Immunology Clinical Correlate Rheumatologic Diseases

Immunology Clinical Correlate Rheumatologic Diseases November 6th, 2007 Tejal Thakkar, MD Immune system  There are two main categories of host defense. Natural or Innate immunity vs Acquired or Adaptive immunity Innate Skin, mucous membranes Complement, CRP Macrophages, neutrophils, NK Monokines (IL-1, TNF, IL-12, interferons Adaptive Mucosal immune systems Antibody Lymphocytes Lymphokines (interleukins) Physical Barriers Circulating Factors Cells Cell-derived mediators Innate immunity     Innate immunity is your first line of defense against a pathogen It is activated immediately and coordinates with the adaptive immune system Innate immunity activates cytokines (including IL-1, TNFα, IL-8) that in turn recruit neutrophils and leukocytes. It can also stimulate NK cells and TH1 cell mediated immune responses. Innate immunity interacts with adaptive immunity by allowing the formation of MHC class II molecules which can then be presented to T-cells to stimulate an adaptive immune response Adaptive Immunity   Adaptive immunity can be both active and passive Active immunity is when the host plays an active role in responding to an antigen  ie immunizations cause hosts to respond to foreign antigens by producing antibodies and lymphocyte based memories   Passive immunity involves the transfer of soluble factors from an immune host to a non-immune host The adaptive immune system consists of T and B cells The T Cell       Derived from the thymus The T cell is the principal regulator of the immune response. The majority of circulating lymphocytes in the blood stream are T-cells Cellular immunity is mediated by T cells It distinguishes self from non-self by the use of specific antigen receptors and targets. T cell receptors are what bind to the MHC receptors on antigen presenting cells. Types of T cells T cells can be classified into helper/inducer, suppressor and cytotoxic subsets  Helper T cells can be divided into Th1 and Th2 helper T cells  Th1 secrete IL-2, TNF and interferon γ  Th2 secrete many of the IL’s (4,5,6,10,13) responsible for humoral immmunity  B-Cells Derived from the bone marrow  Express surface immunoglobulin on their surfaces  Humoral immunity is mediated by antibody produced by B cells and plasma cells  MHC  Major histocompatibility complex is a group of genes located on chromosome 6. -Class I molecules are expressed on the surface of nucleated cells -Class II molecules are found on antigen presenting cells -Class III molecules are proteins that cannot present antigen (C2, C4, TNF) Human leukocyte antigens (HLA) HLA can be used almost interchangeably with MHC  Composed of first 2 classes of MHC: Class I (HLA A, B & C) and Class II (HLADR, DP & DQ)  Rheumatologic HLA Associations HLA DR1: Rheumatoid Arthritis  HLA DR3: SLE, Sjogren’s Syndrome  HLA DR4: Rheumatoid Arthritis  HLA DR5: Juvenile Rheumatoid Arthritis, Hashimoto’s thyroiditis  HLA DQ: SLE  HLA B27: Seronegative spondylarthropathies  Do HLA cause autoimmune disease?     The role of HLA in autoimmune disease is variable Not everyone with a specific HLA will have the disease that may be associated with it. In some cases having a specific HLA makes a host more susceptible to developing an autoimmune disease In other cases HLA may be commonly inherited with another gene that confers susceptibility to a disease Tolerance Occurs when the immune system encounters certain antigens to which it is programmed specifically to not respond to.  Tolerance is present in both innate and adaptive immunity  Tolerance develops not only for antigens like the body’s own tissue but also for exogenous antigens, like dietary proteins.  Autoimmunity       Autoimmunity is the loss of a previously established tolerance. When autoimmunity occurs innate immunity or adaptive immunity or both have gone wrong! It is an immune response directed against an antigen within the body of the host. Can occur when the immune system is chronically stimulated It is not restricted to a T-cell or B-cell response. Autoimmunity only requires that the immune response be directed to a self-antigen. Antibody effects on immune/inflammatory responses Antibody can coat and neutralize invading organisms, preventing the organism access to the host  IgM and IgG activate complement resulting in chemotaxis, increased vascular permeability and target cell lysis  Antibody coats foreign particle thereby increasing the efficiency of phagocytosis.  Autoantibodies Autoantibodies are composed of both B cells and T cells.  