Autoimmune Diseases

Autoimmune Diseases Henry O. Ogedegbe, PhD., C(ASCP)SC Department of EHMCS

Learning Objectives • Upon completion of these materials the student will be able to: • Describe contributive factors to autoimmune diseases • Distinguish organ specific and systemic autoimmune diseases with examples of each • Describe the effects of SLE on the body • List four types of autoantibodies found in lupus and describe pattern seen in IFA testing • Discuss the symptoms of rheumatoid arthritis • Describe the characteristics of the Abs found in rheumatoid arthritis

Learning Objectives • Differentiate Hashimoto’s thyroiditis and Graves’ disease on the basis of lab findings and immune mechanism • List the main Abs tested for in Graves’ and Hashimoto’s diseases and describe testing procedures • Relate genetic susceptibility to the development of insulin dependent diabetes mellitus • Explain immunologic mechanism known to cause destruction of  cells in insulin-dependent diabetes mellitus • Discuss immunologic findings in multiple sclerosis, myasthenia gravis and Goodpasture’s syndrome

Introduction Introduction • Autoimmune diseases are the result of damage to the body by the presence of autoantibodies or autoreactive cells • About 2% of the population are affected by such diseases • There is a breakdown of self tolerance in these individuals • Self tolerance is brought about by such mechanisms as clonal deletion of relevant effector cells, active regulation by TS cells and regulation through idiotypic networks • Majority of T cells that are processed through the thymus do not survive. Self reactive T cells are destroyed • Loss of TS cells may encourage the production of autoAbs

Introduction • MHC molecules influence Ag recognition or nonrecognition by determining peptide that can be presented to T cells • The expression of class II molecules on host cells may result in presentation of self Ags for which there is no tolerance • In several diseases, there are host cells that exhibit class II molecules on their surfaces after inflammatory response • Such cells may function as Ag presenting cells for their own cellular proteins

Introduction • Genetic variation in MHC Ag may account for increased susceptibility in certain individuals • Idiotypic network may also play a part in autoimmune diseases • This refers to situations whereby antibodies are produced against antibodies • When an Ab is produced for the first time, the variable region may be seen as foreign by the host • The host may then produce antibodies against it • The anti-idiotypic Ab may have reactivity against self Ags

Introduction • Anti-idiotypic Abs are found in diseases such as myasthenia gravis, diabetes mellitus, and Graves’ disease • The anti-idiotypic Abs may mimic the original Ab and combine with the receptor for that Ag • Defects in natural killer cells, in the secretion of ILs, in phagocytosis and complements may also contribute • Hormones especially estrogen have been found to enhance B-cell activation and suppress regulator activities of T cell • Environmental conditions such as infectious agents like viruses, bacteria and drugs contribute to autoimmunity

Systemic Lupus Erythematosus • It is a chronic systemic inflammatory disease marked by alternating exacerbation and remissions • Approximately 1 in every 2000 individuals are affected • Age of onset is usually b/w 20 and 40 yrs of age • Women are much more likely than men to be stricken by a margin of 13 to 1 • Etiology is unknown but may be due to genetic and environmental factors • In whites, it is strongly associated to with HLA-DR3 or DR2 and DQB1

Systemic Lupus Erythematosus • Clinical Signs: • The first signs to appear are usually nonspecific such as fatigue, weight loss, malaise, fever, and anorexia • Joint involvement of small joints of the hands, wrist and knees is reported in over 90% of cases • A skin manifestation of an erythematous rash may appear in the area of body exposed to UV light • A classic butterfly rash across the nose and cheeks which is responsible for the name lupus may appear • Some patients may also exhibit renal involvement

Systemic Lupus Erythematosus • Renal involvement is usually in the form of lesions the most dangerous of which is glomerulonephritis • Immune complexes may deposit in the subendothelial tissue and thickening of the basement membrane results • All of these can result in renal failure and death • There might also be cardiac involvement with pericarditis, tachycardia, or ventricular enlargement. • CNS manifestation such as seizures, psychoses, or depression • Hematologic abnormalities such as anemia, leukopenia or lymphopenia are exhibited

