F. Immunology (1) Flashcards
(137 cards)
1
Q
What is immunology?
A
● Immunology is the branch of biology that focuses on the study of the body’s defense mechanisms against infections and threats posed by cells within the body.
2
Q
What is the immune system composed of? (3)
A
The primary or central lymphoid organs are the bone marrow and the thymus.
The bone marrow is responsible for producing myeloid cells, natural killer cells, B lymphocytes, and T lymphocytes.
The thymus is where immature precursor cells of T lymphocytes migrate from the bone marrow and complete their development.
3
Q
What is Innate immunity? (3)
A
● Innate immunity is the initial response of the host to an infection.
It serves as the first line of defense.
Innate immunity involves a combination of anatomical barriers and associated factors.
4
Q
What are the physical barriers? (2)
A
The physical barriers include the epithelium of the skin, respiratory tract, intestinal tract, and urogenital tract.
These barriers possess mechanical, biochemical, and microbial factors that prevent the entry of pathogens. For example, the skin acts as a physical barrier, while the secretion of tears, mucous secretions, and antimicrobial substances provide additional protection.
5
Q
What happens if these barriers are breached?
A
Innate immune cells have receptors that recognize common components found in the walls of pathogens or microbes, such as lipopolysaccharides, mannose, or
complement/antibodies that opsonize the pathogen. These receptors are not specific to a particular microbe but rather recognize components that are common to many different microbes.
6
Q
● Innate immune cells can be divided into two main categories:
A
Those that phagocytose and kill invading pathogens, and those that kill infected cells of the body.
7
Q
The former category includes macrophages, neutrophils, basophils, mast cells, eosinophils, and dendritic cells. These cells can ____ and _____ pathogens or release granules that are toxic to the invaders.
A
engulf
destroy
8
Q
The latter category comprises natural killer cells, which recognize infected cells _____ intracellular viruses or bacteria and eliminate them.
A
harboring
9
Q
Receptors for pathogen surface components or molecules released from dying or damaged cells: (2)
A
Mannose Receptor: Recognizes mannose, a sugar molecule commonly found on the surface of pathogens.
Lipopolysaccharide (LPS) Receptor: Binds to lipopolysaccharides, which are molecules present on the outer membrane of certain bacteria.
10
Q
● Receptors for opsonins: (3)
A
Fc Receptors (FcR)
Complement Receptors (CR)
Pattern Recognition Receptors (PRRs)
11
Q
What are Fc Receptors (FcR)?
A
These receptors recognize the Fc (constant) region of antibodies. Antibodies, produced by B cells in response to pathogens, can bind to specific antigens on the surface of the pathogens. When antibodies attach to pathogens, the Fc region becomes accessible for binding to Fc receptors on immune cells. This process, known as opsonization, marks the pathogen for phagocytosis by immune cells.
12
Q
What are Complement Receptors (CR)?
A
Complement is a group of proteins that can bind to pathogens and enhance their clearance. Complement receptors on immune cells recognize specific complement proteins, such as C3b, bound to the surface of pathogens. This binding triggers various immune responses, including phagocytosis.
13
Q
What are the types of Pattern Recognition Receptors (PRRs)? (2)
A
✔ Toll-like Receptors (TLRs)
✔ Nod-like Receptors (NLRs)
14
Q
What are ✔ Toll-like Receptors (TLRs)?
A
These receptors recognize specific molecular patterns associated with pathogens, known as pathogen-associated molecular patterns
(PAMPs). TLRs can detect molecules like lipopolysaccharides, flagellin, and viral RNA. When TLRs bind to PAMPs, they initiate immune responses to eliminate the pathogens.
15
Q
What are ✔ Nod-like Receptors (NLRs)?
A
NLRs recognize molecules released by damaged cells, known as damage-associated molecular patterns (DAMPs). DAMPs are released
during cell stress, injury, or cell death. Examples of DAMPs include ATP and uric acid. NLRs can trigger immune responses to remove the sources of cellular damage.
16
Q
What is Phagocytosis?
A
● Phagocytes, including macrophages, neutrophils, dendritic cells, and eosinophils, play a crucial role in protecting the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. This process is called phagocytosis.
