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37 Cards in this Set
- Front
- Back
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Components of innate immune system.
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Humoral
a. Complement b. Acute phase proteins c. Interferon Cell-mediated: a. Phagocytic cells (monocytes, macrophages, eosinophils, neutrophils, basophils) b. Natural Killer cells. |
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What does the innate system recognize>?
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pathogen-associated molecular patterns (PAMPS)
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Components of acquired immune system.
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Humoral
a. Antibodies Cell-Mediated: a. B lymphocytes b. T lymphocytes. |
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What is an immunogen?
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Any substance that can elicit an immune response.
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What is an antigen?
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Can bind or react with products of immune response. (doesn't necessary elicit immune response)
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Name 2 results of antigen binding to B cell.
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1. proliferation into antibody secreting plasma cells.
2. proliferation into memory cells. |
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Differentiate b/w primary and secondary lymphoid organs.
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Primary = bone marrow and thymus. (from stem cells).
Secondary = where immune system mets pathogen. |
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What is difference b/w complement and acute phase proteins?
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Complement = activated by contact c microbes and kills them.
Acute-phase: bind microbes and target them to phagocytic cells. |
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What do CD8+ cells recognize?
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MHC Class I, which is present on all nucleated cells.
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What do CD4+ recognize?
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MHC Class II which are expressed exclusively on the surfaces of "antigen-presenting cells" -- including macrophages, dendritic cells, and B cells ,
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Describe the 2 cell lineages produced by bone marrow.
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1. Granulocyte-macrophage lineage of innate immunity (monocytes, macrophages, neutrophils, basophils, eosinophils)
2. Lymphoid lineage (acquired immunity - T ,B, NK cells) |
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What indicates that a B cells in the lymph follicle has recently encountered antigen?
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Presence of a Germinal Center. This is the key area of B cell proliferation.
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Describe sequence of events in B cell development from stem cell to plasma cell.
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1. B cell produced by stem cells in bone marrow.
2. B/c mature and leaves bone marrow. 3. Is activated by antigen in secondary lymphoid tissue. 4. Clonal selection, expansion and differentiation to b/c plasma cell. 5. Antibody is released and eliminates foreign object. 6. Plasma cell dies. |
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Describe genetic mechanisms involved in generation of antibody diversity.
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Clonal selection. When angient is recognized, B cells proliferates and clonal expansion occurs.
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Describe heavy and light chain gene organization.
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Heavy: IgM,D,A,G,or E.
Has 2 identical chains. Each has 1 var, 1 constant region. Light: lambda or kappa. 2 identical chains. Each has 1 var, 1 constant region. |
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Describe order of rearrangement and expression of Ig heavy and light chain during B cell development.
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Heavy chain rearranged 1st.
Order is: 1. Heavy chain a. D-J b. V-DJ c. VDJ-c 2. Light a. V-J b. VJ-C |
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Define allelic exclusion.
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If DNA rearrangment is productive, there is (-) feedback by protein at cell surface to prevent rearrangement
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Define isotype switching.
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INcreases the functional diversity of Ig molecules. Different isotypes have different biological functions, but can have same antigen affinity.Occurs in secondary lymphoid organs.
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Where does somatic recombination occur.
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in the progenitor cell as it is becoming a B cell in bone marrow.
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Differentiate b/w transmembrane and secreted immunoglobulin.
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All B cells initially express the transmembrane form of IgM; after antigen stimulation, some of their progeny differentiate into plasma cells producing the secreted form of IgM, whereas others undergo isotype switching to express transmembrane immunoglobulins of a different isotype before switching to the production of secreted antibody of the new isotype.
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What part of B cell development is antigen-independent? dependent?
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Independent = IgG and IgD.
Dependent - Transmembrane IgM changes to secreted IgM. Helper T cells stimlate isotype switching. Affinity maturation. |
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Describe structure of T cell receptor.
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Heterodimer b/w alpha and beta chain or delta/gamma. External portion has both V and C regions. Transmembrane helices contain (+)charged residues w/i hydrophobic transmembrane segment.
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Distinguish b/w alpha-beta and gamma-delta TCR.
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Alpha/Beta go through normal maturational path. Always assoc with CD3. Involve both CD4 and CD8.
Delta/Gamma develop directly from stem cell (none of the double -,double+ steps). React with lipid antigens and microbacteria. Higher in newborns. |
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Which cells (B or T) undergo somatic mutation?
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B cells.
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What is CDR3?
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The most variable of thge hypervariable regions on the V Chain of T cell receptor.
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Describe maturational stages of T cells.
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Bone marrow to thymus (double negative, then doulbe positive, then double positive with alpha/beta and CD3, then single positive and released to blood and tissue.
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Describe T cell receptor-CD3 complex and the molecule involved.
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CD3 complex has longer cytoplasmic domains which do signal transduction. Aspartic acid in the transmembrane domain provides negative charge which complements the positive charge in transmembrane domain of TCR and helps stabilize it.
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When is CD3 added to the T cell?
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After it becomes double positive in the thymus. CD3 and TCRalpha-beta are added at same time.
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Describe T-independent and dependent antigens.
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Independent: stimulate B cell proliferation/diff into plasma cells w/o T cells. Usually is viral antigen. Lipopolysacc from gram neg. bacteria is one. Can act as B cell mitogens (stimulate B cells in polyclonal way.) Produces IgM. Little memory or affinity maturation.
Dependent: Antigens stimulate T cells which stimulate B cells. |
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Describe positive and negative selection of T cells.
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During positive selection Double-Positive T cells that can recognize self MHC's are selected for proliferation, and those T cells that do not recognize self MHC die via Apoptosis.
Negative: those T cells that are strongly activated by self MHC plus self peptides need to be eliminated in the thymus. If they escape this elimination, they may subsequently react against self antigens, and cause Autoimmune disease |
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Describe function of MHC molecules in antigen prsentation.
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The antigen presenting cells such as macrophages and B-cells take up antigen and partially degrade it into peptides which then occupy the antigen-presenting groove in MHC-I (AB &C)and MHC-II (D)molecules.
There are two classes of MHC molecule 1) MHC class I , which primarily present intracellular antigens. 2) MHC class II , which primarily present extracellular antigens |
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Describe structural features of MHC Class 1.
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Has 3 domains (alpha1 and 2, Beta sheet) and transmembrane domains with cytoplasmic tail.
Always associated with beta-2 microglubulin which is required for structural stability. They present molecules synethesized inside the cell (viruses). |
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Describe structural features of MHC Class 2.
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Have a DP,DQ,DR region.
Present extracellular (soluble) antigen. |
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Identify the cellular tissue distribution of class I and class II MHC molecules.
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Class I: all nucleated cells.
Class II: marcophages & dendritic cells. |
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Explain MHC polymophism and the selective advantage of this system.
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Codominant expression. one set from mother, one from father.
MHC class I a subunits are encoded by polymorphic MHC genes while the common b subunit is encoded by the conserved, non-MHC gene for b2-microglobulin (b2m). Both MHC class II a and b subunits are encoded by polymorphic MHC genes. |
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What is MHC restriction?
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T cell activation requires binding of both antigen and MHC.
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Define haplotype.
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Alleles that occur together on a single chromosome. In codominant expression, all alleles from both mother and father are expressed.
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