the differential diagnosis.

Slide 57 · Serositis translates immune injury into effusions

Serosal inflammation

Pleura or pericardium affected

Acute response

Fibrinous exudate and pain may occur

Chronic remodeling

Thickened fibrous surfaces and adhesions may develop

Slide 58 · Libman–Sacks endocarditis is noninfective

Small verrucous vegetations may involve either surface of valve leaflets.

Mitral and aortic valves are particularly involved.

This is morphologically distinct from typical infective or rheumatic valve vegetations.

Valve leaflet

Small warty deposits

Original valve schematic — not pathology imaging

Slide 59 · SLE activity can deplete circulating complement

Increased immune-complex formation

More complement activation

Complement consumption

Serum levels can decrease

Integrated interpretation

Assess immune activity with clinical manifestations

Slide 60 · Clinical serology must be integrated with organ assessment

Serologic finding

Related clinical question

Corroborating evidence

Anti-dsDNA

Is renal involvement present?

Urinalysis and kidney evaluation

Blood-cell antibodies

Are cytopenias present?

Complete blood count

Antiphospholipid antibodies

Thrombotic phenotype?

Thrombosis / obstetric history

Low complement

Immune complex activity?

Current symptoms and organ findings

Anti-Ro/La

Neonatal/fetal risk context?

Maternal–fetal clinical assessment

Slide 61 · Case: A positive ANA without disease-specific findings

Clinical stem

A patient has a positive generic ANA but no clear multisystem clinical syndrome.

Interpretive question

Question: Does the antibody result alone establish SLE?

Teaching answer

Interpretation: No. Generic ANAs are sensitive but not specific; Phenotype and directed testing are necessary.

Slide 62 · Case: Anti-dsDNA with abnormal urinary findings

Clinical stem

A patient with suspected SLE has anti-dsDNA reactivity and new proteinuria.

Interpretive question

Question: What complication needs targeted evaluation?

Teaching answer

Interpretation: Possible lupus nephritis; Assess renal function, urine sediment, complement, and morphology as appropriate.

Slide 63 · Case: Prolonged PTT and a thrombotic event

Clinical stem

A patient with lupus has a prolonged phospholipid-dependent clotting test and a thrombosis.

Interpretive question

Question: Does “anticoagulant” imply protection against clots?

Teaching answer

Interpretation: No. Antiphospholipid antibodies may prolong in-vitro tests yet coexist with thrombosis.

Slide 64 · Case: Maternal anti-Ro/La reactivity

Clinical stem

Maternal Ro/SS-A or La/SS-B antibodies are identified during pregnancy.

Interpretive question

Question: Which fetal-associated lupus manifestation is important?

Teaching answer

Interpretation: These antibodies with neonatal lupus and congenital heart block.

Slide 65 · Final synthesis: Four decisions for every autoantibody

Target

What cellular or protein complex is recognized?

Specificity

Does positivity identify SLE or merely suggest autoimmunity?

Mechanism

Immune complexes, cytopenias, or prothrombotic state?

Context

Which clinical and morphological findings corroborate it?

Slide 66 · Central concepts to retain

Generic ANA detection is broad; Anti-dsDNA and anti-Sm offer greater SLE specificity.

The HEp-2 pattern proposes a target family, but antigen-specific assays confirm identity.

Immune complexes dominate many organ lesions; Cell-reactive antibodies cause cytopenias.

Antiphospholipid antibodies link abnormal assays with thrombosis, not protection from clotting.

Loss of tolerance, persistent nuclear antigens, TLRs, and interferon sustain the response.

Slide 67 · Source and interpretation boundaries

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th edition (2026). Chapter 6, pp. 197–203.

Topic scope: SLE autoantibodies, ANA staining patterns, immunologic pathogenesis, and clinicopathologic correlations.

Approximate antibody positivity from Robbins Table 6.10; staining-pattern concepts from Figure 6.24 caption and text.

Classification criteria shown in the source are historical; this lecture does not present them as contemporary diagnostic rules.