Fundamentals I Test 4 Burrows – Flashcards
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| In what two forms are Ab's found? |
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| Attached to B-cell membranes or Secreted by Plasma cells |
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| T/F; Edelman ; Porter used ultracentrifugation, Papain digestion, Pepsin digestion, ; Mercaptoethanol to break down IgG and discover it's structure. |
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| True |
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| What connects the heavy and light chains of IgG? |
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| Disulfide Bonds |
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| On what end of the light chain do you find the constant & variable regions? In which region do you find kappa or lambda types? |
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Constant: C-terminal, kappa & lambda Variable: N-terminal |
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| How many basic sequence patterns are found on the heavy chain constant region? |
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| 5 |
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| What defines the isotype of an Ab? |
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| The heavy chain type (IgM, IgG, IgA, IgD, IgE) |
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| What are the Ag-binding sites of Abs, and where are they found? |
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| Hypervariable or Complementary-Determining Regions; on the variable portion of the heavy & light chains |
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| T/F CDR's are not found adjacent on the primary structure, but they are adjacent in the secondary structure. |
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| True; they fold to be in the same area |
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| What is the term for the Ag Determinant binding site? |
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| Epitope |
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| What gives the Hinge region its flexibility, what is it susceptible to, and in what Ig's is it found? |
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| Flexibility - Proline Residues; Susceptible - Proteolytic Enzymes; IgG, IgD, and IgA |
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| What is the most abundant Ig in serum? What is its structure? |
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| IgG; monomer of 2γ H-Chains and 2κ or λ L-Chains |
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| How many subclasses does IgG have & what makes them different? |
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| 4 (numbered by their serum concentration); size of hinge region & number and position of interchain S-S bonds b/w H-chains |
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| Which Immunoglobulin molecule is pentameric and has 10 potential Ag-binding sites? |
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| IgM |
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| Which Ab is the first produced during primary immune response and is the Ag receptor on B cells? |
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| IgM |
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| What is the predominant Ig class in mucosal secretions? In what forms does it exist? |
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| IgA; monomeric in serum & dimeric/tetrameric in secretions |
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| What is the main effector Ab in mucosal secretions, and how is it formed? |
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| S-IgA; IgA binds pIgR and is internalized, a portion is then cleaved leaving the other portion bound to IgA which forms S-IgA |
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| Which type of Ab mediates Type 1 hypersensitivity reactions and binds Fc receptor of basophils & mast cells? |
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| IgE |
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| What induces degranulation and releases histamine? |
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| Cross-linking or receptor bound IgE by Ag |
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| Which two Immunoglobulins are membrane-bound and co-expressed on mature B cells? |
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| IgD and IgM |
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| T/F Multiple Ab's can recognize the same Ag because there are many different epitopes on a single Ag. |
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| True |
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| What is the Ab response to an Ag which induces a mixture of Abs to one Ag?; What does this result in? |
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| Polyclonal Ab Response; Ab heterogeneity = increases immune protection |
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| What is the Ab response to a single epitope? |
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| Monoclonal Ab (mAb) |
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| T/F; It is feasible to purify monoclonal Ab from polyclonal Ab. |
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| False; it is NOT feasible |
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| What two cells are fused in the preparation of mAbs? |
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| Ab-producing B cell ; plasmacytoma |
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| Describe the Ag-Ab Interaction. |
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| Reversible ; Non-covalent Van der Waals interactions |
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| What is defined as the measure of the strength of the binding ease of association or dissociation? |
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| Affinity |
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| What is defined as an increase in affinity due to multivalent binding or the summation of multiple affinities? |
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| Avidity |
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| What is a substance able to generate antibody or T cell responses? |
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| Immunogen |
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| What are the three most important characteristics of a good antigen? |
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Size: larger is better Chemical Composition: Proteins ; Carbohydrates ; Lipids Similarity to self-antigens: multiple differences are better |
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| What is an important characteristic for T cell Ag response? |
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| Degradability |
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| What is the term for a Non-immunogenic substance, usually low molecular weight, that can induce Ab formation when coupled to a larger "carrier" molecule? |
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| Hapten |
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| Which three Hapten examples can you make monoclonal Ab's to? |
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| Cortisol, Estradiol, & Testosterone |
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| What is the term for Ab's binding Ag's & sticking together? |
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| Agglutination |
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| T/F Antibodies can inhibit attachment of bacteria to cells. |
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| True |
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| What does a bacteria tagged with Ab's bind to on the macrophage cell surface? |
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| Fc receptors |
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| What is the term for any molecule that acts as a binding enhancer for the process of phagocytosis? |
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| Opsonization (via Fc Receptor) |
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| Is it typical to find a peptide on an MHC?; What are the two possibilities for it? |
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| Always has a peptide; usually from self, but if it is a foreign peptide it alerts T cells |
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| What are the four good Ag-Ab reactions In Vivo? |
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| Neutralization, Opsonization, Complement Lysis, ; Prevention of Adherence |
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| What test is used to see if a person has been infected with a virus such as HIV? |
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| Enzyme Linked ImmunoSorbent Assay; (ELISA); first line assay/preliminary test |
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| After an ELISA test is preformed what is done to determine which viral G's the patient has made Ab's to? |
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| Western Blot (second line assay) |
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| Is it possible to have Ab's without being exposed to a particular virus? |
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| Yes, because some viral Ag's are cross-reactive |