17
Q
● Phagocytosis is a form of endocytosis, where the phagocyte binds to the pathogen or microbe via specific receptors on its surface.
What is the full process? (7)
A
- In addition to the oxidative burst, phagocytes also employ oxygen-independent mechanisms to kill and degrade pathogens. These mechanisms involve the release of
enzymes and toxic molecules within the phagolysosome. Enzymes such as lysozyme, nucleases, proteases, glycosidases, lipases, phosphatases, and sulphatases degrade the pathogens or antigens, breaking them down into smaller, harmless components. - Once the pathogens or microbes are degraded, the remaining indigestible and residual material is removed from the phagocyte through exocytosis.
18
Q
What is the Complement?
A
● Complement is a group of proteins that are produced by the liver and circulate in the blood as part of the innate immune system. These proteins play a crucial role in the defense against infections.
19
Q
Complement:
What happens when an infection occurs? (2)
A
● When an infection occurs, complement pathways are activated. Activation can be initiated through various mechanisms, such as the binding of antibodies to pathogens or the direct recognition of pathogen-associated molecular patterns (PAMPs) by complement proteins.
● Once activated, the complement proteins are cleaved into smaller fragments, which carry out different functions.
20
Q
● Some of the functions of complement fragments include: (5)
A
Chemo-attraction
Opsonization
Membrane attack complex (MAC) formation
Complement activation
Acute phase
21
Q
What is Chemo-attraction?
A
Fragments such as C3a and C5a act as chemo-attractants, attracting immune cells to the site of infection. These fragments help recruit and activate other immune cells, enhancing the immune response.
22
Q
What is Opsonization?
A
The fragment C3b acts as an opsonin. It can bind to the surface of pathogens, coating them and marking them for recognition and engulfment by phagocytic cells. Opsonization facilitates the clearance of pathogens by phagocytes.
23
Q
What is the Membrane attack complex (MAC) formation?
A
The complement proteins C5b, C6, C7, C8, and multiple copies of C9 can assemble to form the membrane attack complex (MAC). MAC creates a pore or channel in the cell membrane of pathogens or microbes, leading to cell lysis. This pore disrupts the integrity of the pathogen’s membrane, resulting in its destruction.
24
Q
What is the Complement activation?
A
Complement activation is an essential component of the immune response and works in coordination with other immune cells and mechanisms to eliminate pathogens. It helps initiate inflammation, enhance phagocytosis, and directly destroy the pathogens.
25
Acute phase proteins are a group of proteins produced by the liver in response to inflammation and activation of immune cells such as macrophages and neutrophils. These proteins are part of the acute phase response, which is a rapid and nonspecific reaction to infection, injury, or inflammation.
Two examples of acute phase proteins are:
✔ C-reactive protein (CRP)
✔ Mannose-binding lectin (MBL)
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What is ✔ C-reactive protein (CRP)?
CRP binds to bacterial and fungal cell walls, activating complement and enhancing phagocytosis. Elevated levels of CRP in the blood are a marker of inflammation and infection.
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What is ✔ Mannose-binding lectin (MBL)?
MBL recognizes specific sugar molecules on the surface of pathogens and triggers the complement cascade. It acts as an opsonin and enhances phagocytosis.
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What is the adaptive immune response? (2)
● The adaptive immune response is a specific and highly targeted response mediated by lymphocytes, including B lymphocytes and T lymphocytes.
● This response is characterized by the recognition of unique receptors on each lymphocyte that are specific for either a peptide associated with a major histocompatibility complex (MHC) protein (T cell) or an epitope on the pathogen or microbe (B cell).
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● The adaptive immune response consists of the following components: (4)
B lymphocytes (B cells)
T lymphocytes (T cells)
Memory cells
Secondary lymphoid organs
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What are B lymphocytes (B cells)?
B cells possess a B cell receptor (BCR) on their surface. Each B cell has a unique BCR that recognizes a specific epitope on a pathogen or microbe. When a BCR binds to its corresponding antigen, the B cell is activated.
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What are T lymphocytes (T cells)?
