Immune Disorders: HLA and Disease Associations and Amyloidosis Nancy L. Jones, M.D.

Human Luekocyte Antigen Complex Significance of HLA complex or MHC as a regulator of immune response Bind peptide of foreign proteins for presentation to appropriate T cells know as MHC restriction Chromosomes 6 and chromosome 15 for the β2-microglobulin Highly polymorphic and presents a barrier to transplantation of organs

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HLA Class I antigens HLA-A , HLA-B, HLA-C each a heterodimer Heavy α chain (44-kD) and smaller (12-kD)β2 micro globulin noncovalently associated with each other Found on virtually all nucleated cells and platelets Extracellular portion of α chain contains a cleft where foreign peptides bind to MHC molecules Present foreign peptides to CD8+T cells (viral antigens processed within cell) Cytotoxic T cell lysis of virus infected cells

Figure 6-9 The HLA complex and the structure of HLA molecules Figure 6-9 The HLA complex and the structure of HLA molecules. A, The location of genes in the HLA complex is shown. The sizes and distances between genes are not to scale. B, Schematic diagrams and crystal structures of class I and class II HLA molecules. (Crystal structures are courtesy of Dr. P. Bjorkman, California Institute of Technology, Pasadena, CA.) Downloaded from: Robbins & Cotran Pathologic Basis of Disease (on 17 February 2005 01:49 PM) © 2005 Elsevier

HLA Class II antigens HLA-D with sub regions DP, DQ, and DR, each a heterodimer Comprised of α and β subunits Found on antigen presenting cells, macrophages and B cells May be induced on endothelial cells, renal tubular epithelial cells and fibroblasts by IFN-α Present foreign peptides to CD4+ T cells (bacterial proteins synthesized outside cell) via the cleft in the extracellular portion Cytokine mediated protective response

HLA Class III components of complement C2, C3 and Bf Cytokines, TNF and lymphotoxin TNF-β also encoded at same site DO NOT act as histocompatibility antigens TNF is tumor necrosis factor

HLA Six different class I HLA molecules expressed, three maternal and three paternal (over 400 HLA-B alleles have been identified) Can have over 20 different MHC II molecules Amino acid sequence of peptide determines which MHC allele will bind a given peptide

HLA Transplant rejection is the result of mismatched HLA haplotype, the combination of HLA alleles in each individual Evokes humoral and cell mediated responses leading to graft destruction

HLA Genetic regulation of immune response MHC has a role in T-cell stimulation Can only bind and present antigen if the proper MHC molecules have been inherited Type of immune response inherited and nature of antigen determine disposition to hypersensitivity reactions

HLA Many diseases are associate with particular HLA alleles Inflammatory disease Autoimmune diseases Mechanisms of association are not understood at present

HLA Disease Associations Allele Disease Relative Risk HLA-B27 Ankylosing Spondylitis 90-100% HLA-B27 Postgonococcal arthritis 14 HLA-B27 Acute anterior uveitis 15 HLA-DR4 Rheumatoid arthritis 4 HLA-DR3 Autoimmune hepatitis 14 HLA-DR3 Primary Sjogren syndrome 10 HLA-DR3 Type 1 diabetes mellitus 5 HLA-DR4 “ 6 HLA-DR3/DR4 “ 15 Bw47 21-hydroxylase deficiency 15

Amyloidosis A disorder characterized by extracellular deposition of mis-folded proteins that aggregate into insoluble fibrils These deposition of these proteins may be due to excessive production of proteins prone to mis-folding and aggregation; mutations that produce proteins that cannot fold properly and tend to aggregate; or defective or incomplete proteolytic degradation of extracellular proteins

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Amyloidosis May be localized or systemic Found in association with a variety of primary disorders including monoclonal B-cell proliferations where the amyloid deposits consist of immunoglobulin light chains; chronic inflammatory disorders such as rheumatoid arthritis with deposits of amyloid A protein derived from an acute-phase protein produced in inflammation

Amyloidosis May be found in Alzheimer disease with deposition of amyloid β protein; in familial conditins in which the amyloid deposits consist of mutations of normal proteins such as transthyretin in familial amyloid polyneuropathies Amyloidosis is associated with dialysis with deposits of β2-microglobulin, whose clearance is defective.

Amyloidosis Amyloid deposits cause tissue injury and impair normal function by causing pressure on cells and tissues, but there is no inflammatory response to the deposits.

Amyloidosis All amyloid has same morphology but is made up of many different proteins (up to 23 identified so far) Deposits composed of nonbranching fibrils, 7.5 to 10 nm in diameter, formed of β-sheet polypeptide chains wound together. Congo red binds to fibrils and produces a red-green birefringence.

