Immunology Pathophysiology

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jknell
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199452
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Immunology Pathophysiology
Updated:
2013-02-10 19:36:56
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Pathological immunology
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  1. Hypersensitivity disorders
    • Type I:
    • -Anaphylaxis
    • -Allergic and atopic disorders (e.g., rhinitis, hay fever, eczema, hives, asthma)
    • Presentation: immediate, anaphylactic, atopic

    • Type II:
    • -Hemolytic anemia
    • -Pernicious anemia
    • -Idiopathic thrombocytopenic purpura
    • -Erythroblastosis fetalis
    • -Acute hemolytic transfusion reactions
    • -Rheumatic fever
    • -Goodpasture's syndrome
    • -Bollous pemphigoid
    • -Pemphigus vulgaris
    • -Grave's disease
    • -Myasthenia gravis

    • Type III:
    • -SLE
    • -Rhematoid arthritis
    • -Polyarteritis nodosum
    • -Poststreptococcal glomerulonephritis
    • -Serum sickness
    • -Arthus reaction (e.g., swelling and inflammation following tetanus vaccine)
    • -Hypersensitivity pneumonitis (e.g., farmer's lung)
    • Can be associated with vasculitis and systemic manifestation

    • Type IV:
    • -Type 1 DM
    • -Multiple sclerosis
    • -Guillain-Barre syndrome
    • -Hashimoto's thyroiditis
    • -Graft-versus-host disease
    • -PPD (test for M. tuberculosis)
    • -Contact dermatitis (e.g., poison ivy, nickel allergy)
    • Response is delayed and does not involve antibodies
  2. Blood transfusion reactions
    • Allergic reactionType I hypersensitivity rxn against plasma proteins in transfused blood
    • Presentation: Urticaria, pruritius, wheezing, fever
    • Tx: antihistamines

    • Anaphylactic reaction: Severe reaction. IgA-deficient individuals must receive blood products that lack IgA
    • Presentation: Dyspnea, bronchospasm, hypotension, respiratory arrest, shock

    • Febrile nonhemolytic transfusion reaction (FNHTR): Type II hypersensitivity reaction. 
    • -Host Ab against donor HLA antigens and leukocytes
    • Presentation: fever, ehadaches, chills, flushing

    • Acute hemolytic transfusion reaction (HTR): Type II hypersensitivity reaction
    • -Intravascular hemolysis (ABO blood group incompatibility)
    • -extravascular hemolysis (host Ab reaction against foreign antigen on donor RBCs)
    • Presentation: Fever, hypotension, tachypnea, tachycardia, flank pain, hemoglobinemia (intravascular), jaundice (extravascular hemolysis)
  3. Autoantibodies
    • Antibody         -        Associated disorder
    • Antinuclear antibodies (ANA)        SLE, nonspecific
    • Anti-dsDNA, anti-Smith        SLE
    • Antihistone        Drug-induced lupus
    • Anti-IgG (rheumatoid factor)        Rhematoid arthritis
    • Anticentromere        Scleroderma (CREST)
    • Anti-Scl-70 (anti-DNA topoisomerase I)       Scleroderma (diffuse)
    • Antimitochondrial        Primary biliary cirrhosis
    • Antigliadin, antiendomysial        Celiac
    • Anti-basement membrane        Goodpasture's syndrome
    • Anti-desmoglein        Pemphigus vulgaris
    • Antimicrosomal, antithyroglobulin        Hashimoto's thyroiditis
    • Anti-Jo-1        Polymyositis, dermatomyositis
    • Anti-SS-A (anti-Ro)        Sjogren's syndrome
    • Anti-SS-B (anti-La)        Sjogren's syndrome
    • Anti-Ul RNP (ribonucleoprotein)        Mixed connective tissue disease
    • Anti-smooth muscle        Autoimmune hepatitis
    • Anti-glutamate  decarboxylase        Type 1 diabetes mellitus
    • c-ANCA        Wegener's granulomatosis
    • p-ANCA        Other vasculitides
  4. Infections in immunodeficiency
    • No T cells:
    • -Bacteria → sepsis
    • -Virus → CMV, EBV, VZV, chronic infection with respiratory/GI viruses
    • -Fungus/parasites → candida, PCP


