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Q: Name two binding interactions necessary for T cell proliferation and differentiation.
A: TCR:MHC-antigen and CD28:B7
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Q: What is the primary cytokine responsible for T cell proliferation and differentiation?
A: IL-2
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Q: True or False TCRs are MHC restricted and antigen specific?
A: True
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Q: TCRs are made up of how many different proteins? What are their names and the associations?
A: 4, alpha:beta and gamma:delta
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Q: Which TCR chains contain D regions?
A: beta and delta
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Q: How many core heterodimers does each TCR contain?
A: one, either alpha:beta or gamma:delta
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Q: Distortion upon seeing MHC:antigen leads to what?
A: CD3 activation signaling
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Q: What are the two co-receptor molecules for T cells and which is more common?
A: CD4 and CD8; CD4 is more common (65%)
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Q: Which MHC do CD4 and CD8 T cells recognize and what are they more commonly known as, respectively?
A: CD4: MHC II, helper T CD8: MHC I, CTL or cytotoxic T cell
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Q: What are the effector functions of helper T and cytotoxic T cells, respectively?
A: secrete cytokines(helper); kill target cells(CTL)
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Q: Name the eight polypeptides that compose the complete TCR complex
A: one core heterodimer, either alpha:beta or gamma:delta; two CD3 dimers (1 CD3gamma, 1CD3delta, 2CD3epsilon), 2 zeta chains
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Q: How do we generate an immune response (via T cells) that recognizes foeign antigen, but not self-antigen?
A: There 2 discrete processes: positive selection and negative selection of maturing B cells.
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Q: What are nurse cells and where are they located?
A: dendritic-like cells in the thymus.
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Q: What are the 2 zones of the thymus?
A: outer cortex and inner medulla
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Q: What kind of T cells are located in wach zone?
A: Most mature cells in medulla and the least mature in the cortex.
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Q: What key marker do the most immature thymocytes lack?
A: CD3
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Q: In TCR rearrangement, which chains rearrange first?
A: gamma/delta
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Q: When is transcription of CD3 stimulated?
A: Once the TCR genes start to rearrange.
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Q: What markers do a double positive cell have?
A: CD4 and CD8
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Q: What are T cells saved from if they are positively selected?
A: Death by apoptosis.
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Q: What is the instructional model of positive selection?
A: Double positive cells bind either MHC I or MHC II with the TCR. If a close enough match, CD4 or CD8 will engage, leading to of the un-untilized chain.
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Q: What is the stochastic model of positive selection?
A: Double positive cells randomly lose the expression of either CD4 or CD8, then must engage a MHC class I or class II correctly or the cell will die.
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Q: What is the purpose of negative selection?
A: Removal from the population of T cells those that recognize self MHC when occupied by self antigen.
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Q: What happens if a self reactive T cell is not removed by negative selection?
A: That T cell can help B cells produce auto reactive anitbodies, or make CTL’s that kill normal, healthy self cells.
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Q: How are T cells that are self reactive eliminated?
A: apoptosis.
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Q: What are all naïve, un-activated T cells known as?
A: TH0 cells
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Q: What happens if a TH0 cell is activated in the presence of IL-4?
A: It will become a TH2 cell.
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Q: What happens if a TH0 cell is activated in the presence of IL-12?
A: It will become a TH1 cell.
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Q: What do TH1 cells produce, and what immune response does this drive?
A: IFN-gamma; antibacterial inflammatory response
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Q: What is involvet in the antibacterial inflammatory respone?
A: production of opsonizing isotypes of antibody, activation of macrophages, enhanced CTL, NK and neutrophil killing.
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Q: What do TH2 cells produce?
A: IL-4, IL-5, IL-10
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Q: What are these IL’s involved in?
A: Neutralizing, and part of the allergic response. IL-5 leads to eosinophil proliferation and activation, also push macrophages into anti-inflammatory status.
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Q: List 6 functions of cell mediated immunity in host defense.
A: viral immunity, fungal immunity, Ab production against T-dependent antigens, homograft rejection, protection against intracellular bacterial infections, tumor surveillance
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Q: What are the three tests used to determine immunity?
A: delayed skin hypersensitivity, T cell quantification - different types, Mitigic assay (LAM)
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Q: What is SCID?
A: Severe Combined Immune Deficiency
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Q: List 3 SCID diseases?
A: 1)X-linked SCID, 2)Autosomal recessive SCID due to ADA, PNP deficiency, 3)Autosomal recessive SCID due to other causes
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Q: What other things can you measure to determine immune status?
A: cytokine production, presence
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Q: What are some clinical characteristics of SCID?
A: Multiple conditions; recurrent infections, viral respiratory infections, candidasis, pneumocystis, pertussis couph, diarrhea, intracellular bacti infections, pogenic bacti infections post 6 mo. Old.
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Q: What happens if there is a loss of ADA, adenosine deaminase?
A: there is a build up of purines, to toxic levels
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Q: What is the significance of not having MHC class I or II expression?
A: Cannot present antigens
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Q: What happens in Purine Metabolic Pathway Abnormalities?
A: Build up of toxic products
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Q: Adenosine deaminase deficiency is seen in 20% of SCID patients, what does it do?
A: catalyzes adenosine and deoxyadenosine to inosine and 2'deoxyinosine
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Q: The build up of adenosine and deoxyadenosine is toxic to what structures?
A: lymphocytes
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Q: There is a condition in the purine metabolism pathway that results in mostly the destruction of T cells, what is it called?
A: Purine Nucleoside Phosphorylase Deficiency
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Q: What is X-linked SCIDS
A: NO T cell production, normal or increased B cell production, reduced serum Ig
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Q: What is the defect in X-linked SCIDS?
A: mutation in gene for gamma chain of IL-2 receptor
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Q: What does the IL-2 receptor have to do with T cell production?
A: mediates growth via multiple cytokine production, IL2, IL4, IL7, IL15
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Q: Why does an X-linked SCID patient also have poor antibody production?
A: T cells help instruct the production of antibodies
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Q: T cell maturation defects are rare, what is the most frequent disease seen?
A: Di George Syndrome
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Q: What is Di George Syndrome?
A: Thymic hypolasia
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Q: What is thymic hypoplasia?
A: Abnormal or No thymus development, abnormality of third and fourth pharyngeal pouch, which leads to decreased T cell maturation
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Q: What are some characteristics that should signal Di George Syndrome (6+)?
A: seizures, hypocalcemia, heart murmur, peculiar facies, cleft palate, recurrent infections
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Q: What is Wiskott-Aldrich Syndrome?
A: combined T and B cell deficiency
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Q: Is Wiskott-Aldrich Syndrome X-linked?
A: yes
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Q: List symptoms of Wiskott-Aldrich Syndrome (6+).
A: can't walk or maintain balance, eczema, thrombocytopenia, bleeding, bruising, recurring infections, ataxia, telangiectasia
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Q: Why do you see the bruising and bleeding in the Wiskott-Aldrich Syndrome?
A: poor platelet size and function, therefore poor clotting
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Q: What is telangiectasia?
A: dilation of small or terminal vesicles, bloody rash or spots in eyes and on skin, associated with Wiskott-Aldrich
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Q: What is ataxia?
A: inability to coordinate muscle activity
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Q: Why can X-raying a Wiskott-Aldrich patient result in a possible malignant tumor growth?
A: they have DNA repair failures
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Q: What is the Bare Lymphocyte Syndrome?
A: no MHC II expression
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Q: What deficiency is seen in Bare Lymphocyte Syndrome?
A: loss of helper T cells, CD4, decrease in T cell dependent humoral immunityty
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