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57 Cards in this Set

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  • Back
Describe basic structure of immunoglobulin molecule.
2 H chains, 2 L chains.
Disulfide bonds link L to H and H to H.
NH3 is at variable ends. COO- at constant end.
Describethe enzymatic digestion used to obtain these fragments:(Fc, Fab, F(ab)2.
Papain: cleaves Ig in hinge region- results in 3 pieces (2 Fab and 1 Fc)

Pepsin: cleaves below disulfide bond and creates Fab2 + Fc region which is digested into fragments.
What is Fc, Fab and Fab2?
Fc = constant region of heavy chain only.

Fab = light chain (V and C) + heavy chain V1 and C1 only.

Fab2 = contains both antigen binding sites. Light chain + heavy chain (V1 and C1) bound by disulfide bonds. (Pepsin)
Describe the major regions of Ig molecule.
1. Antigen-binding = variable.
2. Hinge= links two Fabs. Allows it to bind to epitopes space variable distances
3. Hypervariable or Complementarity-determining region (CDR): Areas within variable regions (L&H) sequences where it varies more than others. 3 for H chain, 3 for L chain with framework regions in between.
4. Antigen binding site = 1 variable L + 1 variable H.
5. Fc = constant regions; where biological activity is generated.
Describe the domain structure of the Ig molecule.
Contains characteristic motifs that are 110 aa in length. Within each motif are polypeptide loops of around 40-60aa, linked by intrachain disulfide bonds.
Describe char. features of immunoglobulin superfamily.
Immunoglobulins are glycoproteins in the immunoglobulin superfamily that function as antibodies.
Have recognition functions.
Char by Ig Domain.
Have primary sequences that are homologous to Ig domains.
Define the nature of determinants recognized by T lymphocytes.
MHC 1 = CD8
MHC 2 = CD4
CD1 = related to MHC1. Presents lipids to T cells. (TB and leprosy)
List3 types of APC./
1. Dendritic cells.
2. Macrophages.
3. B cells
(Note: MHC Class II is on all APCs)
Explain how polypeptides are converted to peptide antigens by antigen processing.
Extracellular ag:All APCs can internalize antigens, ag fuses with lysosome and is digested by acidic environment. Presented to CD4.

Intracellular Ag: Proteases break down the virus for presentation to CD8.
Explain role of coreceptor molecles involved in presentation of Ag to T cells.
1. CD4 stabilizes the interaction b/w MHCII and TCR by binding to MHC outside the Ag-binding area. AND CD4 sends signalto T cell to begin activation.

2. CD3 also is required.
Explain the process by which superantigens activate T cells.
Superantigens bind TCR outside of the ag-specific porition with an affinity that is much greater than for normal antigen.
Describe molecules involved in B cell activation.
1. CD40 stimulates B cell prolif & diff.
2. LFA-2 on B cell binds with CD2 on T cell to stabilize interaction.
3. ICAM on B cell:LFA-1 on T cell to stabilize interaction.
4. T cells secrete cytokines that stimulate B-cell affinity maturation & isotype switching.
What 2 signals are required for T cells to b/c activated?
There is evidence of a critical role for two distinct costimulator molecules on T cells which interact with specific ligands on the surface of antigen presenting cells (APC).
What differentiates a naive from a memory T cell?
Effector TH cells secrete cytokines, proteins or peptides that stimulate or interact with other leukocytes, including the TH cells themselves. Proliferating helper T cells that develop into effector T cells differentiate into two major subtypes of cells known as TH1 and TH2 cells

Memory TH cells retain the TcR affinity of the originally activated T cell, and are used to act as later effector cells during a second immune response (e.g. if there is re-infection of the host at a later stage).
List classes and subclasses of Ig molecules.
1. IgG - 4 gamma subclasses.
2. IgA - 2 alpha subclasses.
3. IgM -
4. IgD
5. IgE
Explain the difference b/w isotype, allotype & idiotype.
Isotype = differences in Ig due to diff in constant regions of heavy & light chains.

Allotype = differences in Fc region as result of minor genetic differences (no effect on function; applies to IgG and IgA only).