Systemic Lupus Erythematosus • Immunological Findings: • The LE cell was discovered by Malcolm and Hargraves in 1948. • The LE cell is a neutrophil that has engulfed the antibody-coated nucleus of another neutrophil • The first anti-DNA antibody was discovered 9 years later • SLE is associated with more than 28 autoantibodies • Lupus patients appear to have overactive B cells especially the subset with the CD5 marker which increase in number

Systemic Lupus Erythematosus • The increased prevalence of the disease in women may be traced to the fact that estrogen enhance B cell activity • Estrogen also suppresses regulator activities of T cells as a result, there is a decrease in the absolute number of T cells • Complement is activated which results in decrease in the serum level of complement components • At the same time there is an increase in the level of breakdown products of complements such as C3d and C3a • IgG is most pathogenic and it forms complexes that are deposited in the glomerular basement membrane

Systemic Lupus Erythematosus • Accumulation of immune complex with complement activation is responsible for the damage to the kidney • Drug induced lupus differs from the chronic form of the disease: when the drug is withdrawn symptoms disappear • It is a milder form of the disease and manifest as arthritis or rashes • Drugs that have been implicated include procainamide hydrochloride, hydralazine hydrochloride, methyldopa etc.

Systemic Lupus Erythematosus • Laboratory Diagnosis of SLE: • A screening test for antinuclear antibody (ANA) is usually the first test done • Fluorescent antinuclear antibody (FANA) testing is most widely used • The test is sensitive but the specificity is low because many of the Abs are associated with other diseases • The test is an indirect IFA test which employs antihuman globulin tagged with a fluorescent marker. • About 5% of healthy individuals and b/w 10 and 30% of elderly individuals test positive

Systemic Lupus Erythematosus • If FANA is positive, then a profile testing should be done for individual Abs • More than 99% of patients with SLE will have a positive result for one or more tests

Systemic Lupus Erythematosus • Double-stranded DNA (ds-DNA): • These Abs are the most specific for SLE and are seen only in patients with SLE • Found in only 50 to 80% of cases but when seen, they are diagnostic of the disease • Abs to ds-DNA produce a peripheral staining pattern in IFA • A sensitive assay for ds-DNA utilizes Crithidia luciliae, a hemoflagellate as the substrate • A positive test is indicated by a brightly stained kinetoplast with a dilution of 1:10 or greater of patient serum

Systemic Lupus Erythematosus • Antihistone antibody: • Histone is a major component of chromatin • This antibody is found in lupus patients • It binds to DNA and may be found in all cases of drug induced lupus • If no other Abs are present, this may support a diagnosis of drug induced lupus • The Abs may be detected by IFA, RIA or EIA

Systemic Lupus Erythematosus • Antibodies are also produced against DNA complexed to histone known as deoxyribonucleoprotein (DNP) • The antibody is thought to be identical to the LE factor or phenomenon • It appears in 70 to 90% of patients with SLE • A slide method using latex particle coated with DNP have been used in a simple slide agglutination test for SLE • Anti-Sm antibody: • Antibody to extractable nuclear antigen was first described in a patient named Smith hence it is called anti-Sm

Systemic Lupus Erythematosus • Extractable nuclear Ags are small nuclear riboproteins that are associated with uridine-rich ribonucleic acid (RNA) • The Ab is specific for SLE and not found in other autoimmune diseases • Anti-Sm can be measured by double diffusion, passive hemagglutination, and EIA • SS-A/Ro and SS-B/La are also members of the family of extractable nuclear antigens. • Antibody to SS-A/Ro appears in 25 to 40% of patients with SLE

