Serology Quiz #2

ANA Test

• screening test for autoantibody reactivity

• uses cells in diff stages of mitosis as substrate

• reacts with DNA/RNA of substrate cells

Homogeneous pattern

anti-dsDNA, anti-ssDNA, histones = SLE

Centromere pattern (discrete speckled)

CREST

Speckled pattern

extractable nuclear Ag = SLE, RA, Sjogren

Nucleolar pattern

anti-nucleolar RNA = scleroderma, sjogren, SLE

Confirmatory test for SLE

Crithidia luciliae

high sensitivity of Hep-II substrate and relative specificity of high binding for ssDNA

SLE

negative ANA = rules out SLE

specific for SLE = anti-dsDNA and anti-Sm

antiSSA Ags = neonatal SLE syndrome

drug-induced SLE: milder form of lupus with homogenous ANA pattern

Sjogren’s syndrome

HLA-C, HLA-DR3

autoantibodies = 90% rheumatoid factor

definitive diagnosis: biopsy of labial salivary gland

Scleroderma

2 forms of disease: progressive diffuse and systemic CREST

• Calcinosis - bone formation

• Raynaud - vasoconstriction of hands/feet

• Esophageal involvement

• Sclerodactyly - skin on fingers harden

• Telangiectasia - spider veins

Lab findings

• centromere pattern

• nucleolar pattern

Insulin-dependent diabetes mellitus

deficient insulin production due to immune destruction of B cells in pancreas

HLA-DR3, HLA-DR4, HLA-DQw8

Mixed connective tissue disease

diffuse tissue disease that doesn’t fall in one disease category

ANA: 50% low titer RF/ high titer of anti-RNP, anti-ssDNA

distinguish from SLE with absence of multiple anti-SM and anti-dsDNA

Rheumatoid arthritis

IgG, IgM, IgA found in synovium, blood, connective tissue

plasma cells secrete IgG RF

circulating immune complexes consist of immunoglobulins, complement, RF

ANA: 14-28% of pts

RA latex agglutination detects mostly IgM RF

Hashimoto’s thyroiditis

94% have titer of 1:100 of anti-thyroid microsomal Ab

Graves disease

TSI thyroid stimulating immunoglobulins bind to thyroid cells and stimulate thyroid activity

GI Tract disease

Pernicious anemia: atrophy of gastric mucosa —> inability to secrete HCl and intrinsic factory (IF) —> no IF present to bind vitamin B12 —> megaloblastic anemia

86% have Abs against gastric parietal cells lipoprotein cytoplasmic component

Liver disease

70% have ANA mixture of speckled, homogeneous, anticentromic, nuclear membrane patterns

diagnosis: presence of auto Abs, no anti-dsDNA

• anti-liver soluble protein, anti-liver membrane. anti-acidoglycoprotein receptor

Inflammatory bowel disease

ANCA (anti-neutrophilic cytoplasmic antibody)

Hepatitis

anti-smooth muscle

Biliary cirrhosis

anti-mitochondrial

Goodpasture’s disease

anti-glomerular basement membrane

Prenicious anemia

anti-parietal cell

Multiple myeloma

autoimmune disorder of CNS —> formation of lesions in white matter of brain and spinal cord resulting in destruction of myelin sheath

Myasthenia gravis

antibody-mediated damage to acetylcholine receptors in skeletal muscles

Serum protein electrophoresis (SPE)

Immunofixation electrophoresis (IFE)

determine what immunoglobulin abnormalities present

Complement system testing

heat liable = inactivated by heating at 56C for 30min

Total hemolytic complement (CH50) assay

• screening test for function of classical system based on ability of patient’s complement to lyse standarized amount anitbody coated sheep RBCs

Sensitivity

proportion of individuals with the disease who test positively with the test

high sensitivity = few false positives

Specificity

proportion of individuals without disease who test negatively for disease

high specificity = few false positives

Serological titers

titers are indicators of strength of an antibody response

Precipitation reactions

soluble antigen reacts with soluble antibody to produce insoluble Ag/Ab complexes

• Ag/Ab complexes formed at high rate can be measured for turbidity using turbidimetric or nephelometry

Radial immunodiffusion (RID)

pt IgG diffuses across agar to zone of equivalence and precipitin ring is formed and measured

standard curve based on diameter of precpitin ring vs conc

Immunofixation electrophoresis (IFE)

separation of proteins into discrete bands

Immunoelectrophoresis (IEP)

separation of proteins as Ab is placed in a trough running parallel to electrophoresis

• diffusion of Ag&Ab and precipitin arc formed

Latex agglutination

particulate test Ags that have been absorbed onto latex beads react with Abs

Hemagglutination test

RBCs in viral testing

Flocculation tests

precipitate of fine particles that is microscopic or macroscopic

Complement fixation test

uptake of complement indicator of Ag/Ab formation

• lack of hemolysis indicates complement reacted with Ag/Ab complex

• hemolysis indicates complement not fixed into Ag/Ab complex and there are not Ab