    • No B cells:
    • -Bacteria → Encapsulated: Streptococcus, Staphylococcus, Haemophilus, Moraxella
    • -Virus → Enteroviral encephalitis, poliovirus (live vaccine contraindicated)
    • -Fungi/parasites →GI giardiasis (no IgA)

    • No granulocytes:
    • -Bacteri → Staphylococcus, Pseudomonas
    • -Fungi/parasites → Candida, Nocardia, Aspergillus

    • No complement:
    • -Bacteria → Neisseria (no Mycobacterium avium complex)

    • *B cell deficiencies→recurrent bacterial infections
    • *T cell deficiencies → fungal and viral infections
  5. Immune deficiencies
    B-cell disorders
    • Bruton's agammaglobulinemia
    • Hyper-IgM syndrome
    • Selective Ig deficiency
    • Common variable immunodeficiency (CVID)
  6. Bruton's agammaglobulinemia
    X-linked recessive (↑ in Boys). Defect in BTK, a tyrosine kinase gene → blocks pro-B cells from forming pre-B cells

    • Presentation: Recurrent bacterial infection after 6 months
    • (↓ maternal IgG) due to opsonization defect.
    • -Absence of thymic shadow

    Labs: normal pro-B, ↓ maturation, ↓ number of B cells, ↓ immunoglobulins of all classes
  7. Hyper-IgM syndrome
    Defective CD40L on helper T cells = inability to class switch

    Presentation: severe pyogenic infections early in life

    • Labs:
    • ↑IgM, ↓↓ IgG, IgA, IgE
  8. Selective Ig deficiency
    Defect in isotype switching → deficiency in specific class of immunoglobulins

    • Presentation: sinus and lung infections, milk allergies and diarrhea,
    • -Anaphylaxis on exposure to blood products with IgA

    • Labs:
    • IgA deficiency most common (failure to mature into plasma cells)
    • -↓ secretory IgA
  9. Common variable immunodeficiency
    (CVID)
    Defect in B cell maturation; many causes

    Presentation: Can be acquired in 20s-30s; ↑ risk of autoimmune disease, lymphoma, sinopulmonary infections

    • Labs:
    • Normal number of B cells; ↓ plasma cells, immunoglobulin
  10. Immune deficiencies
    T-cell disorders
    • Thymic aplasia (DiGeorge syndrome)
    • IL-12 receptor deficiency
    • Hyper-IgE syndrome (Job's syndrome)
    • Chronic mucocutaneous candidiasis
  11. Thymic aplasia
    DiGeorge syndrome
    22q11 deletion; failure to develop 3rd and 4th pharyngeal pouches

    • Presentation
    • -Tetany (hypocalcemia)
    • -recurrent viral/fungal infections (T-cell deficiency)
    • -Congenital heart and great vessel defects

    • Labs:
    • THymus and parathyroids fail to develop →↓ T cells, ↓ PTH, ↓ Ca2+
    • -Absent thymic shadow on CXR
  12. IL-12 receptor deficiency
    ↓ Th1 response

    Presentation: Disseminated mycobacterial infection

    Labs: ↓ IFN-γ
  13. Hyper-IgE syndrome
    Job's syndrome
    Th cells fail to produce IFN-γ→ inability of neutrophils to respond to chemotactic stimuli

    • PresentationFATED
    • -coarse Facies
    • -cold (noninglamed) staphylococcal Abscesses
    • -retained primary Teeth
    • -increased IgE
    • -Dermatologic problems (eczema)

    Labs: increased IgE
  14. Chronic mucocutaneous candidiasis
    T-cell dysfunction

    PresentationCandida albicans infections of skin and mucous membrane
  15. Immune deficiencies
    B- and T-cell disorders
    • Severe combined immunodeficiency (SCID)
    • Ataxia-telangiectasia
    • Wiskott-Aldrich syndrome
  16. Severe combined immunodeficiency
    SCID
    • Several types:
    • -Defective IL-2 receptor (most common, X-linked)
    • -adenosine deaminase deficiency
    • -failure to synthesize MHC II antigens