Systemic Lupus Erythematosus • It is found in patients with cutaneous manifestations of SLE • SS-B/La is found in 10 to 15% of patients with SLE and all of them have anti-SS-A/Ro • Antibodies are detected by the IFA test with the use of human tissue culture cells e.g. (Hep-2) human epidermal • Anti-nRNP: • Anti-nRNP produces a finely speckled IFA pattern • RNP is a nuclear RNA which is found in association with seven to eight nonhistone proteins

Systemic Lupus Erythematosus • The antibody is also found in high titer in individuals with mixed connective tissue disease and other autoimmune diseases • The antibody can be measured by double diffusion, passive hemaglutination and EIA and IFA • Treatment: • If the primary symptom is fever or arthritis a high dose of aspirin or other anti-inflammatory drug may bring relief • May also use antimalarials and topical steroids. Other drugs include cyclophosphamide, methotrexate etc.

Rheumatoid Arthritis • Rheumatoid arthritis is a systemic autoimmune disorder • It involves the synovial membrane of multiple joints • Women are more likely to be affected than men and usually strikes between the ages of 20 and 40 • Spontaneous remission may be experienced by some patients otherwise the disease may progress and result in deformity and disability • RA has been associated with certain of the HLA class II molecules. • HLA-DR1 and DR4 occur in 70% of patients with RA

Rheumatoid Arthritis • Clinical Signs: • Diagnosis of RA is based on the 1987 criteria established by the American College of Rheumatology • Symptoms include morning stiffness around the joints lasting at least 1 hour, swelling of the soft tissue around three or more joints • Others include swelling of the proximal interphalangeal, metacarpophalangeal, or wrist joints, symetric arthritis, subcutaneous nodules, a positive RF test • Also included is a radiographic evidence of erosion of the joints of the hands, the wrist, or both

Rheumatoid Arthritis • Usually begins with nonspecific symptoms such as fever, malaise, weight loss, and transient joint pain • Stiffness and joint pain that gradually improves during the day are characteristics exhibited by most patients • Joint are involved progressively to larger joints in a symmetric manner from the knees, hips, elbows, shoulders and cervical spine • About 25% of patients have nodules over the bones • Nodules may also be found in the myocardium, pericardium, heart valve, pleural, lungs, spleen, and larynx

Rheumatoid Arthritis • Immunologic Findings: • The main immunologic finding is the presence of RF • RF is a 19S Ab directed against the Fc portion of IgG • The Ab is not specific for RA as it is found in other diseases such as SLE, scleroderma, Sjögren’s syndrome and B cell lymphoproliferative disorders • It has been suggested that RF may be anti-idiotypic antibodies involved in the regulation of immune response • In RA, polyclonal activation of B cells may occur resulting in overwhelming amount of antibody to IgG

Rheumatoid Arthritis • Other autoAbs associated with RA include ANA, anticollagen Abs, Abs against cytoskeleton filamentous proteins etc. • These Abs may cause immune complex formation with the activation of complement which contribute to pathogenesis • Joint damage is due to invasion of inflammatory cells such as neutrophils, and macrophages • Proliferation of fibroblast, macrophages, mast cells, and stellar cells result in the formation of a pannus, an organized mass of cells that grow into the joint space

Rheumatoid Arthritis • Laboratory Diagnosis of Rheumatoid Arthritis: • Diagnosis is based on a combination of clinical manifestations, radiographic findings and lab tests • Laboratory screening test for RF using sheep red cells or latex particles are available and simple to perform • Quantitative test are also available which involve nephelometry and ELISA techniques • RF is found in other diseases such as syphilis, viral infections, leprosy, chronic liver disease, neoplasm and other inflammatory processes

Rheumatoid Arthritis • The RF test is thus not a specific test for RA and about 10% of patient with the disease test negative for RF • C-reactive protein and ESR are usually elevated and complements are normal or elevated • Treatment: • Treatment include palliatives with rest and nonsteroidal anti-inflammatory drugs like salicylates and ibuprofen • Slow-acting antirheumatic drugs (SAARDS) may also be used to treat the condition • New therapy include the use of monoclonal Abs that target T cells

