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Immunology - Immune Responses Flashcards

1
Q

Acute-phase reactants

  • General
  • Positive (upregulated)
    • Serum amyloid A
    • C-reactive protein
    • Ferritin
    • Fibrinogen
    • Hepcidin
  • Negative (downregulated)
    • Albumin
    • Transferrin
A
  • General
    • Factors whose serum concentrations change significantly in response to inflammation
    • Produced by the liver in both acute and chronic inflammatory states.
    • Induced by IL-6, IL-1, TNF-α, and IFN-γ.
  • Positive (upregulated)
    • Serum amyloid A
      • Prolonged elevation can lead to amyloidosis.
    • C-reactive protein
      • Opsonin; fixes complement and facilitates phagocytosis.
      • Measured clinically as a sign of ongoing inflammation.
    • Ferritin
      • Binds and sequesters iron to inhibit microbial iron scavenging.
    • Fibrinogen
      • Coagulation factor
      • Promotes endothelial repair
      • Correlates with ESR
    • Hepcidin
      • Prevents release of iron bound by ferritin –>Ž anemia of chronic disease.
  • Negative (downregulated)
    • Albumin
      • Reduction conserves amino acids for positive reactants.
    • Transferrin
      • Internalized by macrophages to sequester iron.
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2
Q

Complement (204)

  • Overview
  • Activation
  • Functions
  • Opsonins
  • Inhibitors
A
  • Overview
    • System of interacting plasma proteins that play a role in innate immunity and inflammation.
    • MAC defends against gram-negative bacteria.
  • Activation
    • Classic** pathway—Ig_G_** or IgM mediated.
      • GM makes classic cars.
    • Alternative pathway—microbe surface molecules.
    • Lectin pathway—mannose or other sugars on microbe surface.
  • Functions
    • C3b—opsonization.
      • C3b** _b_inds bacteria.**
    • C3a**, C4**a**, C5**a**—**anaphylaxis.
    • C5a—neutrophil chemotaxis.
    • C5b-9—cytolysis by membrane attack complex (MAC).
  • Opsonins
    • C3b and IgG are the two 1° opsonins in bacterial defense
    • C3b also helps clear immune complexes.
  • Inhibitors
    • Decay-accelerating factor (DAF, aka CD55) and C1 esterase inhibitor help prevent complement activation on self cells (e.g., RBC).
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3
Q

Complement disorders

  • C1 esterase inhibitor deficiency
  • C3 deficiency
  • C5–C9 deficiencies
  • DAF (GPI anchored enzyme) deficiency
A
  • C1 esterase inhibitor deficiency
    • Causes hereditary angioedema.
    • ACE inhibitors are contraindicated.
  • C3 deficiency
    • Increases risk of severe, recurrent pyogenic sinus and respiratory tract infections
    • Increases susceptibility to type III hypersensitivity reactions.
  • C5–C9 deficiencies
    • Increase susceptibility to recurrent Neisseria bacteremia.
  • DAF (GPI anchored enzyme) deficiency
    • Causes complement-mediated lysis of RBCs and paroxysmal nocturnal hemoglobinuria.
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4
Q

Important cytokines:
L 1-6 (mnemonic)

A
  • “Hot T-bone stEAK”
  • IL-1: fever (hot).
  • IL-2: stimulates T cells.
  • IL-3: stimulates bone marrow.
  • IL-4: stimulates IgE production.
  • IL-5: stimulates IgA production.
  • IL-6: stimulates aKute-phase protein production.
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5
Q

IL-1

A
  • Secreted by macrophages
  • An endogenous pyrogen, also called osteoclast-activating factor.
  • Causes fever, acute inflammation.
  • Activates endothelium to express adhesion molecules
  • Induces chemokine secretion to recruit leukocytes.
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6
Q

IL-6

A
  • Secreted by macrophages
  • An endogenous pyrogen.
  • Also secreted by Th2 cells.
  • Causes fever and stimulates production of acute-phase proteins.
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7
Q

IL-8

A
  • Secreted by macrophages
  • Major chemotactic factor for neutrophils.
  • Neutrophils are recruited by IL-8 to clear infections.
    • “Clean up on aisle 8.”
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8
Q

IL-12

A
  • Secreted by macrophages
  • Induces differentiation of T cells into Th1 cells.
  • Activates NK cells.
  • Also secreted by B cells.
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9
Q