Autoantibodies are known to increase transiently during immune activation.  This reaction is mediated by CD5 B cells  Normally autoantibodies also increase with age which may suggest a loss of tolerance as we age.  Autoantibodies Anti-nuclear antibodies (ANA) Systemic Lupus Erythematous Anti-dsDNA, anti Smith Anti-histone Anti-IgG (rheumatoid factor) Anti-neutrophil Anti-centromere Anti-Scl-70 Anti-microsomal Specific for SLE Drug induced lupus Rheumatoid Arthritis Vasculitis Scleroderma Scleroderma Hashimoto’s thyroiditis Rheumatoid Arthritis (RA)      Typically effects females > males 3:1 ratio Age: Women 40-60 years, men later Usually begins slowly with arthritic symptoms of pain, swelling, stiffness worsening over several months Most commonly affects MCP joints, wrist and PIP, but can affect any joint Joint involvement is symmetrical Etiology      Still largely unknown It is thought to be multifactorial with genetic factors (HLA DR4) and environmental factors. HLA DR4 does occur in 20-30% of the general populations RA is thought to initiated by T lymphocytes recognizing antigens in synovial tissue Activated T-cells and macrophages produce cytokines (TNF α and IL-1) that stimulate prostaglandins, adhesion molecules and proteinases that further lead to synovitis and tissue destruction. Rheumatoid Joint The synovium is the primary site for the inflammatory process. The infiltrate consists of mononuclear cells, helper T cells, macrophages and plasma cells. The synovial cells proliferate causing a pannus which can invade bone and cartilage RA Histopathology Bone Erosion Pannus Diagnosis of RA   Primarily a clinical diagnosis To be classified as RA a patient must have at least 4 of the following criteria. 1. 2. 3. 4. 5. 6. 7. Morning Stiffness in and around the joints lasting at least 1 hour before maximal improvement Soft-tissue swelling of 3 or more joint areas observed by a physician Swelling of the PIP, MCP or wrist joints for at least 6 weeks Symmetric arthritis Subcutaneous nodules Positive test for rheumatoid factor Radiographic erosions or periarticular osteopenia in hand or wrist joints Subcutaneous nodules Laboratory Findings in RA Anemia of chronic disease  Elevated platelets  Elevated ESR and CRP (acute phase reactants)  Positive rheumatoid factor  Positive ANA in 30%  Positive Anti CCP (cyclic citrullinated peptide)  C3, C4, CH50 are elevated  Rheumatoid Factor     Rheumatoid Factor (RF) are antibodies that recognize the Fc portion of an IgG molecule as their antigen The antibodies can be of any isotype, but are usually IgM Many conditions associated with chronic inflammation are associated with positive RFs 70% of RA patients are positive at onset of disease with another 10-15% of patients becoming positive in the first 2 years. Anti-Cyclic Citrullinated Peptide Anti-CCP is highly specific (98%) for RA  Found in 70% of patient with positive RF and in 33% of patients with negative RF  It is helpful as a diagnostic tool when it is difficult to differentiate RA from another arthritic condition.  Treatment    Current treatment strategies are aggressive and include early treatment with a DMARD (disease modifying anti-rheumatic drug) in conjunction with NSAIDs, low-dose prednisone, physical therapy and calcium supplementation to prevent osteoporosis Most common DMARDs include methotrexate and leflunomide (arava) New biologic response modifiers like etanercept (enbrel) and infliximab (remicade) Treatment: Steroids  Steroids have anti-inflammatory effects Decrease neutrophil margination, migration and accumulation  Inhibit neutrophil and macrophage phagocytosis, enzyme release and cytokine production  Decrease T-cell proliferation and IL-2 synthesis and secretion.  Treatment: DMARDs To be classified as a DMARD a drug must show sustained improvement in either physical function, decreased inflammatory synovitis or slowing/prevention of structural joint damage.  