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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
Q

[Special Characteristics]

IgA

A

Majority of secreted Ab in mucosal secretions and in colostrum

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26
Q

[Special Characteristics]

IgE

A

Responds against parasitic worms

Hypersensitivity

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27
Q

[Special Characteristics]

IgD

A

No biological effector yet

Together with IgM is the major membrane bound Ig expressed by mature B-Cells

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28
Q

Where is IgA most abundant?

A

External secretions such as breast milk, saliva, tears, mucosa and digestive tract

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29
Q

Where is IgE mostly found? What is it associated with?

A

Highly potent despite low concentrations
Found on skin and mucosa
Associated with mast cells

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30
Q

Define: Epitope

A

Antigen determinant; part that is actually recognized by the immune system

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31
Q

Define: Paratope

A

Part of antibody in contact with antigen/binds with epitope

32
Q

Are antigen-antibody interactions covalent or non-covalent?

A

Non-covalent

33
Q

Three Pathways of the Complement System

A
  1. Classical
  2. Alternative
  3. Mannose-Binding Lectin Pathway
34
Q

Final reaction of all pathways lead to formation of?

A

Membrane Attack Complex

35
Q

Function: Membrane Attack Complex

A

Leads to entry of water, ions, and small molecules to disrupt the osmotic balance of the cell

36
Q

Define: Classical Pathway

A

Activated by immune complexes of IgM and some subtypes of IgG

37
Q

Define: Alternative Pathway

A

Activated by cell-surface constituents foreign to the host and also by the classical pathway

38
Q

Define: Mannose-Binding Lectin Pathway

A

Activated by mannose-bearing foreign substances (Most bacteria)

39
Q

Functions of Complement Pathways (4)

A
  1. Lysis of cells, bacteria, and virus
  2. Opsonization
  3. Inflammatory Response
  4. Clearance of Immune Complexes
40
Q

How can a human make more antibodies with different specifications than there are genes in its genome?

A

Minor Source

Major Source

41
Q

Define: Minor Source

A

Multiple variant genes in the germline DNA sequence codes for natural antibodies (IgM are produced even without antigen exposure)

42
Q

Define: Major Source

A

Modification of germline DNA sequence to yield multiple variant antibody genes for both heavy and light chains

43
Q

What are some other ways to increases antibody specification?

A

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
Q

Anatomic Barriers (2)

A

Skin

Mucous Membrane

45
Q

pH of Skin?

A

3-5

46
Q

Physiologic Barriers (3)

A

Temperature
Low pH
Chemical Mediators

47
Q

Define: Toll-like receptors (TLRs)

A

Membrane-bound receptors that recognize commonly encountered pathogen-associated molecular patterns (PAMPs) leading to secretion of cytokines and chemokines

48
Q

TLR3 recognize?

A

Double-stranded RNA (common in viral genomic material)

49
Q

TLR4 recognize?

A

LPS or Lipopolysaccharides (Wall component of G- Bacteria)

50
Q

Define: Cytokines

A

Non-antibody molecule that regulate immune function as either a paracrine or autocrine signal

51
Q

Function: Interferon

A

Secreted by infected cells to induce antiviral state in neighboring cells

52
Q

Function: Chemokines

A

Specialized cytokines which attract leukocytes and promote their adhesion to endothelium

53
Q

Define: Opsonization

A

Deposition of opsonin on an antigen to allow stable adhesive contact with a phagocytic cell

54
Q

Cardinal Signs of Inflammation (5)

A
  1. Tumor (Swelling)
  2. Rubor (Redness)
  3. Calor (Heat)
  4. Dolor (Pain)
  5. Loss of Function
55
Q

What Ig predominates in first infection?

Second infection?

A

IgM

IgG

56
Q

What activates B cells? What stimulates it?

A

Antigens

T-Helper Cells

57
Q

What are mature B cells called?

A

Plasma Cells

58
Q

Two Classifications of Antigens for B-Cell Activation

A
  1. Thymus-Independent Antigen

2. Thymus-Dependent

59
Q

Define: Thymus-Independent Antigen

A

Activate B cells without helper T-Cells

Only IgM produced, no immunologic memory

60
Q

Types of Thymus-Independent Antigens

Function

A

 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
Q

[TI-1 Antigen Activation]

How does activation occur?

A

Signal 1 produced when BCR recognizes nitrogen

Signal 2 provided when LPS is recognized by TLR4

62
Q

Define: Thymus-Dependent Antigen

A 
Activates B cells with helper T-cells
Typically induce response with class switching, affinity maturation, and generation of memory B-cells
63
Q

Define: Antibody-dependent Cell-mediated Cytotoxicity

A

Mediated by non-specific cells with Fc receptors as NK cells and Monocytes

64
Q

Define: Antibody-dependent Enhancement of Infection

A

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
Q

How do T-Cells recognize Antigens?

A

Fab-like TCell Receptor

66
Q

[Cytotoxic T Cells vs Helper T Cells]

What do Tc express?
Th?

A

Tc: CD8+
Th: CD4+

67
Q

[Cytotoxic T Cells vs Helper T Cells]

What MHC Class do each recognize?

A

Tc: MHC I
Th: MHC II

68
Q

How do Tc cellls kill?

A

Apoptosis through perforins and granzymes

69
Q

Function: Th 1

A

Secrete cytokines that stimulate cell-mediated killing by Tc and Macrophages

70
Q

Function: Th2

A

Secrete cytokines that stimulate IgE antibody production

71
Q

Function: Th17

A

Secretes IL-17

Recruits neutrophils and macrophages

72
Q

Dysfunction of what helper T cell cause autoimmune inflammatory disorders?

A

Th17 dysregulation

73
Q

Regulatory Cells are also called?

What do they express?

A

Treg Cells/Tregs

Foxp3

74
Q

What are the major Antigen Presenting Cells in the body? (3)

A

Dendritic Cells
Macrophages
B Lymphocytes

75
Q

How does Endogenous Antigen Processing work?

A

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
Q

Difference of Class II and Class I MHC Molecules vis a vis presentation of antigens?

A

MHC I: Endogenous Protein Antigens

MHC 2: Exogenous Protein Antigens

77
Q

Differentiate Active Immunization vs. Passive Immunization

Which produces immunological memory?

A

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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