    • Presentation:
    • -Recurrent viral, bacterial, fungal, protozoal infection due to both B- and T-cell deficiency
    • -Absent thymic shadow
    • -Absent germinal centers (lymph node biopsy)
    • -Absent B cells (peripheral blood smear)

    Tx:  bone marrow tranplant (no allograft rejection)

    • Labs:
    • - ↓ IL-2R = ↓ T-cell activation
    • - ↑ adenine = toxic to B and T cells
    • - (↓ dNTPs, ↓ DNA synthesis.)
  17. Ataxia-telangiectasia
    Defects in the ATM gene, which codes for DNA repair enzymes

    • Presentation: triad
    • -Cerebellar defects (ataxia)
    • -Spinder angiomas (telangiectasia)
    • -IgA deficiency

    LabsIgA deficiency
  18. Wiskott-Aldrich syndrome
    X-linked recessive defect; progressive deletion of B and T cells

    • Presentation: triad (TIE)
    • -Thrombocytopenic purpura
    • -Infections
    • -Eczema

    Labs: ↑ IgE, IgA; ↓IgM
  19. Immune deficiencies
    Phagocyte dysfunction
    • Leukocyte adhesion deficiency (type 1)
    • Chediak-Higashi syndrome
    • Chronic granulomatous disease
  20. Leukocyte adhesion deficiency (type 1)
    Defect in LFA-1 integrin (CD1) protein on phagocytes

    • Presentation: 
    • -Recurrent bacterial infections
    • -absent pus formation
    • -delayed separation of umbilicus

    Labs: neutrophilia
  21. Chediak-Higashi syndrome
    • Autosomal recessive; defect in lysosomal regulating trfficking gene (LYST)
    • -Microtubule dysfunction in phagosome-lysosome fusion

    • Presentation:
    • -Recurrent pyogenic infections by staph and strep
    • -partial albinism
    • -peripheral neuropathy
  22. Chronic granulomatous disease
    • Lack of NADPH
    • -oxidase → ↓ reactive oxygen species (e.g. superoxide) and absent repiratory burst in neutrophils

    • Presentation:
    • -↑ susceptibility to catalase positive organisms (e.g. S. aureus, E. coli, Aspergillus)

    Labs: Negative Nitroblue tetrazolium dye reduction test
  23. Grafts
    • Autograft - from self
    • Syngeneic graft - from identical twin or clone
    • Allograft - from non-identical individual of same species
    • Xenograft - from different species
  24. Transplant rejections
    types, time frame
    • Hyperacute, within minutes
    • Acute, weeks later
    • Chronic, months to years
    • Graft-versus-host, varies
  25. Hyperacute rejection
    Antibody mediated (type II) due to rpesence of preformed anti-donor antibodies in the recipient

    Presentation: occludes graft vessels, causing ischemia and necrosis
  26. Acute rejection
    • Cell-mediated due to CTLs reacting against foreign MHCs
    • -Reversible with immunosuppressants (e.g., cyclosporine, OKT3)

    Presentation: Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate
  27. Chronic rejection
    Class I-MHCnon-self is perceived by CTLs as class I-MHCself presenting a non-self antigen

    • Presentation: Irreversible
    • -T-cell and antibody-mediated vascular damage (obliterative vascular fibrosis
    • -fibrosis of graft tissue and blood vessels
  28. Graft-versus-host disease
    • Graft immunocompetent T cells proliferate in the irradiated, immunocompromised disease host
    • ...reject cells with "foreign" proteins, resulting in severe organ dysfunction

    • Presentation:
    • -Maculopapular rash
    • -Jaundice
    • -HSM
    • -diarrhea
    • -usually in bone marrow and liver transplant (lymphocyte rich organs)
    • -Potentially beneficial in bone marrow transplant
  29. Immunosuppressants
    Rx
    • Cyclosporine
    • Tacrolimus (FK506)
    • Sirolimus (rapamycin)
    • Daclizumab
    • Azathioprine
    • Muromonab-CD3 (OKT3)

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