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immunology > Adaptive immune system : B and T Cells > Flashcards

Adaptive immune system : B and T Cells Flashcards

1
Q

What are the two main components involved in adaptive immune responses?

A

Cellular and humoral components.

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2
Q

What are the three stages of the adaptive immune response?

A

Recognition of antigen
Activation of lymphocytes (B and T cells)
Attack against antigen and creation of memory.

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3
Q

Which cells are activated during the adaptive immune response?

A

B and T cells (lymphocytes).

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4
Q

What is the significance of the attack against the antigen in the adaptive immune response?

A

It leads to the destruction of the antigen and the creation of immune memory.

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5
Q

How is vaccination related to the adaptive immune response?

A

Vaccination leverages the stages of the adaptive immune response to create memory, offering protection against future infections.

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6
Q

What are two key features of adaptive immune responses?

A

Specificity and diversity.

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7
Q

What is the importance of memory in adaptive immune responses?

A

Memory allows the immune system to respond faster and more effectively upon subsequent exposure to the same antigen.

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8
Q

What is clonal expansion in the adaptive immune response?

A

The process where specific lymphocytes rapidly multiply after recognizing an antigen, increasing the number of cells that can fight the infection.

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9
Q

What does specialisation refer to in adaptive immunity?

A

It refers to the immune system’s ability to tailor responses to specific types of pathogens (viruses, bacteria, etc.).

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10
Q

What happens during contraction and homeostasis in the immune response?

A

After an infection is cleared, most activated immune cells die off, returning the system to a stable state.

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11
Q

What is non-reactivity to self in adaptive immunity?

A

It’s the ability of the immune system to distinguish between self and non-self, preventing attacks on the body’s own cells (self-tolerance).

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12
Q

Where do B and T lymphocytes originate?

A

They develop in the bone marrow from a haematopoietic stem cell (HSC).

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13
Q

What is the common precursor to B and T cells?

A

Common lymphoid progenitors (CLPs).

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14
Q

Where are immature B cells found, and where do mature B cells go?

A

Immature B cells are found in the bone marrow, and mature B cells move to peripheral lymphoid organs.

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15
Q

Where do B cells and T cells differentiate?

A

B cells remain in the bone marrow, while T cells migrate to the thymus to mature.

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16
Q

What are the early stages of B cell maturation?

A

Hematopoietic Stem Cell (HSC)
Pro-B cell (early and late)

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16
Q

What happens to B cells during maturation in terms of markers?

A

New markers are added at each stage of B cell development on the surface of the cell.

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17
Q

Where are immature B cells located, and where do they mature?

A

Immature B cells are found in the bone marrow, and they mature in the periphery (lymphoid organs).

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17
Q

What significant genetic event occurs during B cell maturation?

A

Re-arrangements of immunoglobulin gene segments occur, leading to the creation of a unique B cell receptor (BCR) by the time the cell reaches the immature B cell stage.

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17
Q

What are the stages of B cell maturation after the Pro-B cell?

A

Large Pre-B cell
Small Pre-B cell

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18
Q

What is the B cell receptor (BCR)?

A

The BCR is an immunoglobulin (IgM molecule) found on the surface of an immature B cell.

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18
Q

What type of immunoglobulin is the BCR similar to?

A

The BCR is similar to a free antibody, specifically IgM.

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19
Q

Where is the BCR found on a B cell?

A

The BCR is found on the surface of an immature B cell in the bone marrow.

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20
Q

Why is each immature B cell’s BCR unique?

A

Each BCR is unique due to the rearrangement of immunoglobulin gene segments during B cell development

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21
Q

Where are B cells generated and selected?

A

In the bone marrow.

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22
Q

What receptor do B cells express?

A

B cells express a B cell receptor (BCR) that recognizes antigens.

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23
Q

Are all B cell receptors (BCRs) the same?

A

No, each BCR is different and unique to each B cell.

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24
Q

How are BCRs generated?

A

Through recombination of genes, a process similar to how T cell receptors (TCRs) are generated.

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25
Q

What is another name for Immunoglobulin (Ig)?