TNF-a

A
  • Secreted by macrophages
  • Mediates septic shock.
  • Activates endothelium.
  • Causes leukocyte recruitment, vascular leak.
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10
Q

IL-2

A
  • Secreted by all T cells
  • Stimulates growth of helper, cytotoxic, and regulatory T cells.
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11
Q

IL-3

A
  • Secreted by all T cells
  • Supports the growth and differentiation of bone marrow stem cells.
  • Functions like GM-CSF.
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12
Q

Interferon-γ

A
  • From Th1 cells
  • Has antiviral and antitumor properties.
  • Activates NK cells to kill virus-infected cells
  • Increases MHC expression and antigen presentation in all cells.
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13
Q

IL-4

A
  • From Th2 cells
  • Induces differentiation into Th2 cells.
  • Promotes growth of B cells.
  • Enhances class switching to IgE and IgG.
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14
Q

IL-5

A
  • From Th2 cells
  • Promotes differentiation of B cells.
  • Enhances class switching to IgA.
  • Stimulates the growth and differentiation of eosinophils.
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15
Q

IL-10

A
  • From Th2 cells
  • Modulates inflammatory response.
  • Inhibits actions of activated T cells and Th1.
  • Also secreted by regulatory T cells.
  • TGF-β has similar actions to IL-10, because it is involved in inhibiting inflammation.
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16
Q

Interferon α and β

A
  • A part of innate host defense against both RNA and DNA viruses.
  • Interferons are glycoproteins synthesized by viral-infected cells that act locally on uninfected cells, “priming them” for viral defense.
    • Interferes with viruses.
  • When a virus infects “primed” cells, viral dsRNA activates:
    • RNAase L Ž–> degradation of viral/host mRNA.
    • Protein kinase –>Ž inhibition of viral/host protein synthesis.
  • Essentially results in apoptosis, thereby interrupting viral amplification.
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17
Q

Cell surface proteins

  • All except mature RBCs have…
  • T cells
  • Helper T cells
  • Cytotoxic T cells
  • B cells
  • Macrophages
  • NK cells
A
  • All cells except mature RBCs have MHC I.
  • T cells
    • TCR (binds antigen-MHC complex)
    • CD3 (associated with TCR for signal transduction)
    • CD28 (binds B7 on APC)
  • Helper T cells
    • CD4, CD40 ligand
  • Cytotoxic T cells
    • CD8
  • B cells
    • Ig (binds antigen)
    • CD19, CD20, CD21 (receptor for EBV), CD40
    • MHC II, B7
    • You can drink Beer at the Bar when you’re 21
      • ​__B cells, Epstein-Barr virus; CD-_21_.
  • Macrophages
    • CD14, CD40
    • MHC II, B7
    • Fc and C3b receptors (enhanced phagocytosis)
  • NK cells
    • CD16 (binds Fc of IgG)
    • CD56 (unique marker for NK)
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18
Q

Anergy

A
  • Self-reactive T cells become nonreactive without costimulatory molecule.
  • B cells also become anergic, but tolerance is less complete than in T cells.
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19
Q

Effects of bacterial toxins

  • Superantigens
  • Endotoxins/lipopolysaccharide
A
  • Superantigens (S. pyogenes and S. aureus)
    • Cross-link the β region of the T-cell receptor to the MHC class II on APCs.
    • Can activate any T cell, leading to massive release of cytokines.
  • Endotoxins/lipopolysaccharide (gram-negative bacteria)
    • Directly stimulate macrophages by binding to endotoxin receptor CD14
    • Th cells are not involved.
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20
Q

Antigenic variation

  • Classic examples
    • Bacteria
    • Virus
    • Parasites
  • Some mechanisms for variation
A
  • Classic examples:
    • Bacteria
      • Salmonella (2 flagellar variants)
      • Borrelia (relapsing fever)
      • Neisseria gonorrhoeae (pilus protein).
    • Virus
      • Influenza (major = shift, minor = drift).
    • Parasites
      • Trypanosomes (programmed rearrangement).
  • Some mechanisms for variation
    • DNA rearrangement
    • RNA segment reassortment (e.g., influenza major shift).
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21
Q