Examples of DMARDs include methotrexate, leflunomide, gold, hydroxychloroquine and sulfasalazine  DMARDs mechanism of action   Methotrexate in the low doses used for treatment in RA inhibits AICAR transformylase which stimulates the release of adenosineinhibits neutrophil function and has anti-inflammatory properties Leflunomide inhibits an enzyme leading to a decreased synthesis of uridine decreased synthesis of pyrimidines decreased synthesis of lymphocytes Treatment: Biologic Agents Monoclonal antibodies: Against T/B-cell surface molecules, cytokines, adhesion molecules, complement, costimulatory molecules  Biologics targeting T/B-cell collaboration molecules  Biologics targeting inflammatory cytokines  Etanercept  Derived from Chinese hamster ovary cells. It binds soluble TNFα and TNF β Remicade aka Infliximab  Derived from chimeric mouse-human monoclonal antibody. It binds both soluble and cell bound TNFα and therfore has the ability to kill cell with TNFα bound to its surface Systemic Lupus Erythematous Lupus, Latin for wolf, was used in the 18th century to describe a multitude of skin lesions  The first described case of SLE was in 1833  Systemic Lupus Erythematous    More common in African Americans and Hispanic patients Typically effects women between the ages of 15 and 45 years and is a nearly 8:1 female to male ratio. Predominance in women suggests linkage with sex hormones as the incidence decreases to 2:1 for post-menopausal women compared to men in the same age group. SLE: Genetic Associations High prevalence in monozygotic twins  C1q deficiency (96% have SLE)  HLA DR2 and DR3 associations  C2, C4 deficiencies (possibly inherited)  reduced TNFa  Diagnosis of SLE  Diagnosed in patients with 4 of the following 11 criteria serially or simultaneously. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Malar rash Discoid rash Photosensitivity Oral Ulcers Arthritis Serositis Renal disorder Neurologic disorder Hematologic disorder Immunologic disorder Antinuclear antibody (ANA) Malar Rash Discoid lupus An attenuated epidermis is surmounted by an orthohyperkeratotic scale with follicular plugging. Courtesy of Cynthia Magro, MD. Lupus Arthritis Laboratory Findings Anemia  Leukopenia  Thrombocytopenia  Elevated ESR and CRP  Decreased complements C3,C4 possibly due to consumption by immune complexes vs inherited deficiencies  Anti-nuclear antibody Identified by a indirect immunofluorescence test  A patient’s serum is diluted and layered onto a slide with pre-fixed tissue or cells  Then a tagged antibody reagent directed toward human immunoglobulin is added.  Any antibodies from the patient will be stained and will fluoresce when viewed under a fluorescence microscope  ANA patterns of fluorescence homogeneous speckled peripheral nucleolar Anti-nuclear antibody Not specific for the diagnosis of SLE  Some studies show that 32% of healthy individuals have a positive ANA  Peripheral or rim pattern is most specific for SLE  Speckled is the most commonly seen pattern and is seen in SLE as well as other diseases therefore is the least specific  Sensitivity of ANA in autoimmune and nonrheumatic disease Disease Sensitivity SLE Scleroderma Mixed Connective Tissue Disease Polymyositis/dermatomyositis Rheumatoid Arthritis Sjogren’s syndrome Hashimoto’s thyroiditis Grave’s Disease 95-100% 60-80% 100% 61% 52% 40-70% 46% 50% Other antibodies of interest Anti-ds-DNA  Anti-Sm  Anti-Ribosomal P proteins  Anti-Proliferating cell nuclear antigen  ** All of these have a high diagnostic specificity for SLE Anti-dsDNA and lupus nephritis   Anti-dsDNA is thought to have a causative factor in lupus nephritis Supportive evidence includes 1. 2. 3. 4. Anti-dsDNA are found in the glomeruli of apatients and animals with active disease Higher density of IgG anti-dsDNA in glomerular tissues vs other organs Longitudinal studies in lupus patients have found patients with higher titers more frequently have active nephritis In animal studies injection of monoclonal IgG antidsDNA can cause glomerular pathology Renal Immunofluorescense Kidney biopsy from a patient with diffuse proliferative lupus nephritis showing, on immunofluorescence microscopy, massive lumpy bumpy deposits of IgG. Treatment of SLE Depends on the physical manifestations  Includes: NSAIDs Steroids Antimalarials Imunosuppressive drugs  Treatment: Steroids Both topical and systemic steroids can be used to treat many of the physical manifestations of SLE  Lower doses are used to treat skin manifestations  However very high doses may be required for systemic manifestations like lupus nephritis.  Treatment: Antimalarials Most commonly used agent is Hydroxychloroquine (aka Plaquenil)  Antimalarials decrease antigen processing and presentation by both macrophages and lymphoid dendritic cells.  Ultimately this leads to decreased production of cytokines and TNF  Treatment: Immunosuppresive Used primarily for life threatening lupus manifestations.  Azathioprine (aka Imuran) is the most commonly used immunosuppresive drug.  Azathioprine is a purine analog of 6mercaptopurine. It suppresses DNA synthesis which causes cytotoxicity and decreased cellular proliferation  The End