A

Antibody.

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26
Q

How many polypeptides make up an immunoglobulin molecule?

A

Four interlinked polypeptides.

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27
Q

What are the two types of chains in an immunoglobulin molecule?

A

Two long heavy chains
Two short light chains

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28
Q

How many classes of immunoglobulins do mammals have?

A

Five classes: IgM, IgG, IgE, IgA, and IgD.

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29
Q

Which class of immunoglobulin is found in all vertebrates?

A

IgM.

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30
Q

Which two immunoglobulins are the most abundant in mammals?

A

IgM (pentamer) and IgG.

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31
Q

What is the primary role of IgM and IgG antibodies?

A

They provide the bulk of specific immunity against bacteria and viruses in extracellular fluid.

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32
Q

What is the role of IgE antibodies?

A

IgE participates in defenses against multicellular parasites and triggers allergic responses.

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33
Q

Where are IgA antibodies secreted, and what do they protect?

A

IgA (dimer) is secreted by plasma cells in the linings of the gastrointestinal, respiratory, and genitourinary tracts to provide local protection.

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33
Q

What is a major function of IgA in mammals?

A

It is the major antibody found in milk.

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34
Q

What is known about the function of IgD antibodies?

A

The function of IgD is unclear.

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35
Q

What part of the antibody binds to a specific antigen?

A

The variable region.

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35
Q

Do all antibodies recognize the same antigen?

A

No, different antibodies recognize and bind to different antigens or different parts of the same antigen.

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36
Q

What is the binding site of an antibody called?

A

The epitope.

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37
Q

What are the two types of epitopes antibodies can recognize?

A

Epitopes can be based on a linear sequence of the antigen or on its folding structure.

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38
Q

What are the main types of antigens?

A

Foreign antigens (heteroantigens)
Self-antigens (autoantigens)
Cancer cell-derived antigens (neoantigens)

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39
Q

What is the specific site on an antigen recognized and bound by an antibody called?

A

The epitope.

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39
Q

What is an antigen?

A

An antigen is a substance capable of stimulating an immune response.

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40
Q

What are examples of foreign antigens?

A

Microbes, proteins, large polysaccharides, complexed lipids, and nucleic acids.

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41
Q

What does the variable region of an antibody do?

A

The variable region varies among different B cells and specifically recognizes and binds to an antigen.

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42
Q

What is the constant region of an antibody also known as?

A

The Fc domain.

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43
Q

Are the constant regions identical for all antibodies of a given class?

A

Yes, the constant region (Fc domain) is identical for all antibodies within a specific class.

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44
Q

How is the B cell receptor (BCR) activated?

A

The BCR is activated by antigens and by cytokines from Helper T cells (T-dependent activation).

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45
Q

What are the three stages of adaptive immunity?

A

The humoral arm, carried out by B cells, is one of the three stages of adaptive immunity.

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45
Q

What is the role of specific antigen-binding sites on antibodies?

A

They allow antibodies to bind selectively to their corresponding antigens.

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46
Q

What happens to B cells upon activation?

A

Activated B cells proliferate into plasma cells that produce antibodies, and some differentiate into memory cells.

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47
Q

What is the primary role of B cells in humoral immunity?

A

They provide major defense against bacteria, viruses, other microbes in extracellular fluid, and against toxins.

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48
Q

What is the first stage of adaptive immune responses?

A

Recognition of antigen.

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49
Q

What happens in the third stage of adaptive immune responses?

A

Attack against the antigen and creation of memory.

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50
Q

What occurs in the second stage of adaptive immune responses?

A

Activation of lymphocytes (B and T cells).

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51
Q

What is the significance of memory in adaptive immune responses?

A

Memory allows for a faster and more effective immune response upon subsequent exposure to the same antigen.

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52
Q

What does each B lymphocyte possess for recognizing antigens?

A

Each B lymphocyte has a membrane receptor known as the B cell receptor (BCR).

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53
Q

What happens when an antigen binds to a lymphocyte receptor?

A

The antigen is “recognized” by the lymphocyte.