Passive vs. active immunity

  • Means of acquisition
  • Onset
  • Duration
  • Examples
  • Notes
A
  • Means of acquisition
    • P: Receiving preformed antibodies
    • A: Exposure to foreign antigens
  • Onset
    • P: Rapid
    • A: Slow
  • Duration
    • P: Short span of antibodies (half-life = 3 weeks)
    • A: Long-lasting protection (memory)
  • Examples
    • P: IgA in breast milk, maternal IgG crossing placenta, antitoxin, humanized monoclonal antibody
    • A: Natural infection, vaccines, toxoid
  • Notes
    • P: After exposure to Tetanus toxin, Botulinum toxin, HBV, or Rabies virus, patients are given preformed antibodies (passive)
      • “To Be Healed Rapidly”
    • A: Combined passive and active immunizations can be given for hepatitis B or rabies exposure
22
Q

Vaccination

  • Vaccines
  • Live attenuated vaccine vs. Inactivated or killed vaccine
    • Description
    • Pros
    • Cons
    • Examples
A
  • Vaccines
    • Used to induce an active immune response (humoral and/or cellular) to specific pathogens.
  • Live attenuated vaccine vs. inactivated or killed vaccine
    • Description
      • L: Microorganism loses its pathogenicity but retains capacity for transient growth within inoculated host.
        • Mainly induces a cellular response.
      • I/K: Pathogen is inactivated by heat or chemicals
        • Maintaining epitope structure on surface antigens is important for immune response.
        • Humoral immunity induced.
    • Pros
      • L: Induces strong, often lifelong immunity.
      • I/K: Stable and safer than live vaccines.
    • Cons
      • L: May revert to virulent form.
        • Often contraindicated in pregnancy and immune deficiency.
      • I/K: Weaker immune response
        • Booster shots usually required.
    • Examples
      • L: Measles, mumps, rubella, polio (Sabin), influenza (intranasal), varicella, yellow fever.
      • I/K: Cholera, hepatitis A, polio (Salk), influenza (injection), rabies.
23
Q

Type I hypersensitivity

  • Reaction
  • Types I, II, and III
  • Test
A
  • Reaction
    • Anaphylactic and atopic—free antigen crosslinks IgE on presensitized mast cells and basophils, triggering immediate release of vasoactive amines that act at postcapillary venules (i.e., histamine).
    • Reaction develops rapidly after antigen exposure because of preformed antibody.
    • Delayed response follows due to production of arachidonic acid metabolites (e.g., leukotrienes).
    • First (type) and Fast (anaphylaxis).
  • Types I, II, and III
    • All antibody mediated.
  • Test
    • Skin test for specific IgE.
24
Q

Type II hypersensitivity

  • Reaction
  • Mechanisms
  • Test
A
  • Reaction
    • Cytotoxic (antibody mediated)
    • IgM, IgG bind to fixed antigen on “enemy” cell, leading to cellular destruction.
    • Antibody and complement lead to membrane attack complex (MAC).
    • Type II is cy-_2_-toxic.
  • 3 mechanisms:
    • ƒƒOpsonization leading to phagocytosis or complement activation
    • Complement-mediated lysis
    • Antibody-dependent cell-mediated cytotoxicity, usually due to NK cells or macrophages
  • Test
    • Direct Coombs’: detects antibodies that have adhered to patient’s RBCs (e.g., test an Rh (+) infant of an Rh (-) mother).
    • Indirect Coombs’: detects antibodies that can adhere to other RBCs (e.g., test an Rh (-) woman for Rh (+) antibodies).
25
Q

Type III hypersensitivity

  • Reaction
  • Serum sickness
  • Arthus reaction
  • Test
A
  • Immune complex
    • Antigen-antibody (IgG) complexes activate complement, which attracts neutrophils
    • Neutrophils release lysosomal enzymes.
    • In type III reaction, imagine an immune complex as 3 things stuck together: antigen-antibody-complement.
  • Serum sickness
    • An immune complex disease (type III) in which antibodies to the foreign proteins are produced (takes 5 days).
    • Immune complexes form and are deposited in membranes, where they fix complement (leads to tissue damage).
    • More common than Arthus reaction.
    • Most serum sickness is now caused by drugs (not serum) acting as haptens.
    • Fever, urticaria, arthralgias, proteinuria, lymphadenopathy 5–10 days after antigen exposure.
  • Arthus reaction
    • A local subacute antibody-mediated hypersensitivity (type III) reaction.
    • Intradermal injection of antigen induces antibodies, which form antigen-antibody complexes in the skin.
    • Characterized by edema, necrosis, and activation of complement.
    • Antigen-antibody complexes cause the Arthus reaction.
  • Test
    • Immunofluorescent staining.
26
Q

