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What does the thoracic duct drain into?
Left subclavian
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Positive T cell selection
- Selects for T cells that can bind MHC
- Occurs in cortex of thymus
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Negative T cell selection
- Selects for autoreactive T cells
- Occurs in medulla of thymus
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Where are small antigenic peptides attached to MHC I?
RER
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What is significant about CD5+ B cells?
They have not undergone class switching, and can only produce IgM
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Function of perforin and granzymes
- Perforin delivers NK cell granule contents into infected cells
- Granzyme activates serine proteases, which triggers apoptosis
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What activates T helper cells?
Foreign antigen presentation on MHC II, with help of B7 costimulatory molecule
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Which MHC activates cytotoxic T cells?
MHC I (presents viral or self antigens)
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Where is the CD40 ligand located, and what does it do?
- CD 40 ligand on T helper cell membrane
- Mediates AB class switching
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Function of immunoglobulins alpha and beta on B cell membrane
Transduce AG binding signal to cytoplasm
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Difference between pro-B cells and pre-B cells
- Heavy chain rearrangement occurs in pro-B cells
- Light chain rearrangement occurs in pre-B cells
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tDt
- Randomly inserts nucleotides between D and J regions during DNA synthesis to increase affinity of AB for AG
- Used as a marker for ALL
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Which antibody does not undergo somatic hypermutation?
IgM
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What is a thymus independent antigen?
Thymus independent antigens lack a peptide component, so cannot be presented by MHC to T cells. They stimulate release of IgM only, and do not activate memory
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EBV receptor
CD21, found on B cells
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Primary opsonins
C3b and IgG
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C3 deficiency
- Recurrent pyogenic and respiratory infections
- Increased susceptibility to type III hypersensitivity reactions
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DAF deficiency
DAF helps prevent complement activation against self-cells. Is deficient in PNH.
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How do interferons kill viruses?
They induce production of a ribonuclease that degrades viral mRNA
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What type hypersensitivity reaction are serum sickness and arthus reaction?
- Type III
- Present with fever, urticaria, and arthralgias, 5--10 days after antigen exposure
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Hypersensitivity reactions: Grave's and Hashimoto's
- Graves--type II
- Hashimoto's--type IV
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What are the type IV hypersensitivity reactions?
- Diabetes I
- Celiac
- Guilliane-Barre
- Hashimoto's
- MS
- GVHD
- PPD
- Contact dermatitis
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6 month old boy presents with recurrent bacterial infections, decreased B cells, and decreased immunoglobulins
- Bruton's agammaglobulinemia
- Defect in BTK tyrosine kinase gene
- XR
- B cell maturation is impaired
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Baby presents with severe pyogenic infections and increased IgM with no other immunoglobulins
- HyperIgM
- Caused by defective CD40 ligand on T helper cells
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Patient with a history of respiratory infections experience anaphylaxis after a blood transfusion
- Selective Ig deficiency, due to defective class switching
- Most common is IgA deficiency
- Patients often develop antibodies against the missing Ig--so don't transfuse!
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Which Ig do Di George patients have?
IgM only, since T cells are needed for class switching
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Patient has recurrent disseminated mycobacterial infections and low interferon gamma
- IL12 receptor deficiency
- (IL12 is secreted by macrophages and activates T helper 1 cells)
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Patient presents with staphylococcal abscesses, retained primary teeth, eczema, and increased IgE
- HyperIgE/Job's syndrome
- T helper cells cannot produce interferon gamma, which inhibits neutrophil response to chemotactic stimuli
- Normally, IFN gamma inhibits T helper 2 cells--too many T helper 2 cells results in elevated IgE
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Primary defense against cutaneous and hematogenous candida infection
- T cells protect against cutaneous candida
- Neutrophils protect against disseminated candida
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Name 3 causes of SCID
- Defective IL2 receptor (X linked)
- Adenosine deaminase deficiency
- Missense mutation in RAG
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Patient presents with TTP, recurrent infection, and truncal eczema.
- Wiskott-Aldrich
- Progressive B and T cell deletion, due to an XR mutation in cytoskeleton proteins
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Patient presents with cerebellar ataxia, spider angiomas, and IgA deficiency
Ataxia telangiectasia, caused by defective DNA repair enzymes
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A baby presents with recurrent bacterial infections and delayed separation of umbilicus
- LAD
- Defective integrin protein on phagocytes impair ability of leukocytes to adhere to endothelium
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Patient presents with recurrent staph and strep infections, pale skin, and peripheral neuropathy
- Chediak-Higashi
- An AR defect in microtubule function impairs phagocytosis
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Patient presents with a history of recurrent infections by catalase positive organisms (staph, E. coli, aspergillus)
Addition of nitroblue tetrazolium to blood sample does not make sample turn blue
- CGD
- Due to lack of NADPH oxidase
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Mechanism and side effect of cyclosporine
- Inhibits calcineurin, which prevents release of IL2, thereby blocking T cell activation
- Major side effect is nephrotoxicity, which can be controlled with mannitol diuresis
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Mechanism and side effects of tacrolimus
- Binds to FK binding protein and inhibits IL2 release
- Causes nephrotoxicity, peripheral neuropathy, and hyperglycemia
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Muromonab
Monoclonal antibody against CD3, inhibits T cell signal transduction
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Sirolimus (rapamycin)
- Binds to MTOR, inhibits T cell proliferation in response to IL2
- Causes hyperlipidemia
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Mycophenolate mofetil (MMP)
Inhibits de novo guanine synthesis
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Daclizumab/Basiliximab
Monoclonal antibody against IL2 receptor
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What is oprelvekin used for?
Thrombocytopenia
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