Lecture 4: Adaptive Immunity Flashcards

1
Q

Hematopoietic stem cell

A

stem cell for all immune cells

produced in the bone marrow

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2
Q

These two cells are derived from hematopoietic stem cell

A

Myeloid Progenitor cell and Lymphoid Progenitor cell

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3
Q

What cell types are produced by the Myeloid Progenitor cell?

A
  • RBC
  • Platelet
  • Neutrophil
  • Eosinophil
  • Basophil
  • Monocyte- produce dendritic cell and macrophage
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4
Q

Monocyte can be further subdivided into:

A

Dendritic cell and Macrophage

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5
Q

Myeloid Progenitor cell produces cell types that are linked to what type of immunity?

A

Innate immunity

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6
Q

What are the cells produced by myeloid progenitor cell that are responsible for inflammation in innate immunity?

A
  • Neutrophil
  • Eosinophil
  • Basophil
  • Monocyte- dendritic cell and macrophage
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7
Q

Cell types produced by Lymphoid Progenitor cell

A
  • Natural Killer cell
  • T Lymphocytes
  • B Lymphocyte
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8
Q

What cell type is produced by the Lymphoid Progenitor cell that plays a role in innate immunity?

A

Natural killer cell

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9
Q

What are the two cell types produced by the Lymphoid Progenitor cell that plays a role in adaptive immunity?

A

T Lymphocytes and B Lymphocyte

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10
Q

Examples of T Lymphocytes

A
  • Helper cells
  • Regulatory cells
  • Cytotoxic cells
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11
Q

B Lymphocyte can further specialize into ________ cell which then generate ________

A

Plasma, Antibodies

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12
Q

Adaptive Immunity

A

Immune response mediated by B and T lymphocytes (B cell/T cell) to infectious agents and noninfectious molecules.

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13
Q

Difference of innate and adaptive immune response when it comes to detection?

A

Innate immunity- detects common microbial structures

Adaptive immunity- Detects vast repertoire of specific molecules on the pathogen

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14
Q

Difference of innate and adaptive immunity in terms of receptors?

A

Innate immunity- receptors are encoded in the germline. No recombination that occurs in the genome to create receptors.

Adaptive immunity- receptors generated by somatic recombination.

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15
Q

Difference of innate and adaptive immunity in terms of repeat exposure

A

Innate immunity- same magnitude of response upon repeat exposure.

Adaptive immunity- Improved “adapted” response to repeat exposure.

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16
Q

Adaptive immune responses are generated in response to “________”

A

Antigens

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17
Q

Antigen (Ag)

A

A “foreign” molecule, typically from a pathogen. Usually it’s foreign, but there are some that are not.

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18
Q

B cells recognize broad types of antigens. What are these antigens?

A
  1. Proteins
  2. Lipopolysaccharides
  3. Lipids
  4. Nucleic acids
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19
Q

T cells are highly specific when recognizing different types of antigens. What are the types of antigens recognized by T cells?

A

peptides (long peptides) derived from proteins

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20
Q

What are the critical mediators of the adaptive immune response?

A

B cells and T cells

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21
Q

Antigen presenting cells (APC)

A

T cells require antigen presentation by dedicated antigen presenting cells.

T cells don’t recognize antigen directly without some form of presentation.

Presents the antigen to the T cell receptor (TCR) of a T cell

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22
Q

How does the B cell detect antigen?

A

B Cell receptor (BCR) directly recognizes its cognate antigen.

B cells directly recognize the antigen through its BCR.

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23
Q

Two forms of adaptive immunity

A
  1. Humoral Immunity
  2. Cellular Immunity
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24
Q

Humoral Immunity

A
  • directed against extracellular microbes.
  • mediated by B lymphocytes
  • B lymphocytes secrete antibodies that NEUTRALIZE and ELIMINATE microbes and microbial toxins.
  • production and secretion of antibodies.
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25
Q

What happens in humoral immunity?

A
  1. Microbe binds to the B cell receptor (BCR) of the B cell.
  2. B cell gets activated
  3. Production of antibodies
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26
Q

Cellular Immunity

A
  • directed against intracellular microbes.
  • mediated by T lymphocytes
  • T lymphocytes activate phagocytes and lymphocytes or kill infected host cells.
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27
Q

What happens in cellular immunity?

A
  1. T lymphocyte (T cell) receptor binds to the receptor of a host cell. Host cell has intracellular microbes
  2. T lymphocytes activate phagocytes and lymphocytes or kill infected host cells.
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28
Q

Why is it not enough to just rely on antibodies?

A

It’s not enough because some microbes might get inside the cells and not be found by antibodies.

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29
Q

Purpose of Humoral and Cellular immune responses in the adaptive immune system

A

Humoral and Cellular immune responses are distinct arms of the adaptive immune system to neutralize microbes in different locations.

30
Q

What is the microbe involved in humoral immunity?

A

extracellular microbes

31
Q

What are the responding lymphocytes in humoral immunity?

A

B lymphocyte

32
Q

Effector mechanism of humoral immunity

A

secreted antibody

33
Q

Functions of humoral immunity

A

Block infections and eliminate extracellular microbes

34
Q

Two types of microbe involved cellular immunity

A
  • Phagocytosed microbes in macrophage
  • Intracellular microbe s(e.g. viruses) replicating within infected cell
35
Q

In cellular immunity, what is the responding lymphocyte if the microbe is phagocytosed microbes in macrophage?

A

Helper T lymphocyte

36
Q

Helper T lymphocyte

A

will further activate the APC to better destroy the ingested microbe.