T cells have a T cell receptor (TCR) on their surface. The TCR recognizes peptides presented by MHC proteins on the surface of antigen-presenting cells.
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T cells can be further classified into two main types:
✔ CD8 T cells (cytotoxic T cells)
✔ CD4 T cells (helper T cells)
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What are ✔ CD8 T cells (cytotoxic T cells)?
CD8 T cells are involved in directly killing infected cells. They recognize and bind to antigens presented by MHC class I
molecules on the surface of infected cells, leading to the destruction of the infected cells.
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What are ✔ CD4 T cells (helper T cells)?
CD4 T cells play a crucial role in coordinating and regulating immune responses. They recognize antigens presented by MHC class II molecules on the surface of antigen-presenting cells and provide help to other immune cells.
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What are Memory cells?
Memory cells are also produced during the adaptive immune response. These cells are long-lived and retain the ability to recognize specific antigens.
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What are Secondary lymphoid organs?
Secondary lymphoid organs, including lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT), play a crucial role in the adaptive immune response.
37
What are Secondary lymphoid organs?
Secondary lymphoid organs, including lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT), play a crucial role in the adaptive immune response.
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✔ Lymph nodes serve as sites where _______ meet antigen-presenting cells carrying engulfed pathogens or microbes.
lymphocytes
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What is the function of the spleen?
✔ The spleen traps pathogens or microbes present in the blood and activates naive lymphocytes.
40
What is the function of the spleen?
✔ The spleen traps pathogens or microbes present in the blood and activates naive lymphocytes.
41
What is the function of MALT?
✔ MALT, found in mucosal tissues such as tonsils, Peyer's patches, and the appendix, allows resident dendritic cells to engulf pathogens entering through the mucosa and activate naive lymphocytes in the mucosal compartments.
42
What is the innate immune system? (3)
● The innate immune system is the body's first line of defense against infections.
● It is a non-specific immune response that provides immediate protection upon encountering
pathogens.
● The innate immune system recognizes common patterns associated with pathogens and triggers a response to eliminate them.
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Immune system:
● It includes _______ barriers, chemical defenses, and various immune cells.
physical
44
What are barriers? (2)
● These are physical barriers of the body that serve as the first line of defense against pathogens.
● The skin acts as a protective barrier that prevents the entry of microorganisms.
45
What are the types of epithelia? (3)
- Respiratory epithelia
- Intestinal epithelia
- Urogenital epithelia
46
What is Respiratory epithelia?
● Respiratory epithelia line the respiratory tract and help filter out pathogens from the air we
breathe.
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What is Intestinal epithelia?
● Intestinal epithelia line the intestines and play a role in preventing the invasion of harmful
microorganisms from the gut.
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What is Urogenital epithelia?
● Urogenital epithelia line the urinary and reproductive tracts, providing a barrier against pathogens.
49
What are the functions of neutrophils? (4)
● Phagocytosis
● Killing Mechanisms
● Neutrophil Extracellular Traps (NETs)
● Cytokine Release
50
How do neutrophils function in phagocytosis? (3)
Neutrophils can recognize pathogens through various receptors, including Toll-like receptors (TLRs).
They can engulf and destroy pathogens through phagocytosis.
Neutrophils also have receptors for opsonized antigens, which are antigens marked with antibodies or complement proteins.
51
How do neutrophils function as killing mechanisms? (3)
After engulfing the pathogen, neutrophils use oxygen-dependent and oxygen-independent mechanisms to kill pathogens.
Oxygen-dependent mechanisms involve the production of reactive oxygen species (ROS) that have antimicrobial effects.
Neutrophils can also release antimicrobial substances, such as defensins and lactoferrin, from their granules.
52
How do neutrophils function in Neutrophil Extracellular Traps (NETs)? (2)
Neutrophils can release their chromatin (DNA and histones) along with antimicrobial molecules, forming neutrophil extracellular traps (NETs).
NETs can trap and kill pathogens, particularly those too large to be engulfed.
53
How do neutrophils function in Cytokine Release?
Neutrophils can secrete cytokines, including interferon-gamma (IFNγ), which plays a role in
macrophage activation and increased expression of major histocompatibility complex (MHC) proteins.