Type IV hypersensitivity

  • Reaction
  • Test
  • Mnemonic
A
  • Delayed (T-cell-mediated) type
    • Sensitized T lymphocytes encounter antigen and then release lymphokines
      • Leads to macrophage activation
      • No antibody involved
    • Cell mediated
      • Therefore, it is not transferable by serum.
    • 4th and last—delayed.
  • Test
    • Patch test, PPD.
  • 4 T’s
    • T lymphocytes
    • Transplant rejections
    • TB skin tests
    • Touching (contact dermatitis).
27
Q

Hypersensitivity types (mnemomnic)

A
  • ACID
  • Anaphylactic and Atopic (type I)
  • Cytotoxic (antibody mediated) (type II)
  • Immune complex (type III)
  • Delayed (cell mediated) (type IV)
28
Q

Hypersensitivity disorders

  • For each
    • Examples
    • Presentation
  • Type I
  • Type II
  • Type III
  • Type IV
A
  • Type I
    • Examples
      • Anaphylaxis (e.g., bee sting, some food/drug allergies)
      • Allergic and atopic disorders (e.g., rhinitis, hay fever, eczema, hives, asthma)
    • Presentation
      • Immediate, anaphylactic, atopic
  • Type II
    • Examples
      • Autoimmune hemolytic anemia
      • Pernicious anemia
      • Idiopathic thrombocytopenic purpura
      • Erythroblastosis fetalis
      • Acute hemolytic transfusion reactions
      • Rheumatic fever
      • Goodpasture syndrome
      • Bullous pemphigoid
      • Pemphigus vulgar
    • Presentation
      • Disease tends to be specific to tissue or site where antigen is found
  • Type III
    • Examples
      • SLE
      • Polyarteritis nodosa
      • Poststreptococcal glomerulonephritis
      • Serum sickness
      • Arthus reaction (e.g., swelling and inflammation following tetanus vaccine)
    • Presentation
      • Can be associated with vasculitis and systemic manifestations
  • Type IV
    • Examples
      • Multiple sclerosis
      • Guillain-Barré syndrome
      • Graft-versus-host disease
      • PPD (test for M. tuberculosis)
      • Contact dermatitis (e.g., poison ivy, nickel allergy)
    • Presentation
      • Response is delayed and does not involve antibodies (vs. types I, II, and III)
29
Q

Blood transfusion reactions

  • For each
    • Pathogenesis
    • Clinical presentation
  • Allergic reaction
  • Anaphylactic reaction
  • Febrile nonhemolytic transfusion reaction
  • Acute hemolytic transfusion reaction
A
  • Allergic reaction
    • P: Type I hypersensitivity reaction against plasma
      proteins in transfused blood.
    • C: Urticaria, pruritus, wheezing, fever.
      • Treat with antihistamines.
  • Anaphylactic reaction
    • P: Severe allergic reaction.
      • IgA-deficient individuals must receive blood products that lack IgA.
    • C: Dyspnea, bronchospasm, hypotension, respiratory arrest, shock.
  • Febrile nonhemolytic transfusion reaction
    • P: Type II hypersensitivity reaction.
      • Host antibodies against donor HLA antigens and leukocytes.
    • C: Fever, headaches, chills, flushing.
  • Acute hemolytic transfusion reaction
    • P: Type II hypersensitivity reaction.
      • Intravascular hemolysis (ABO blood group incompatibility) or extravascular hemolysis (host antibody reaction against foreign antigen on donor RBCs).
    • C: Fever, hypotension, tachypnea, tachycardia, flank pain, hemoglobinemia (intravascular), jaundice (extravascular hemolysis).
30
Q