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54
Q

How specific is each lymphocyte in terms of antigen recognition?

A

Each lymphocyte is specific for just one type of antigen.

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55
Q

What happens to a lymphocyte upon binding to its specific antigen?

A

The lymphocyte undergoes cell division to make clones.

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56
Q

What are the two main functions of the clones produced from activated lymphocytes?

A

Plasma cells that carry out the attack on the antigen.
Memory cells for future encounters with the same antigen.

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57
Q

What role do plasma cells play in the immune response?

A

Plasma cells produce antibodies to attack the antigen.

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58
Q

What is the purpose of memory cells in the immune system?

A

Memory cells provide a faster and more effective response to future encounters with a particular antigen.

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59
Q

What is the process called when an antigen stimulates a lymphocyte to divide?

A

Clonal selection

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60
Q

What happens to an antigen-stimulated lymphocyte during T-dependent activation?

A

The lymphocyte divides and replicates itself.

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61
Q

What is true about the progeny of an activated lymphocyte?

A

All progeny express the same receptor as the original lymphocyte.

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62
Q

What do activated B cells differentiate into during the attack against antigens?

A

Activated B cells differentiate into plasma cells that secrete antibodies.

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63
Q

What role do activated cytotoxic T cells play in the immune response?

A

Activated cytotoxic T cells carry out the attack against infected or cancerous cells.

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64
Q

How long do plasma cells typically live after activation?

A

Plasma cells are short-lived.

65
Q

What is the initial stage of B cell differentiation?

A

B cells begin as hematopoietic stem cells (HSC) in the bone marrow.

66
Q

What happens to B cells during maturation in the bone marrow?

A

They undergo several stages, developing specific markers, and rearranging immunoglobulin genes to form unique B cell receptors (BCRs).

67
Q

How are immature B cells characterised?

A

Immature B cells express B cell receptors (BCRs) and undergo selection processes to ensure functionality and self-tolerance.

68
Q

What do plasma cells do?

A

Plasma cells secrete antibodies to target and neutralize specific antigens.

68
Q

What occurs when an immature B cell successfully binds to an antigen?

A

It becomes activated, undergoes clonal expansion, and differentiates into plasma cells and memory cells.

69
Q

What is one of the main functions of antibodies?

A

Neutralization of antigens.

70
Q

What is the role of memory B cells?

A

Memory B cells persist in the body to provide a faster and more effective response upon re-exposure to the same antigen.

71
Q

What system do antibodies help to activate?

A

The complement system.

71
Q

How do antibodies assist in opsonization?

A

Antibodies coat bacteria, making them easier for phagocytes to recognize and engulf.

72
Q

What is ADCC in the context of antibody function?

A

Antibody-dependent cellular cytotoxicity (ADCC) refers to the ability of antibodies to aid in killing infected or cancerous cells.

73
Q

What is the role of B cells in the adaptive immune system?

A

B cells are part of the adaptive humoral immune system and produce antigen-specific immunoglobulins, typically known as antibodies.

74
Q

What is the main function of T cells in the adaptive immune system?

A

T cells play a central role in adaptive immunity.

75
Q

What are the two main types of immune responses mediated by T cells?

A

Cell-mediated immunity and help in activating B cells.

76
Q

How do T cells assist B cells in the adaptive immune response?

A

Certain types of T cells, such as Helper T cells, provide signals and cytokines that activate B cells and enhance antibody production.

77
Q

Where do T cells develop?

A

T cells develop in the bone marrow and mature in the thymus.

78
Q

What is the purpose of T cell development?

A

The purpose is to generate a diverse collection of T cell receptors (TCRs).

79
Q

What can be said about the types of T cells?

A

There are many different types of T cells, each with specific functions in the immune response.

80
Q

Why is the diversity of T cell receptors important?

A

It allows the host to mount an adaptive immune response against a wide range of pathogens.

81
Q

Where are T cells selected during their development?

A

T cells are selected in the thymus.

82
Q

What happens to T cells after they mature in the thymus?

A

They migrate into the periphery.