Hashimoto’s Thyroiditis • Hashimoto’s thyroiditis and Graves’ disease are organ specific autoimmune diseases • Both diseases interfere with the thyroid gland function • The thyroid gland located in the anterior region of the neck consist of units called follicles • Follicles are lined with cuboidal epithelial cells and filled with colloid • The primary constituent of colloid is thyroglobulin which is made up of triiodothyronine (T3) thyroxine (T4) • TRH acts on the pituitary gland to induce the release of TSH

Hashimoto’s Thyroiditis • TSH binds to receptors on the cell membrane of the thyroid gland causing break down of thyroglobulin into T3 and T4 • AutoAbs may interfere with this process and cause under or overactivity of the thyroid • Hashimoto’s thyroditis is most often seen in women between the ages of 30 and 40 years • Patients develop a combination of goiter or enlarged thyroid, hypothyroidism and thyroid autoantibodies • An association with HLA antigens DR4 and DR5 has been noted. DQA1 and DQB1 genes seem to confer resistance

Hashimoto’s Thyroiditis • Immunologic Findings: • Lymphocytic infiltration is seen with development of germinal centers that almost replace the normal glandular architecture of the thyroid • Cell infiltrates include T and B cells, macrophages and plasma cells • Both CD4 and CD8 cells are found thus the disease is characterized by a cellular and a humoral response • Autoantibodies are found in up to 80% of cases

Hashimoto’s Thyroiditis • Laboratory Testing: • The autoantibodies present include Abs to thyroglobulin and to thyroid microsomal antigen now known as thyroid peroxidase • Some peroxidase Abs inhibit enzyme activity while others may mediate the cytotoxicity due to natural killer cells • Abs to thyroglobulin help to produce hypothyroid conditions • Other Abs include colloid Ab (CA2) thyrotropin-binding inhibitory immunoglobulin (TBII)

Hashimoto’s Thyroiditis • Others are thyroid stimulating immunoglobulin (TSI) and thyroid growth-stimulating immunoglobulin (TGSI) • Peroxidase Abs can be measured by particle agglutination assays, complement fixation, RIA and Indirect IFA • Abs to thyroglobulin can be measured by precipitaion in agar, indirect IFA, passive agglutination, RIA, and EIA • Indirect IFA use human or monkey thyroid tissue fixed to a slide • Antithyroglobulin Abs are found in about 80% of patients with the disease

Graves’ Disease • Graves’ disease is another autoimmune disease that affects the thyroid gland • Graves’ disease produces hyperthyroidism • It the most common cause of hyperthyroidism and affects about 0.5% of the population • Women are more susceptible than men by a margin of 7:1 and usually present between the ages of 30 and 40. • In whites, the disease is associated with the HLA antigen DR3 while in Asians HLA Bw35 and Bw36 occur more frequently

Graves’ Disease • HLA DQB1 appears to confer resistance to the disease • Clinical Signs: • Disease is presented as thyrotoxicosis with a diffusely enlarged goiter that is soft instead of rubbery • Signs include nervousness, insomnia, depression, weight loss, heat intolerance, sweating, rapid heart beat • Other signs include fatigue, cardiac dysrhythmias, restlessness, and exopthalmus

Graves’ Disease • Immunologic Findings: • The thyroid presents with Hyperplasia with a patchy infiltration of lymphocytes • Both CD4 and CD8 cells are present and the T cells appear to play a central role in the pathogenesis of the disease • The most significant Ab present is thyroid stimulating hormone receptor antibody (TRab) • Ag-Ab combination result in the stimulation of the receptor resulting in the release of the thyroid hormones • Another group of Abs called thyroid stimulating antibodies or immunoglobulins (TSab or TSI) may have different specificity

Graves’ Disease • Laboratory Diagnosis: • A key finding in Graves’ disease is elevated levels of total and free T3 and T4 • In addition, TSH levels are low due to Ab stimulation of the thyroid • Measurement of the thyroid Abs may be undertaken if the above assays are unclear • Treatment: • Antithyroid medication may be employed. Radioiodine which emits beta particles may be used. Surgery is also an option.