Idiotype = differ in variable regions. Difers from one clone to another.
What regulatory mechanisms control immune response to antigens?
*B-cells that recognize self are eliminated.
*T-cells that recognize self strongly are eliminated.
2. Peripheral:
* Immunological enhancement - one form of immune response blocks expression of another. (IgG mops up all Ag, so IgA not needed).
* Immunological paralysis- nonbiodegradable Ag is taken up, released in whole, taken up again, etc.
* Anti-Idiotypic Ab - blocks original Ab and blocks its appearance.
* Immunologically-privileged sites - anterior chamber of eye and testes. These sites eliminate lymphocytes.
Define clonal deletion.
Ridding body of self-reacting cells.
Define clonal anergy.
Cells that react to self can bind antigen, but they don't differentiate into mature B cells or effective T cells.
Identify the nature of a tolerogen.
Binds cells and eliminate by clonal deletion.
Discuss role of co-receptors in regulating immune responses.
2 forms of CD4 T-regulatory cells with CD25 on surface. Naturally occuring (inhibit other T cells through cell contact) and
Adaptive T-regs (Convert T cells into T-regs that release Il-10 or TGF-beta that control activation of auto-aggressive T cells.
Must have CD25+: if not, autoimmunity to organs develops.
Identify components of the classive, alternative, & membrane complement pathway.
Membrane Attack Pathway:
C5b +Cb6=C5b6-C5b67-C5b678-Membrane attack complex - c8-c9
What is C4b2a?
A C3 convertase in the classical pathway.
What is C4b2a3b?
C5 convertase in classical pathway.
What is C3bBb?
Alternative pathway C3 convertase.
What is (C3b)2Bb
Alternative pathway C5 convertase.
How is 4 ways complement system is passively regulated?
I. Passive
a. Short-lived enzymes
b. Need for cofactors at each step.
c. Enzymes require ions (Mg++, Ca++)
d. Physio pH inhibits activation.
How is the complement system actively regulated?
a. plasma protein inhibitors at every step.(C1 inhibitor, Factors H & I, C4b binding inhibitor)

b.Cells are coated with major cell surface inhibitory regulators (CR1,MCP,DAF,HRF,MIRL)
List 8 biological functions of complement activation (C5a & C5a des Arg).
1. Opsonin.(C4B,C1Q,C3B)
2. Anaphylatoxin (C3a,C5a)
3. Chemotaxis Factor(
4. Expression/Activation of Adhesion molecules.
5. Activation of Phagocyte Anti-Microbial funtion.
6. Cytokine production (IL-1,TNF-alpha, IL-6,IL-8)
7. Clearance of soluble immune complexes.
8. Molecular adjuvant to enhance antibody production.
Describe the role of complement in chemotaxis.
C5a and C5a des Arg act as chemotaxic factor for every cell in immune system when at low concentration.
Describe role of complement in anaphylotoxins.
C3a and C5a.
Mast cells and basophils have receptors that cause them to release mediators, primarily histamine.
Describe role of complement in opsonization.
Allows phagocyte recognition.
C4B + C4Bi
C3B + C3bi
What is Affinity and Avidity?
Affinity refers to the strength of binding between a single antigenic determinant and an individual antibody combining site whereas avidity refers to the overall strength of binding between multivalent antigens and antibodies. Avidity is influenced by both the valence of the antibody and the valence of the antigen
How does ELISA work?
Uses an enzyme linked to an antibody or antigen.3 types.
1. Direct: Antigen attached to well. Ab+enzyme added. Substrate added & produces florescence.
2. Indirect- Same as above, except that 1st antibody, then 2nd antibody, then substrate. Used to detect specific antibody.
3. Sandwich - Ab on plate. Then Ag, 2nd Ab, substrate. Used to detect antigen.
Explain flow cytometry.
Detects specific cell surface molecules. Ab bind to markers.
Explain radioimmunoassay.
A highly sensitive and specific assay method that uses the competition between radiolabeled and unlabeled substances in an antigen-antibody reaction to determine the concentration of the unlabeled substance; it can be used to determine antibody concentrations or to determine the concentration of any substance against which specific antibody can be produced
Describe the kinetics of a immune response.
1. Innate.
a. Complement within sec to min.
b. Cellular (neurophils) within 2-3 hrs,peak 5-6 hrs.