83
Q

How do T cells move through the body?

A

T cells circulate through lymph nodes.

84
Q

What occurs when a T cell recognizes an antigen?

A

The T cell activates and acquires effector functions.

85
Q

What does the adaptive immune system generate in terms of antigen specificity

A

A diverse range of antigen-specific cells.

86
Q

What do the antigen-specific cells in the adaptive immune system recognize?

A

They recognize different antigens.

87
Q

What is a potential issue with some of the antigen-specific cells generated?

A

Some of these cells may be specific for self-antigens.

88
Q

What is the significance of clonal selection in the immune response?

A

Clonal selection ensures that only the lymphocytes that recognize and bind to a specific antigen are activated and proliferated.

89
Q

Why is clonal deletion important in the immune system?

A

It prevents lymphocytes with self-reactive receptors from becoming problematic by recognizing self-antigens.

90
Q

What happens to T cells that receive too little or too much of a signal during selection?

A

They are deleted through a process called apoptosis.

91
Q

What is another mechanism, besides apoptosis, that helps regulate self-reactive T cells?

A

Inducing an inactive state called anergy.

92
Q

What is the significance of inducing anergy in self-reactive lymphocytes?

A

Anergy prevents self-reactive lymphocytes from becoming activated and causing autoimmune responses.

93
Q

What is one critical feature of lymphocyte development that distinguishes adaptive immunity?

A

Each lymphocyte expresses only one receptor specificity.

94
Q

How is a lymphocyte’s DNA altered during development?

A

The lymphocyte’s DNA is irreversibly altered by gene rearrangement.

95
Q

What are the two main types of protein chains that make up the T cell receptor (TCR)?

A

Often alpha (α) and beta (β) chains; sometimes gamma (γ) and delta (δ) chains.

95
Q

What does the gene rearrangement during T cell development ensure?

A

It ensures that all progeny inherit the same receptor specificity.

96
Q

What is the term used to describe the proliferation of an individual T cell into clones with identical antigen receptors?

A

Clonal expansion.

97
Q

: What is the role of the variable regions in the TCR?

A

The variable regions recognize the diversity of antigens.

98
Q

What is the structural characteristic of the TCR?

A

It is a transmembrane protein with a cytoplasmic tail.

99
Q

What happens upon recognition of an antigen by the TCR?

A

Signaling occurs that activates the T cell.

100
Q

How is the T cell receptor (TCR) generated?

A

The TCR is generated by random recombination and mutation of germline DNA for both TCR chains.

101
Q

What is the significance of the random recombination and mutation in TCR generation?

A

It results in different TCRs for each T cell, allowing each T cell to recognize a different antigen.

102
Q

Why is it important that each T cell recognizes a different antigen?

A

This diversity enables the immune system to respond to a wide range of pathogens.

103
Q

What does the T cell receptor (TCR) generate?

A

A huge diversity of antigen-specific T cells.

104
Q

Why might not all T cells generated be useful?

A

Some T cells may recognize self-antigens, leading to potential autoimmune responses.

105
Q

What happens to T cells that do not recognize MHC (major histocompatibility complex)?

A

They are not activated and may undergo deletion during the selection process.

106
Q

What is the purpose of T cell selection?

A

To ensure that only T cells that recognize foreign antigens presented by MHC molecules are allowed to mature and proliferate.

107
Q

Where are T cells selected?

A

T cells are selected in the thymus.

108
Q

What is tested during T cell selection in the thymus?

A

The T cell receptor (TCR) is tested to confirm that it functions properly and does not recognize self-antigens

109
Q

How is the selection of T cells based on affinity?

A

T cells with strong affinity for self-antigens are deleted, while those with appropriate affinity for foreign antigens are retained.

110
Q

What types of cells do useful T cells differentiate into?

A

They differentiate into either CD4+ ‘helper’ T cells or CD8+ ‘killer’ T cells.

111
Q

What are the two main subsets of T cells?

A

CD4+ ‘helper’ T cells and CD8+ ‘killer’ T cells.

