Quiz 2 Material

Front 1

Describe basic structure of immunoglobulin molecule.

Back 1

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.

Front 2

Describethe enzymatic digestion used to obtain these fragments:(Fc, Fab, F(ab)2.

Back 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.

Front 3

What is Fc, Fab and Fab2?

Back 3

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)

Front 4

Describe the major regions of Ig molecule.

Back 4

1. Antigen-binding = variable.
2. Hinge= links two Fabs. Allows it to bind to epitopes space variable distances
apart.
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.

Front 5

Describe the domain structure of the Ig molecule.

Back 5

Contains characteristic motifs that are 110 aa in length. Within each motif are polypeptide loops of around 40-60aa, linked by intrachain disulfide bonds.

Front 6

Describe char. features of immunoglobulin superfamily.

Back 6

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.

Front 7

Define the nature of determinants recognized by T lymphocytes.

Back 7

MHC 1 = CD8
MHC 2 = CD4
CD1 = related to MHC1. Presents lipids to T cells. (TB and leprosy)

Front 8

List3 types of APC./

Back 8

1. Dendritic cells.
2. Macrophages.
3. B cells
(Note: MHC Class II is on all APCs)

Front 9

Explain how polypeptides are converted to peptide antigens by antigen processing.

Back 9

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.

Front 10

Explain role of coreceptor molecles involved in presentation of Ag to T cells.

Back 10

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.

Front 11

Explain the process by which superantigens activate T cells.

Back 11

Superantigens bind TCR outside of the ag-specific porition with an affinity that is much greater than for normal antigen.

Front 12

Describe molecules involved in B cell activation.

Back 12

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.

Front 13

What 2 signals are required for T cells to b/c activated?

Back 13

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).
Dendritic:T-cell=
B7:CD-28
CD40:CD40L

Front 14

What differentiates a naive from a memory T cell?

Back 14

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).

Front 15

List classes and subclasses of Ig molecules.

Back 15

1. IgG - 4 gamma subclasses.
2. IgA - 2 alpha subclasses.
3. IgM -
4. IgD
5. IgE

Front 16

Explain the difference b/w isotype, allotype & idiotype.

Back 16

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.

Front 17

What regulatory mechanisms control immune response to antigens?

Back 17

1.Central:
*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.

Front 18

Define clonal deletion.

Back 18

Ridding body of self-reacting cells.

Front 19

Define clonal anergy.

Back 19

Cells that react to self can bind antigen, but they don't differentiate into mature B cells or effective T cells.

Front 20

Identify the nature of a tolerogen.

Back 20

Binds cells and eliminate by clonal deletion.

Front 21

Discuss role of co-receptors in regulating immune responses.

Back 21

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.

Front 22

Identify components of the classive, alternative, & membrane complement pathway.

Back 22

Classical:
C1s-C4b-C4bC2-C4b2a-c3b
Alternative:
C3-C3b-C3bB-C3bBb-C3b-(C3b)2Bb-C5-
Membrane Attack Pathway:
C5b +Cb6=C5b6-C5b67-C5b678-Membrane attack complex - c8-c9

Front 23

What is C4b2a?

Back 23

A C3 convertase in the classical pathway.

Front 24

What is C4b2a3b?

Back 24

C5 convertase in classical pathway.

Front 25

What is C3bBb?

Back 25

Alternative pathway C3 convertase.

Front 26

What is (C3b)2Bb

Back 26

Alternative pathway C5 convertase.

Front 27

How is 4 ways complement system is passively regulated?

Back 27

I. Passive
a. Short-lived enzymes
b. Need for cofactors at each step.
c. Enzymes require ions (Mg++, Ca++)
d. Physio pH inhibits activation.

Front 28

How is the complement system actively regulated?

Back 28

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)

Front 29

List 8 biological functions of complement activation (C5a & C5a des Arg).

Back 29

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.

Front 30

Describe the role of complement in chemotaxis.