2. Adaptive
a. Primary response - IgM 10-12 days after exposure.
b. Secondary - IgG 6-7 days with greater response.
What is a polyclonal antibody?
Antibodies produced by many clones of B cells to many epitopes on a single antigen.
Describe anatomical location of different Ig classes.
IgG -placenta.
IgA - secretions
IgM - secretion
IgD - naive mature B cells
IgE - bound to mast cells.
What cellular and molecular components are involved in acute inflammation?
cell: neutrophils, endothelial, mast cells, basophils, platelets
What role do cell adhesion molecules play in inflammation?
1. Selectins - mediate initial capture & rolling of leukocytes.
2. Ig Superfamily (CD3,CD4,CD8) - ICAM-1 &VCAM-2 serve as receptorsfor adhesion.
3. Integrins (CD11a/CD18) - bind cells to extracellular matrix.
Explain role of endothelial cell activation in leukocyte recruitment.
P-selectin in released from Weibel-Palade bodies of endothelial cells.

Sustained reaction:
Macrophage release IL-1 & TNF-alpha which act on endothelial cells and cause them to synthesize E-selection (loose tethering) and ICAM-1, VCAM-1 (tight adhesion)
What physiologic changes produce local symptoms of inflammation?
1. INcreased blood flow (hyperemia)
2. Increased vascular permeability.
3. Diapedesis of WBCs.
What are the chemotactic factors involved in recruitment of inflammatory cells?
1. Formyl-methionine bacterial peptide.
2. Complement C5a & C5a des arg
3. Leukotriene B4 produced by neutrophils.
4. Platelet-activating Factor
5. Chemokines induced by IL-1, TNF-alpha,LPS, mitogens.
Describe the pathway involved in formation of reactive oxygen intermediates.
Neutrophils phagocytose pathoens & destroy them by oxygen-indep or oxygen-dep mechanisms.
oxy + NADPH (via NADPH oxidase) =superoxide + hydrogen

Superoxideconverted to hydrogen peroxide via superoxide dismutase.

Hydrogen peroxide is converted to water via catalase in macrophases, via glutathione peroxidase in neutrophils.
What is myeloperoxidase?
Converts hydrogen peroxidase and Cl- into HOCL. Responsible for the color of pus. Part of neutrophils oxygen-dependent destruction of pathogens.
Catalase is used by?
Glutathione peroxidase is used by?
How do neutrophils destroy pathogens in an oxygen-independent way?
Release of substances within lysozomal granules. Defensins, Lactoferrin,Acidic pH, degradative enzymes.
Describe systemic changes in acute inflammation?
2. Leukocytosis
3. Breakdown of muscle via prostaglandin.
4.Lipver protein GRPII increases.
5. Increased sed rate.
Characteristics of atopic conditions.
Allergy = Type 1.
Immediate onset.
Mediated by IgE and sometimes histamine.
How are mast cell degranulated?
IgE production. Ab bind to mast cells via Fc epsilon receptor.
What do activated mast cells release?
IL-4 which stimulates B cell to produce more IgE. IL-4 also stimulates Th2 cells which also release IL-4.
List 3 mediators inside the granules of Mast cells.
1. Histamine.
2. Lipid mediators which are made from arachidonic acid.
What pathologic changes occur in anaphylacsis?
Increased mucous secretion and increased bronchial smooth muscle tone, as well as airway edema, contribute to the respiratory symptoms observed in anaphylaxis. Cardiovascular effects result from decreased vascular tone and capillary leakage. Histamine release in skin causes urticarial skin lesions.
What is role of eosinophils in allergic & analphylactic reactions?
Major source of tissue damage. Mast cell releasesIL-4which attracts eosinophils. E's release cationic granule proteins, including MBP and eosinophil peroxidase.
Describe 3 tests used to evaluate atopic conditions.
1. Skin test.
2. Immunoassay
3. RAST (detects specific antibody to a specific allergan).