Associated disorders of these autoantibodies

  • Anti-ACh receptor
  • Anti-basement membrane
  • Anti-cardiolipin, lupus anticoagulant
  • Anticentromere
  • Anti-desmoglein
  • Anti-dsDNA, anti-Smith
  • Anti-glutamate decarboxylase
  • Anti-hemidesmosome
  • Antihistone
  • Anti-Jo-1, anti-SRP, anti-Mi-2
  • Antimicrosomal, antithyroglobulin
  • Antimitochondrial
  • Antinuclear antibodies
  • Anti-Scl-70 (anti-DNA topoisomerase I)
  • Anti-smooth muscle
  • Anti-SSA, anti-SSB (anti-Ro, anti-La)
  • Anti-TSH receptor
  • Anti-U1 RNP (ribonucleoprotein)
  • c-ANCA (PR3-ANCA)
  • IgA antiendomysial, IgA anti-tissue transglutaminase
  • p-ANCA (MPO-ANCA)
  • Rheumatoid factor (antibody, most commonly IgM, specific to IgG Fc region), anti-CCP
A
  • Anti-ACh receptor
    • Myasthenia gravis
  • Anti-basement membrane
    • Goodpasture syndrome
  • Anti-cardiolipin, lupus anticoagulant
    • SLE, antiphospholipid syndrome
  • Anticentromere
    • Limited scleroderma (CREST syndrome)
  • Anti-desmoglein
    • Pemphigus vulgaris
  • Anti-dsDNA, anti-Smith
    • SLE
  • Anti-glutamate decarboxylase
    • Type 1 diabetes mellitus
  • Anti-hemidesmosome
    • Bullous pemphigoid
  • Antihistone
    • Drug-induced lupus
  • Anti-Jo-1, anti-SRP, anti-Mi-2
    • Polymyositis, dermatomyositis
  • Antimicrosomal, antithyroglobulin
    • Hashimoto thyroiditis
  • Antimitochondrial
    • 1° biliary cirrhosis
  • Antinuclear antibodies
    • SLE, nonspecific
  • Anti-Scl-70 (anti-DNA topoisomerase I)
    • Scleroderma (diffuse)
  • Anti-smooth muscle
    • Autoimmune hepatitis
  • Anti-SSA, anti-SSB (anti-Ro, anti-La)
    • Sjögren syndrome
  • Anti-TSH receptor
    • Graves disease
  • Anti-U1 RNP (ribonucleoprotein)
    • Mixed connective tissue disease
  • c-ANCA (PR3-ANCA)
    • Granulomatosis with polyangiitis (Wegener)
  • IgA antiendomysial, IgA anti-tissue transglutaminase
    • Celiac disease
  • p-ANCA (MPO-ANCA)
    • Microscopic polyangiitis, Churg-Strauss syndrome
  • Rheumatoid factor (antibody, most commonly IgM, specific to IgG Fc region), anti-CCP
    • Rheumatoid arthritis
31
Q

Infections in immunodeficiency

  • B-cell vs. T-cell deficiencies
  • Bacteria
    • No T cells
    • No B cells
    • No granulocyte
    • No complement
  • Virus
    • No T cells
    • No B cells
  • Fungi/parasites
    • No T cells
    • No B cells
    • No granulocyte
A
  • B-cell vs. T-cell deficiencies
    • B-cell deficiencies tend to produce recurrent bacterial infections
    • T-cell deficiencies produce more fungal and viral infections.
  • Bacteria
    • No T cells: Sepsis
    • No B cells: Encapsulated (SHiNE SK**i**S)
      • Streptococcus pneumoniae
      • Haemophilus influenzae type B
      • Neisseria meningitidis
      • Escherichia coli
      • Salmonella
      • Klebsiella pneumoniae
      • Group B Strep
    • No granulocyte: Staphylococcus, Burkholderia cepacia, Serratia, Nocardia
    • No complement: Neisseria (no membrane attack complex)
  • Virus
    • No T cells: CMV, EBV, JCV, VZV chronic infection with respiratory/GI viruses
    • No B cells: Enteroviral encephalitis, poliovirus (live vaccine contraindicated)
  • Fungi/parasites
    • No T cells: Candida, PCP
    • No B cells: GI giardiasis (no IgA)
    • No granulocyte: Candida, Aspergillus
32
Q

X-linked (Bruton) agammaglobulinemia

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B-cell disorder
  • Defect
    • Defect in BTK, a tyrosine kinase gene Ž–> no B cell maturation.
    • X-linked recessive (increase in Boys).
  • Presentation
    • Recurrent bacterial and enteroviral infections after 6 months (decrease maternal IgG).
  • Findings
    • Normal CD19+ B cell count, decreased pro-B, decreased Ig of all classes.
    • Absent/scanty lymph nodes and tonsils.
33
Q