Structure of amyloid fiber

Electron micrograph of amyloid fibrils

Histology of Amyloidosis The deposition is always extracellular and begins between cells Surrounds and destroys cells over time Perivascular and vascular localizations are common in immunocyte-associated forms Diagnosis based on staining characteristics Congo red gives a pink or red color under ordinary light with polarization the amyloid shows apple-green birefringence

H&E stain of renal amyloid

Renal Amyloid congo red stain

Polarized congo red stain of renal amyloid

Gross Amyloid in the Kidney

Amyloid in spleen

Gross Amyloid in Spleen

Amyloid in the liver

Gross Amyloid in Liver

Cardiac Amyloidosis

Gross Amyloid in Heart

Amyloidosis Amyloid light chain protein (AL) produced by plasma cells Complete Ig light chains, the amino-terminal fragment or both (monoclonal B-cell proliferations) Amyloid associated fibril (AA) Nonimmunoglobulin protein derived from 12-kD serum amyloid associated protein (SAA) made in the liver in chronic inflammatory states or in enzymatic defects Aβ amyloid a 4-kD peptide found in cerebral lesions of Alzheimer disease derived from amyloid precursor protein and larger gylcoprotein

Amyloidosis Transthyretin (TTR) a normal serum protein that binds and transports thyroxine and retinol mutations lead to familial amyloid polyneuropathies. Found in hearts of the elderly (senile systemic amyloidosis) Some familial amyloidosis is associated with deposits of mutant lysozyme

Amyloidosis β2-microglobulin has been found as the amyloid fibril subunit (Aβ2m) in patients on long term dialysis 60-80% of patients on long term dialysis have deposits in synovium, joints and tendon sheaths Procalcitonin and keratin have also been reported in amyloid deposits

Classification of Amyloidosis Immunocyte Dyscrasias with Amyloidosis (Primary Amyloidosis) Systemic AL type Most common form ~ 3000 cases/yr in US Associated with multiple myeloma γ or κ light chains (Bence Jones proteins) Patients with other underlying B-cell dyscrasias with increased plasma cells and immunoglobinopathy

Classification of Amyloidosis Reactive Systemic Amyloidosis Was previously called secondary amyloidosis Systemic in distribution and composed of AA protein Associated with chronic inflammatory states Tuberculosis, bronchiectasis and chronic osteomyelitis RA, ankylosing spondylitis and inflammatory bowel disease (autoimmune disorders) “skin popping” with chronic infections Renal cell carcinoma and Hodgkin lymphoma

Classification of Amyloidosis Familial (Hereditary) Amyloidosis are rare and in limited geographic areas Autosomal recessive familial Mediterranean fever Armenians, Sephardic Jews and Arabs Inflammation of serosal surfaces and synovial membrane Gene produces pyrin which regulates acute inflammation Autosomal dominant familial disorders with deposition of amyloid in peripheral and autonomic nerves known as amyloidotic polyneuropathies Found in Portugal, Japan, Sweden, and the US Fibrils are composed of mutant ATTRs.

Classification of Amyloidosis Localized Amyloidosis Single organ or tissue Nodular masses which may be seen grossly Lung, larynx, skin, urinary bladder, tongue and the region of the eye Lymphocytes and plasma cells surround amyloid deposits are they the cause or a reaction? One form involves AL protein Microscopic lesions only

Classification of Amyloidosis Endocrine Amyloid Microscopic deposits found in endocrine tumors such as medullary carcinoma of the thyroid gland (derived from polypeptide hormones), islet tumors (islet amyloid polypeptide), pheochromocytomas and undifferentiated tumors of the stomach Also found in Islets of Langerhans in type 2 diabetes

Classification of Amyloidosis Amyloid of Aging Senile systemic amyloidosis is a systemic deposition of amyloid in patients in their 70s or 80s Dominant involvement and dysfunction of the heart presenting as a restrictive cardiomyopathy and arrhythmias Amyloid is composed of normal TTR molecules One form involves only the heart and is composed of a mutant TTR 4% of black population in US carry mutant allele and cardiomyopathy found in homozygous and heterozygous form

Amyloidosis Primary amyloidosis can lead to conditions that include: Carpal tunnel syndrome dialysis patients Cardiomyopathy leading to congestive heart failure Intestinal malabsorption Liver enlargement Kidney failure and nephrotic syndrome Neuropathy Orthostatic hypotension

Amyloidosis Symptoms include: Abnormal heart rhythm Enlarged tongue Fatigue Numbness of hands and feet Shortness of breath Skin changes Swallowing problems Swelling in the arms and legs Weak hand grip Weight loss

Other symptoms include: Decreased urine output Diarrhea Hoarseness or changes in the voice Joint pain weakness

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