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[OS 201] 4th Lecture Exam > Basic Concepts in Immunology > Flashcards

Basic Concepts in Immunology Flashcards

1
Q

Ratio of Human:Non-Human Cells

A

1:10

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2
Q

% Dry Weight of Feces Composed by Microorganisms

A

20%

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3
Q

Define: Danger Hypothesis/Model/Theory

A

o Core function of immune system: perceive danger (rather than recognition of self/non-self)
o Immune responses: directed against perceived danger (danger signals that suggest cellular/tissue damage or invasion by pathogen)

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4
Q

Define: Danger-Signal Threshold

A

If a danger signal rises above the threshold, it will cause an immune response

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5
Q

Define: Tolerance

A

Unresponsiveness to self/non-self molecules

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6
Q

Define: Immunity

A

Resistance to harmful effects of disease-causing agents

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7
Q

Define: Hypersensitivity

A

Pathologically exaggerated immune reactions with infalmmation

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8
Q

Define: Hygiene Hypothesis

A

Insufficient exposure of host to pathogens of natural environment during development = increased risk of autoimmunity and allergy

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9
Q

Why are C-Section babies more prone to diseases

A

Not exposed to microorganisms in the vaginal tract, have lower thresholds and more susceptible to allergies

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10
Q

Define: Old Friends Hypothesis

A

o Old friends of host: organisms very closely
associated with the host during evolution
 Microbes and helminths living as saprophytes/commensals/ parasites
o Us AND them, not us against them
o Old friends train immune system to self-regulate against hypersensitivity

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11
Q

Define: Hygiene Hypothesis vis-a-vis Danger Hypothesis

A

Threshold for perception of danger may be really low because of insufficient exposure to “old friends”

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12
Q

Differentiate: Humoral and Cellular Immunity

A

H: Mediated by soluble substances in body fluids (protein in plasma, seru)

C: Mediated by living cells (e.g. phagocytes)

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13
Q

[T/F]

All immunity has a cellular basis

A

T

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14
Q

What is the first line of dense?

A

Innate immunity, present even in primitive organisms

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15
Q

Define: Antigen

A

Substance with potential to be recognized by the immune system

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16
Q

Define: Antobidy

A

Secreted form of immunoglobin that can mediate recognition of antigen

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17
Q

Define: Antibody Structure

A

Y-Shaped molecule with 2 arms and 1 trunk

4 polypeptide chains: 2 heavy and 2 light chains linked by disulfide bond

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18
Q

What is the secondary structure of an antibody?

A

Anti-parallel beta-pleated sheets

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19
Q

Define: Fo Region of Antibody

A

Fragment that can be recrystallized

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20
Q

What determines the Antibody class?

A

Constant region of heavy chain

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21
Q

What is responsible for differing binding specificity of antibodies?

A

Variable Region of heavy and light chains

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22
Q

What are the monomeric antibody classes?
What are the dimeric classes?
What are the pentameric classes?

A

M: IgG, IgD, IgE
D: IgA
P: IgM

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23
Q

[Special Characteristics]

IgM

A

1st to appear during exposure

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24
Q

[Special Characteristics]