Selective IgA deficiency

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B-cell disorder
  • Defect
    • Unknown.
    • Most common 1° immunodeficiency.
  • Presentation
    • Majority Asymptomatic.
    • Can see Airway and GI infections, Autoimmune disease, Atopy, Anaphylaxis to IgA-containing products.
  • Findings
    • IgA < 7 mg/dL with normal IgG, IgM levels.
34
Q

Common variable immunodeficiency

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B-cell disorder
  • Defect
    • Defect in B-cell differentiation.
    • Many causes.
  • Presentation
    • Can be acquired in 20s–30s
    • Increased risk of autoimmune disease, bronchiectasis, lymphoma, sinopulmonary infections.
  • Findings
    • Decreased plasma cells
    • Decreased immunoglobulins.
35
Q

Thymic aplasia (DiGeorge syndrome)

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • T-cell disorder
  • Defect
    • 22q11 deletion
    • Failure to develop 3rd and 4th pharyngeal pouches Ž–> absent thymus and parathyroids.
  • Presentation
    • Tetany (hypocalcemia), recurrent viral/fungal infections (T-cell deficiency), conotruncal abnormalities (e.g., tetralogy of Fallot, truncus arteriosus).
  • Findings
    • Decreased T cells, decreased PTH, decreased Ca2+.
    • Absent thymic shadow on CXR.
    • 22q11 deletion detected by FISH.
36
Q

IL-12 receptor deficiency

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • T-cell disorder
  • Defect
    • Decreased Th1 response.
    • Autosomal recessive.
  • Presentation
    • Disseminated mycobacterial and fungal infections
    • May present after administration of BCG vaccine.
  • Findings
    • Decreased IFN-γ.
37
Q

Autosomal dominant hyper-IgE syndrome (Job syndrome)

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • T-cell disorder
  • Defect
    • Deficiency of Th17 cells due to STAT3 mutation –>Ž impaired recruitment of neutrophils to sites of infection.
  • Presentation
    • FATED: coarse Facies, cold (noninflamed) staphylococcal Abscesses, retained primary Teeth, increased IgE, Dermatologic problems (eczema).
  • Findings
    • Increased IgE, decreased IFN-γ.
38
Q

Chronic mucocutaneous candidiasis

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • T-cell disorder
  • Defect
    • T-cell dysfunction.
    • Many causes.
  • Presentation
    • Noninvasive Candida albicans infections of skin and mucous membranes.
  • Findings
    • Absent in vitro T-cell proliferation in response to Candida antigens.
    • Absent cutaneous reaction to Candida antigens.
39
Q

Severe combined immunodeficiency (SCID)

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B- and T-cell disorder
  • Defect
    • Several types including defective IL-2R gamma chain (most common, X-linked), adenosine deaminase deficiency (autosomal recessive).
  • Presentation
    • Failure to thrive, chronic diarrhea, thrush.
    • Recurrent viral, bacterial, fungal, and protozoal infections.
    • Treatment: bone marrow transplant (no concern for rejection).
  • Findings
    • Decreased T-cell receptor excision circles (TRECs).
    • Absence of thymic shadow (CXR), germinal centers (lymph node biopsy), and T cells (flow cytometry).
40
Q

Ataxia-telangiectasia

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B- and T-cell disorder
  • Defect
    • Defects in ATM gene Ž–> DNA double strand breaks –>Ž cell cycle arrest.
  • Presentation
    • Triad: cerebellar defects (Ataxia), spider Angiomas (telangiectasia), IgA deficiency.
  • Findings
    • Increased AFP.
    • Decreased IgA, IgG, and IgE.
    • Lymphopenia, cerebellar atrophy.
41
Q

Hyper-IgM syndrome

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B- and T-cell disorder
  • Defect
    • Most commonly due to defective CD40L on Th cells = class switching defect
    • X-linked recessive.
  • Presentation
    • Severe pyogenic infections early in life
    • Opportunistic infection with Pneumocystis, Cryptosporidium, CMV.
  • Findings
    • Increased IgM.
    • Decreased IgG, IgA, IgE.
42
Q

Wiskott-Aldrich syndrome

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • B- and T-cell disorder
  • Defect
    • Mutation in WAS gene (X-linked recessive)
    • T cells unable to reorganize actin cytoskeleton.
  • Presentation
    • WATER: Wiskott-Aldrich: Thrombocytopenic purpura, Eczema, Recurrent infections.
    • Increased risk of autoimmune disease and malignancy.
  • Findings
    • Decreased to normal IgG, IgM.
    • Increased IgE, IgA.
    • Fewer and smaller platelets.
43
Q