Insulin-Dependent Diabetes • This disease is characterized by insufficient production of insulin due to an autoimmune destruction of the beta cells of the pancreas • Peak onset is b/w 10 and 14 years of age • Disease may be attributed to genetic and environmental conditions • About 95% of white diabetics carry the HLA-DR3 or DR4 genes • It appears that true susceptibility genes for IDDM may occur in the HLA-DQ region

Insulin-Dependent Diabetes • Viral infections have been linked with diabetes • Mumps virus, rubella virus, CMV, and Coxsakie B4 virus have all been inconclusively linked to diabetes • Congenital rubella infection is the only one for which a link has been definitively identified • There appears to be similarity between coxsakie viral protein P2-C and the enzyme glutamic acid decarboxylase. • Antibodies are formed against glutamic acid decarboxylase in IDDM • Molecular mimicry could initiate Ab production against self Ag

Insulin-Dependent Diabetes • Immunopathology: • Inflammation of the islets of Langerhans in the pancreas leads to fibrosis and destruction of most of the beta cells • CD4 and CD8 B cells and macrophages are all involved in the destructive process of the islet cells • Cellular and humoral immunity are involved in this process • The subset of T cells that is activated determines whether the response is cellular or humoral

Insulin-Dependent Diabetes • Laboratory Testing: • IDDM is usually diagnosed by the presence of hyperglycemia • Abs to islet cells may be screened for by indirect IFA with human or rat islet cells • Islet cell may be detected in the sera of newly diagnosed diabetic cases • Abs to insulin may be detected by ELISA or RIA methods

Insulin-Dependent Diabetes • Treatment: • Insulin has been the standard form of treatment • New treatment methods center around the use of immunosuppressive agents • Agents that have been tried include azathioprine, cyclosporine A and prednisone • All these agents have potentially toxic effects

Multiple Sclerosis • Destruction of the myelin sheath results in the formation of lesions known as plaques in the white matter of the brain and spinal cord • Genetic and environmental factors predispose one to this disease • MS is associated with the inheritance of HLA antigen DRw15 and DRw6 • An inflammatory response to bacteria or virus may trigger the autoimmune process • Disease is most often seen in those b/w the ages of 20 & 50 and is more common in women

Multiple Sclerosis • 90% of patients alternate between remissions and relapses for many years • Within the plaques, CD4 cells, plasma cells and macrophages are found along with immunoglobulin • Immunoglobulin is increased in the spinal fluid in 60 to 80% of patients • They usually produce oligoclonal bands on protein electrophoresis • RIA is used to detect the Abs • Therapy include use of corticosteroids

Myasthenia Gravis • Symptoms of disease include facial weakness, difficulty in chewing, and swallowing, difficulty breathing • Others include inability to maintain support of the trunk, the neck or the head • Antibody mediated damage to the acetylcholine receptors in the skeletal muscle leads to muscle weakness • May be associated with the presence of other autoimmune diseases such as SLE • Appears to be linked with either HLA-B8 or DRw3 antigens

Myasthenia Gravis • 80 to 90% of patients have Abs to acetylcholine receptors which may be the main contributor to pathogenesis • Combination of the Abs to the receptors blocks the binding of acetylcholine which destroy the receptors • Abs can be detected with RIA methods • Anticholinesterase agents are employed in therapy

Goodpasture’s Syndrome • Goodpasture’s syndrome is a glomerulonephritis due to Abs reacting specifically with Ags in the kidney • Necrosis of the glomerulus is triggered by an Ab that reacts with glycoprotein present in the basement membrane of the glomerulus • Results in immune complex deposit and complement fixation which causes the damage to the kidney • This may eventually produce renal failure

Autoimmune Diseases