IgG

A

Majority of antibodies

Can cross placental barrier

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25
[Special Characteristics] IgA
Majority of secreted Ab in mucosal secretions and in colostrum
26
[Special Characteristics] IgE
Responds against parasitic worms | Hypersensitivity
27
[Special Characteristics] IgD
No biological effector yet | Together with IgM is the major membrane bound Ig expressed by mature B-Cells
28
Where is IgA most abundant?
External secretions such as breast milk, saliva, tears, mucosa and digestive tract
29
Where is IgE mostly found? What is it associated with?
Highly potent despite low concentrations Found on skin and mucosa Associated with mast cells
30
Define: Epitope
Antigen determinant; part that is actually recognized by the immune system
31
Define: Paratope
Part of antibody in contact with antigen/binds with epitope
32
Are antigen-antibody interactions covalent or non-covalent?
Non-covalent
33
Three Pathways of the Complement System
1. Classical 2. Alternative 3. Mannose-Binding Lectin Pathway
34
Final reaction of all pathways lead to formation of?
Membrane Attack Complex
35
Function: Membrane Attack Complex
Leads to entry of water, ions, and small molecules to disrupt the osmotic balance of the cell
36
Define: Classical Pathway
Activated by immune complexes of IgM and some subtypes of IgG
37
Define: Alternative Pathway
Activated by cell-surface constituents foreign to the host and also by the classical pathway
38
Define: Mannose-Binding Lectin Pathway
Activated by mannose-bearing foreign substances (Most bacteria)
39
Functions of Complement Pathways (4)
1. Lysis of cells, bacteria, and virus 2. Opsonization 3. Inflammatory Response 4. Clearance of Immune Complexes
40
How can a human make more antibodies with different specifications than there are genes in its genome?
Minor Source | Major Source
41
Define: Minor Source
Multiple variant genes in the germline DNA sequence codes for natural antibodies (IgM are produced even without antigen exposure)
42
Define: Major Source
Modification of germline DNA sequence to yield multiple variant antibody genes for both heavy and light chains
43
What are some other ways to increases antibody specification?
o Addition of bases (palindromic nucleotides and N nucleotides) o Junctional diversification during gene segment joining o Combinational joining of light and heavy chains (“mix and match” different segments) o Somatic hypermutation (substitution of bases)
44
Anatomic Barriers (2)
Skin | Mucous Membrane
45
pH of Skin?
3-5
46
Physiologic Barriers (3)
Temperature Low pH Chemical Mediators
47
Define: Toll-like receptors (TLRs)
Membrane-bound receptors that recognize commonly encountered pathogen-associated molecular patterns (PAMPs) leading to secretion of cytokines and chemokines
48
TLR3 recognize?
Double-stranded RNA (common in viral genomic material)
49
TLR4 recognize?
LPS or Lipopolysaccharides (Wall component of G- Bacteria)
50
Define: Cytokines
Non-antibody molecule that regulate immune function as either a paracrine or autocrine signal
51
Function: Interferon
Secreted by infected cells to induce antiviral state in neighboring cells
52
Function: Chemokines
Specialized cytokines which attract leukocytes and promote their adhesion to endothelium
53
Define: Opsonization
Deposition of opsonin on an antigen to allow stable adhesive contact with a phagocytic cell
54
Cardinal Signs of Inflammation (5)
1. Tumor (Swelling) 2. Rubor (Redness) 3. Calor (Heat) 4. Dolor (Pain) 5. Loss of Function
55
What Ig predominates in first infection? | Second infection?
IgM | IgG
56
What activates B cells? What stimulates it?
Antigens | T-Helper Cells
57
What are mature B cells called?
Plasma Cells
58
Two Classifications of Antigens for B-Cell Activation
1. Thymus-Independent Antigen | 2. Thymus-Dependent
59
Define: Thymus-Independent Antigen
Activate B cells without helper T-Cells | Only IgM produced, no immunologic memory
60
Types of Thymus-Independent Antigens | Function
 TI-1: typically polyclonal B-cell activators; mitogens that non-selectively induce proliferation of B cells (e.g. LPS)  TI-2: highly repetitious molecules (e.g. polymeric proteins, polysaccharides); selectively activate mature B cells bearing antigen-specific BCR; activate mature B cells thru extensive cross- linking of BCRs by antigen
61
[TI-1 Antigen Activation] How does activation occur?
Signal 1 produced when BCR recognizes nitrogen | Signal 2 provided when LPS is recognized by TLR4
62
Define: Thymus-Dependent Antigen
``` Activates B cells with helper T-cells Typically induce response with class switching, affinity maturation, and generation of memory B-cells ```
63
Define: Antibody-dependent Cell-mediated Cytotoxicity
Mediated by non-specific cells with Fc receptors as NK cells and Monocytes
64
Define: Antibody-dependent Enhancement of Infection
Antibodies may enhance infections by having low affinity and only partially coating the virus. This leads to its facilitated entry into cells since it is not neutralized.
65
How do T-Cells recognize Antigens?
Fab-like TCell Receptor
66
[Cytotoxic T Cells vs Helper T Cells] What do Tc express? Th?
Tc: CD8+ Th: CD4+
67
[Cytotoxic T Cells vs Helper T Cells] What MHC Class do each recognize?
Tc: MHC I Th: MHC II
68
How do Tc cellls kill?
Apoptosis through perforins and granzymes
69
Function: Th 1
Secrete cytokines that stimulate cell-mediated killing by Tc and Macrophages
70
Function: Th2
Secrete cytokines that stimulate IgE antibody production
71
Function: Th17
Secretes IL-17 | Recruits neutrophils and macrophages
72
Dysfunction of what helper T cell cause autoimmune inflammatory disorders?
Th17 dysregulation
73
Regulatory Cells are also called? | What do they express?
Treg Cells/Tregs | Foxp3
74
What are the major Antigen Presenting Cells in the body? (3)
Dendritic Cells Macrophages B Lymphocytes
75
How does Endogenous Antigen Processing work?
Endogenous antigens are degraded into peptides by proteasomes and assemble with MHC I molecules in the rough ER before being presented on the membrane surface
76
Difference of Class II and Class I MHC Molecules vis a vis presentation of antigens?
MHC I: Endogenous Protein Antigens | MHC 2: Exogenous Protein Antigens
77
Differentiate Active Immunization vs. Passive Immunization Which produces immunological memory?
A: Exposure to antigen eliciting endogenous immune response P: Transfer of pre-formed immune factors from an exogenous source (antibody transfer) Active produces memory but passive immunization has a faster response onset

[OS 201] 4th Lecture Exam (5 decks)

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