Leukocyte adhesion deficiency (type 1)

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • Phagocyte dysfunction
  • Defect
    • Defect in LFA-1 integrin (CD18) protein on phagocytes
    • Impaired migration and chemotaxis
    • Autosomal recessive.
  • Presentation
    • Recurrent bacterial skin and mucosal infections, absent pus formation, impaired wound healing, delayed separation of umbilical cord (>30 days).
  • Findings
    • Increased neutrophils.
    • Absence of neutrophils at infection sites.
44
Q

Chédiak-Higashi syndrome

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • Phagocyte dysfunction
  • Defect
    • Defect in lysosomal trafficking regulator gene (LYST).
    • Microtubule dysfunction in phagosome-lysosome fusion
    • Autosomal recessive.
  • Presentation
    • Recurrent pyogenic infections by staphylococci and streptococci, partial albinism, peripheral neuropathy, progressive neurodegeneration, infiltrative lymphohistiocytosis.
  • Findings
    • Giant granules in neutrophils and platelets.
    • Pancytopenia.
    • Mild coagulation defects.
45
Q

Chronic granulomatous disease

  • Type of disorder
  • Defect
  • Presentation
  • Findings
A
  • Type of disorder
    • Phagocyte dysfunction
  • Defect
    • Defect of NADPH oxidase –> decreasedŽ reactive oxygen species (e.g., superoxide) and absent respiratory burst in neutrophils
    • X-linked recessive.
  • Presentation
    • Increased susceptibility to catalase (+) organisms (PLACESS): Pseudomonas, Listeria, Aspergillus, Candida, E. coli, S. aureus, Serratia.
  • Findings
    • Abnormal dihydrorhodamine (flow cytometry) test.
    • Nitroblue tetrazolium dye reduction test is (-) (test out of favor).
46
Q

Grafts

  • Autograft
  • Syngeneic graft
  • Allograft
  • Xenograft
A
  • Autograft
    • From self.
  • Syngeneic graft
    • From identical twin or clone.
  • Allograft
    • From nonidentical individual of same species.
  • Xenograft
    • From different species.
47
Q

Hyperacute transplant rejection

  • Onset
  • Pathogenesis
  • Features
A
  • Onset
    • Within minutes
  • Pathogenesis
    • Pre-existing recipient antibodies react to donor antigen (type II reaction), activate complement.
  • Features
    • Widespread thrombosis of graft vessels –>Ž ischemia/necrosis.
    • Graft must be removed.
48
Q

Acute transplant rejection

  • Onset
  • Pathogenesis
  • Features
A
  • Onset
    • Weeks to months
  • Pathogenesis
    • Cellular: CTLs activated against donor MHCs.
    • Humoral: similar to hyperacute, except antibodies develop after transplant.
  • Features
    • Vasculitis of graft vessels with dense interstitial lymphocytic infiltrate.
    • Prevent/reverse with immunosuppressants.
49
Q

Chronic transplant rejection

  • Onset
  • Pathogenesis
  • Features
A
  • Onset
    • Months to years
  • Pathogenesis
    • Recipient T cells perceive donor MHC as recipient MHC and react against donor antigens presented.
    • Both cellular and humoral components.
  • Features
    • Irreversible.
    • T-cell and antibody-mediated damage.
    • Organ specific:
      • Heart—atherosclerosis.
      • Lungs—bronchiolitis obliterans.
      • Liver—vanishing bile ducts.
      • Kidney—vascular fibrosis, glomerulopathy.
50
Q

Graft-versus-host disease (transplant rejection)

  • Onset
  • Pathogenesis
  • Features
A
  • Onset
    • Varies
  • Pathogenesis
    • Grafted immunocompetent T cells proliferate in the immunocompromised host and reject host cells with “foreign” proteins –>Ž severe organ dysfunction.
  • Features
    • Maculopapular rash, jaundice, diarrhea, hepatosplenomegaly.
    • Usually in bone marrow and liver transplants (rich in lymphocytes).
    • Potentially beneficial in bone marrow transplant for leukemia (graft-versus-tumor effect).

First Aid (92 decks)

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