Back 30

C5a and C5a des Arg act as chemotaxic factor for every cell in immune system when at low concentration.

Front 31

Describe role of complement in anaphylotoxins.

Back 31

C3a and C5a.
Mast cells and basophils have receptors that cause them to release mediators, primarily histamine.

Front 32

Describe role of complement in opsonization.

Back 32

Allows phagocyte recognition.
C4B + C4Bi
C1Q
C3B + C3bi

Front 33

What is Affinity and Avidity?

Back 33

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

Front 34

How does ELISA work?

Back 34

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.

Front 35

Explain flow cytometry.

Back 35

Detects specific cell surface molecules. Ab bind to markers.

Front 36

Explain radioimmunoassay.

Back 36

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

Front 37

Describe the kinetics of a immune response.

Back 37

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.

Front 38

What is a polyclonal antibody?

Back 38

Antibodies produced by many clones of B cells to many epitopes on a single antigen.

Front 39

Describe anatomical location of different Ig classes.

Back 39

IgG -placenta.
IgA - secretions
IgM - secretion
IgD - naive mature B cells
IgE - bound to mast cells.

Front 40

What cellular and molecular components are involved in acute inflammation?

Back 40

cell: neutrophils, endothelial, mast cells, basophils, platelets
Molecular:

Front 41

What role do cell adhesion molecules play in inflammation?

Back 41

Diapedesis.
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.

Front 42

Explain role of endothelial cell activation in leukocyte recruitment.

Back 42

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)

Front 43

What physiologic changes produce local symptoms of inflammation?

Back 43

1. INcreased blood flow (hyperemia)
2. Increased vascular permeability.
3. Diapedesis of WBCs.

Front 44

What are the chemotactic factors involved in recruitment of inflammatory cells?

Back 44

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.

Front 45

Describe the pathway involved in formation of reactive oxygen intermediates.

Back 45

Neutrophils phagocytose pathoens & destroy them by oxygen-indep or oxygen-dep mechanisms.
O2-dependent:
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.

Front 46

What is myeloperoxidase?

Back 46

Converts hydrogen peroxidase and Cl- into HOCL. Responsible for the color of pus. Part of neutrophils oxygen-dependent destruction of pathogens.

Front 47

Catalase is used by?

Back 47

macrophages

Front 48

Glutathione peroxidase is used by?

Back 48

neutrophils.

Front 49

How do neutrophils destroy pathogens in an oxygen-independent way?

Back 49

Release of substances within lysozomal granules. Defensins, Lactoferrin,Acidic pH, degradative enzymes.

Front 50

Describe systemic changes in acute inflammation?

Back 50

1.Fever
2. Leukocytosis
3. Breakdown of muscle via prostaglandin.
4.Lipver protein GRPII increases.
5. Increased sed rate.

Front 51

Characteristics of atopic conditions.

Back 51

Allergy = Type 1.
Immediate onset.
Mediated by IgE and sometimes histamine.

Front 52

How are mast cell degranulated?

Back 52

IgE production. Ab bind to mast cells via Fc epsilon receptor.

Front 53

What do activated mast cells release?

Back 53

IL-4 which stimulates B cell to produce more IgE. IL-4 also stimulates Th2 cells which also release IL-4.

Front 54

List 3 mediators inside the granules of Mast cells.

Back 54

1. Histamine.
2. Lipid mediators which are made from arachidonic acid.

Front 55

What pathologic changes occur in anaphylacsis?

Back 55

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.

Front 56

What is role of eosinophils in allergic & analphylactic reactions?

Back 56

Major source of tissue damage. Mast cell releasesIL-4which attracts eosinophils. E's release cationic granule proteins, including MBP and eosinophil peroxidase.

Front 57

Describe 3 tests used to evaluate atopic conditions.

Back 57

1. Skin test.
2. Immunoassay
3. RAST (detects specific antibody to a specific allergan).