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| What is screened for in a pregnancy test? |
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| Human Chorionic Gonadotrophin; prevents Ab's from agglutinating |
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| After Ab binds Ag, the outcome depends on what? What determines effector functions? |
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| Constant region of the heavy chain; Ab isotype |
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| At what level does diversity operate? |
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| lymphocyte level |
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| What causes isotype switching? |
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| Ag binding |
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| Describe the parts found in an original DNA sequence. (as it relates to isotype switching) |
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| Leading Region, Variable Regions, Joining Regions, Constant Regions, and Introns |
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| Describe the parts of an mRNA strand. |
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| Leading region, Variable region, and Constant region (no introns) |
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| What is the process of splicing together segments of genes in order to generate tremendous diversity without monopolizing the genome? |
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| Ig or TCR gene rearrangement |
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| What are the segments found in light chains? |
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| κ and λ light chains each have; Leading, Variable, Joining, and Constant |
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| What are the segments found in heavy chains? |
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| Leading, Variable, Diversity, Joining, and Constant |
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| Describe the mechanism of Immunoglobulin Gene Recombination. |
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| (also called Somatic Recombination) Gene segment forms a loop that is then excised leaving the outer portions adjacent to each other |
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| T/F Cells continue to proliferate between each step in Somatic Recombination resulting in even more possibilities for differentiation. |
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| True |
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| How many possible Ab's can be made?; How many different Ab's are produced by each B cell or plasma cell? |
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| 3 million; only ONE |
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| What regulates Isotype Switching by Somatic Recombination? |
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| cytokines produced by T cells (T cells regulate B cells) |
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| T/F Cells that do not undergo isotype switching may still respond to Ag. |
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| False; only cells that switch will respond to Ag |
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| In what order and what amounts are the immunoglobulins produced in a Primary Response? |
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| IgM followed by IgG in approximately equal quantities |
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| In what order and in what amounts are different isotypes expressed in a secondary response? |
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| IgM and IgG about the same time; much more IgG than IgM (b/c cell remembers how to make IgG) |
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| What is the Ag-binding portion of the T Cell Receptor? |
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| Variable alpha & beta regions |
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| Can TCR exist in secreted form? |
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| No, only as a transmembrane Ag receptor |
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| In what organ do TCR's undergo somatic gene recombination? |
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| Thymus |
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| What are the parts of the gene segment that codes for TCR variable region? |
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| Variable, Joining, Constant |
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| Can B cells recognize intact protein Ag's? What about T cells? |
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| B cells - Yes; T cells - No (must be degraded) |
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| What results in autoreactive B and T cells that are not eliminated? |
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| Autoimmune Disease |
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| What can result from chromosomal translocations arising during VDJ recombination or isotype switching? |
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| Lymphoid Malignancies |
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| What are the major differences between B & T cell Ag Receptors? |
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B cell: Immunoglobulin, B cell Transmembrane protein, plasma secreted effector T cell: TCR, T cell Transmembrane protein, CD4 Th, CD8 Tc |
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| Where are proteins denatured to be presented? What denatures them? |
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| Lysozyme; proteases |
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| T/F B cell antibodies can operate at a distance. |
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| True |
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| Do B cells recognize intact Ag's or bound peptides?; What about T cells? |
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| B cells: Intact Ag's T cells: degraded peptides on MHC |
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| T/F Ag-specific T cell function requires MHC contact, but does not require cell-to-cell interaction. |
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| False; requires MHC and cell-to-cell contact |
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| What cells express MHC Class I? To which cells do they present? |
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| All nucleated cells; CD8 T cells (Cytotoxic killer cells and kills virus infected cells) |
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| What cell have MHC Class II and to what cells do they present? |
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| APC's (dendritic cells, B cells, MQ's); CD4 T cells (T helper cells) |
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| What occurs after T helper cells are activated? |
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| B cells proliferate, differentiate, & isotype switch and help activate MQ's to kill intracellular pathogens |
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| How do CD4 T cells help B cells? |
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| T ; B cell form very close contact and T cell secretes IL-4 into the pocket b/w the cells to induce isotype switching in the B cell |
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| Is it possible for a B cell to express MHC class I and class II? |
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| Yes; if it is presenting an Ag |
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| Describe T cell screening. |
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| T cells go from cell to cell scanning the self-peptides on MHC Class I until it finds an MHC Class II with foreign Ag |
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| Is the peptide binding cleft found on the membrane proximal or distal domain of MHC classes I and II? |
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| Distal |
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| In what portion of the MHC does the peptide sit?; How does it differ between class I and II? |
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| Beta Sheets; MHC class I is surrounded on all sides by the MHC, Class II runs the full lenth of the MHC |
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| How does the structure of MHC differ between classes I and II?; What are the subclasses of each? |
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Class I: 3 ; and 1 ; chain with A, B, ; C types Class II: 2 ; and 2 ; chains with DP, DQ, ; DR types |
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| What is described as allelic variation in MHC genes and is concentrated in the peptide binding regions of Class I and Class II? |
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| MHC Polymorphism |
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| How many MHC genes does each individual inherit? |
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| 9 maternal and 9 paternal |
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| What are the consequences of MHC Polymorphism? |
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| Organ tissue transplants are difficult; change peptide binding specificity of MHC; pathogens could mutate to avoid immune detection by MHC's |