37
Q

Function of helper T lymphocyte in cellular immunity

A

Activate macrophages to kill phagocytosed microbes

38
Q

In cellular immunity, what is the responding lymphocyte if the microbe involved is intracellular microbes (e.g. viruses)?

A

Cytolytic T lymphocyte

39
Q

Function of cytolytic T lymphocyte in cellular immunity

A

Kill infected cells and reservoirs of infection.

40
Q

Aside from blocking infections, what else do antibodies do?

A

Antibodies will facilitate the ingestion and destruction of a microbe.

41
Q

5 Phases of the immune response

A
  1. Recognition
  2. Activation
  3. Effector phase
  4. Decline
  5. Memory
42
Q

Recognition

A
  • 1st phase of the immune response
  • naive lymphocytes recognize corresponding antigen
43
Q

Activation

A
  • 2nd phase of the immune response
  • lymphocytes differentiate and start clonal expansion (proliferation)
44
Q

Activation, a phase in immune response, requires two signals. What are these?

A
  1. Antigen receptor binds antigen
  2. Microbial or innate immune signals are also required for lymphocyte activation
45
Q

Why does each BCR recognizes a limited number of antigens?

A

Because they have specificity

46
Q

We have millions of B cells, each with its own unique ______

A

BCR

47
Q

Explain clonal expansion

A

When a BCR or TCR detects antigen the B cell or T cell undergoes multiple rounds of cell division, thereby expanding.
Each daughter is identical to the parent cell, i.e. a clone

48
Q

Effector phase

A
  • 3rd phase of immune response
  • differentiated lymphocytes initiate microbial elimination.
49
Q

Decline

A
  • 4th phase of immune response
  • after microbial elimination the signal for lymphocyte activation disappears. Most of the cells activated by antigen die by a process of programmed cell death (apoptosis).
50
Q

What is the main reason for declining? (immune response phase)

A

The stimulating antigen is diminishing in numbers.

51
Q

Why do cells go into apoptosis?

A

They’re not needed anymore

52
Q

Memory

A
  • 5th phase of immune response
  • The remaining cells are memory lymphocytes, which may survive for months or years.
53
Q

The memory cells (adaptive memory) are not like naive cells (innate immunity) because:

A

memory cells react faster.

They are also stronger, better, and faster.

54
Q

What happens in the memory phase of immune response?

A

Prior exposure to one antigen results in stronger responses to subsequent challenges with the same antigen.

55
Q

Each B cell expresses a unique B cell receptor (BCR), which recognizes a distinct ___________________

A

microbial 3-dimensional structure

56
Q

In a B cell that has never previously encountered its target structure (naive B cell), where is the BCR restricted to?

A

The BCR is restricted to the plasma membrane of the B cell.

57
Q

What happens during naive B cells activation?

A
  1. Naive B cells are activated by antigens and other “second” signals.
  2. B cell activation results in their proliferation (clonal expansion) and differentiation into effector cells that actively secrete antibodies.
  3. BCR production is now modified in such a way that the BCR is secreted as an antibody.
58
Q

What is the source for Antibody, a secreted BCR

A

B cells

59
Q

Antibodies secreted by BCR are released into the _________ and __________ fluids by B cells upon infection

A

circulation and mucosal

60
Q

Functions of antibodies released by B cells

A
  • neutralizes microbes and microbial toxins . Microbes will also produce toxins
  • stops microbes from gaining access to or colonizing host cells.
  • does not have access to intracellular microbes
61
Q

T lymphocytes (T cells)

A

T cells also respond to antigens, but require antigen presentation by antigen presenting cells (APC)

62
Q

Where does antigen presenting cells (APC) reside and their function?

A
  • APCs reside in potential sites of microbe entry (skin, G.I. tract, respiratory tract, etc.)
  • APCs capture, process and present antigens to T lymphocytes in peripheral lymphoid tissues.
63
Q

Each T cell expresses a unique ______________

A

T cell receptor (TCR)

64
Q

A single TCR recognizes

A

a single presented antigen

65
Q

What do T cells require to assist antigen recognition?

A

co-receptors

66
Q

Two major subsets of T lymphocytes

A
  1. CD4+ helper T cells
  2. CD8+ cytolytic T cells
67
Q

CD4+ helper T cells

A
  • detect antigens presented by professional antigen presenting cells
  • secrete cytokines to activate other components of the immune response (macrophages, B cells, etc.)
68
Q

CD8+ cytolytic T cells

A
  • detect microbial antigens presented by all nucleated cells and destroy the presenting cell.
69
Q

How do you bring the right lymphocyte together with its cognate antigen upon infection quickly enough to activate the appropriate immune reply?

A

The peripheral lymphoid organs (lymph nodes, spleen, mucosal and cutaneous lymphoid tissues) concentrate antigens and lymphocytes to optimize interactions.

70
Q

The Lymphatic System

A
  • a network that transports fluids from tissues through lymph nodes and ultimately to the circulatory system (initially to veins)
  • excess interstitial fluid is collected by the lymphatic system and is processed by lymph nodes prior to being deposited into the circulatory system.
  • unlike the circulatory system, the lymphatic system is not closed and has no central pump.
71
Q

What happens in the lymphatic system during an immune response?

A
  1. APCs drain from peripheral tissues into lymph nodes.
  2. T lymphocytes enter lymph nodes
  3. APCs activate T Lymphocytes
  4. Lymphocytes exit lymph nodes and enter circulation, then exit circulation into inflamed tissue where they mediate microbial destruction.
72
Q

Secondary lymphoid organs have regions that are rich in certain cell types. What are these organs and cell types?

A
  1. Cortex- B-cell rich
  2. Paracortex- T-cell and DC rich
  3. Medulla