112
Q

What is the role of CD4+ ‘helper’ T cells?

A

They assist other immune cells, including B cells and CD8+ T cells, in mounting an effective immune response

113
Q

What percentage of αβ T cells are CD4 and CD8 subsets?

A

CD4 and CD8 subsets comprise the bulk of αβ T cells and are the main components of T-mediated immune responses.

113
Q

What is the primary function of CD8+ ‘killer’ T cells?

A

They directly kill infected or cancerous cells.

114
Q

Are there further subsets of T cells beyond CD4+ and CD8+?

A

Yes, there are further subsets of T cells derived from both CD4+ and CD8+ T cells.

115
Q

What do T cells recognize in the immune response?

A

T cells recognize short peptides generated from pathogen-associated proteins.

116
Q

How are these short peptides generated?

A

They are produced by phagocytes (innate cells) that digest pathogens.

117
Q

What is the term used for the short peptides that T cells recognise?

A

Antigens.

118
Q

Why is it important for T cells to recognize these short peptides?

A

Recognizing these peptides allows T cells to identify and respond to infected or abnormal cells.

119
Q

How are peptides recognized by T cells?

A

Peptides are presented to the T cell receptor (TCR) in the context of Major Histocompatibility Complex (MHC).

120
Q

What are the two forms of MHC?

A

MHC-I and MHC-II.

121
Q

Which T cell subset interacts with MHC-II molecules?

A

CD4+ T cells.

121
Q

Which T cell subset interacts with MHC-I molecules?

A

CD8+ T cells.

122
Q

Where are MHC class I molecules expressed?

A

MHC class I molecules are expressed on all mammalian cells, including cells of epithelial origin.

123
Q

Where are MHC class II molecules selectively expressed?

A

MHC class II molecules are selectively expressed on professional antigen-presenting cells, including dendritic cells, macrophages, and B cells.

124
Q

How are antigens recognized when they are engulfed from outside the cell?

A

Antigens engulfed from outside the cell (e.g., bacteria) are presented via MHC II to CD4+ T cells.

125
Q

How are antigens presented when they come from inside the cell?

A

Antigens presented from inside the cell (e.g., viruses) are displayed via MHC I to CD8+ T cells.

126
Q

What determines how antigens are presented to T cells?

A

The right stimulus determines how antigens are presented to T cells.

127
Q

Which type of cells are very effective at presenting antigens?

A

Dendritic cells are very good at presenting antigens via both MHC I and MHC II.

128
Q

What do naïve antigen-specific T cells do?

A

They recirculate looking for phagocytes presenting their cognate antigen.

129
Q

What occurs upon recognition of the antigen/MHC by a T cell?

A

The T cell and antigen-presenting cell form an interaction.

130
Q

What role does the T cell receptor (TCR) play upon antigen recognition?

A

The TCR transmits signals that activate the T cell.

131
Q

What is the outcome of T cell activation?

A

The activated T cell will proliferate and differentiate into effector cells that perform various immune functions.

132
Q

Why is the proliferation of T cells necessary after activation?

A

The huge diversity of T cells means that antigen-specific T cells are rare, so they need to proliferate to generate an effective immune response.

133
Q

What happens to activated T cells during proliferation?

A

Activated T cells proliferate rapidly and differentiate into functional effector T cells.

134
Q

What are effector T cells responsible for?

A

Effector T cells carry out various immune functions, including killing infected cells and helping other immune cells.

135
Q

How does the proliferation of T cells contribute to the immune response?

A

It increases the number of antigen-specific T cells, enhancing the body’s ability to fight off infections.

136
Q

What are the effector functions of CD4+ T cells?

A

CD4+ T cells have a ‘helper’ function, assisting other immune cells in the immune response.

137
Q

What is the primary function of CD8+ T cells?

A

CD8+ T cells have a ‘killer’ function, directly killing infected or cancerous cells.

138
Q

What factors determine whether T-helper cells differentiate into Th1 or Th2 cells?

A

The type of cytokines present during activation and the nature of the antigen (e.g., intracellular vs. extracellular pathogens) influence whether T-helper cells become Th1 or Th2.

139
Q

What is the function of Th1 cells in the immune response?

A

Th1 cells secrete IFN-γ and activate macrophage functions.

139
Q

What is the role of Th1 cells?

A

Th1 cells primarily help activate macrophages and are important for the immune response against intracellular pathogens.

139
Q

What is the role of Th2 cells?

A

Th2 cells assist in activating B cells and are important for the immune response against extracellular pathogens, particularly in allergic responses.

139
Q

How do Th1 and Th2 cells differ in their immune functions?

A

Th1 cells are involved in activating macrophages for intracellular pathogen defense, while Th2 cells focus on aiding antibody production against extracellular pathogens

139
Q

What happens to the number of T cells specific for an antigen after an infection?

A

The number of T cells specific for the antigen increases dramatically and then drops off.

140
Q

What cytokine is primarily secreted by Th2 cells?

A

Th2 cells secrete IL-4.

141
Q

What role do Th2 cells play in the immune response?

A

Th2 cells help promote antibody production by B cells.

142
Q

What is left after the initial increase in T cells post-infection?

A

A low level of memory T cells remains.

143
Q

Why is the presence of memory T cells significant?

A

Memory T cells are a key feature of the ‘adaptive’ immune system, allowing for a quicker and more effective response upon re-exposure to the same antigen.

144
Q

How does the adaptive immune system differ from the innate immune system in terms of memory?

A

The adaptive immune system has memory T cells that provide long-lasting immunity, whereas the innate immune system does not have this memory capability.

145
Q

Do memory T cells need additional signals for proliferation?

A

yes, memory T cells still require the correct signals to allow proliferation.

145
Q

What is required for the survival of memory T cells?

A

Memory T cells require sustained stimulation by IL-7 and IL-5 for survival.

145
Q

What role do vaccines play in T cell memory?

A

Vaccines stimulate the adaptive immune system to produce memory T cells against specific pathogens without causing the disease.

146
Q

What is the role of IL-7 in memory T cell maintenance?

A

IL-7 promotes the survival of memory T cells by providing essential survival signals.

147
Q

What is the role of IL-5 in memory T cell functions?

A

IL-5 aids in the growth and differentiation of memory T cells, enhancing their response capabilities.

148
Q

What is a potential issue with recognizing self-antigens in the adaptive immune system?

A

Not all antigens are harmful; self-antigens can lead to autoimmunity if misrecognized.

149
Q

Why is cross-talk important between the innate and adaptive immune systems?

A

Cross-talk helps control immune responses, preventing harmful reactions to non-harmful antigens.

150
Q

What are “danger” signals?

A

Danger signals are alarm signals from injured or stressed cells that alert the immune system to potential threats

151
Q

What does the random generation of specificity in adaptive immunity allow?

A

It allows the lymphocyte population to recognize antigenic peptides from many potential pathogens.

151
Q

What is a disadvantage of the random specificity in adaptive immunity?

A

It can lead to autoimmunity, allergies, and food sensitivities if the immune system mistakenly targets non-harmful substances.

152
Q

How does adaptive immunity help prevent pathogen evasion?

A

It allows for the recognition and targeting of diverse antigenic peptides, stopping pathogens from evading the immune system.

153
Q

What activates the immune system?

A

The immune system is activated by inflammatory inducers that indicate the presence of pathogens or tissue damage.

153
Q

How quickly does innate immunity respond to threats?

A

Innate immunity is normally initiated within minutes, with the initial response observable within hours.

154
Q

How does the timeline of the adaptive immune response differ from innate immunity?

A

The adaptive immune response takes over later, with a variable timeline that can span days to weeks, and even years if the infection persists.

155
Q

What is a critical aspect of the adaptive immune response?

A

The critical induction of memory, including the production and maintenance of memory T cells, is a key aspect of the adaptive immune response.

156
Q

What role do memory T cells play in the immune response?

A

Memory T cells enable a quicker and more robust response to previously encountered pathogens upon re-exposure.

157
Q
A

immunology (4 decks)

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