54
What are Eosinophils? (2)
● Eosinophils are a type of white blood cell involved in the immune response against parasites, particularly helminths (worms).
● They have toxic granules and can release reactive oxygen species (ROS) and other highly toxic substances to kill extracellular parasites.
55
● Eosinophils also contribute to the ________ of immune responses through the synthesis of prostaglandins and cytokines, promoting inflammation.
● Their levels increase in response to the secretion of interleukin-5 (_____) by T-helper 2 (_____) cells.
● Additionally, eosinophils can act as phagocytes and are involved in _____ responses.
amplification
(IL-5)
(Th2)
allergic
56
What are basophils?
● Basophils are another type of white blood cell involved in allergic responses and inflammation.
57
What receptors do basophils have?
● They have receptors for immunoglobulin E (IgE) antibodies and release histamine and interleukin-4 (IL-4) when activated.
58
● Basophils promote the development of ____ cells, which are involved in allergic responses.
Th2
59
What are mast cells? (2)
● Mast cells are sentinel cells found in the skin, mucosal epithelium, and connective tissues.
● They are involved in the rapid release of proinflammatory cytokines and lipid mediators in
response to infections and other stimuli.
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What are mast cells? (2)
● Mast cells are sentinel cells found in the skin, mucosal epithelium, and connective tissues.
● They are involved in the rapid release of proinflammatory cytokines and lipid mediators in
response to infections and other stimuli.
61
● Mast cells express receptors for ____antibodies (Fc receptors) and toll-like receptors (TLRs).
IgE
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What happens when mast cells are activated? (3)
● When activated, they release histamine, which causes vasodilation and increased capillary permeability, leading to acute inflammation.
● Mast cells also play a role in defense against helminths.
● They have a lifespan of weeks to months.
63
What happens when mast cells are activated? (3)
● When activated, they release histamine, which causes vasodilation and increased capillary permeability, leading to acute inflammation.
● Mast cells also play a role in defense against helminths.
● They have a lifespan of weeks to months.
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What are natural killer cells?
● Natural killer cells are lymphoid lineage cells that play a vital role in controlling viral infections and killing cancer cells.
65
What is the function of natural killer cells?
● They recognize infected cells and cancer cells through various receptors. These include stress receptors (MICA) on infected cells, receptors that bind to MHC class I molecules (KIRs), and receptors for antibodies (Fc receptors).
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How are Nk cells activated?
● NK cells are activated by cytokines such as interferon-alpha (IFNα), interferon-beta (IFNβ), and interleukin-12 (IL-12) produced by dendritic cells, fibroblasts, and macrophages, respectively.
67
How are Nk cells activated?
● NK cells are activated by cytokines such as interferon-alpha (IFNα), interferon-beta (IFNβ), and interleukin-12 (IL-12) produced by dendritic cells, fibroblasts, and macrophages, respectively.
68
● Functions of NK Cells:
- Killing Infected Cells:
NK cells induce apoptosis (cell death) in infected cells through the release of perforin and granzyme. They recognize infected cells that have increased
stress receptors and a lack of MHC class I molecules, which are usually present on healthy cells.
69
● Functions of NK Cells:
Cytokine Secretion
NK cells secrete cytokines, including interferon-gamma (IFNγ). IFNγ activates macrophages, increases MHC expression, and enhances antigen processing. It also plays a role in suppressing the Th2 immune response.
70
● Functions of NK Cells:
Cytokine Secretion
NK cells secrete cytokines, including interferon-gamma (IFNγ). IFNγ activates macrophages, increases MHC expression, and enhances antigen processing. It also plays a role in suppressing the Th2 immune response.
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● NK cells have a lifespan of about ___ weeks
two
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What are Dendritic Cells? (2)
● Dendritic cells are a type of immune cell that plays a vital role in linking the innate and adaptive immune systems.
● They are considered the most important cells in activating naive T cells, which are crucial for adaptive immune responses.
73
What are Dendritic Cells? (2)
● Dendritic cells are a type of immune cell that plays a vital role in linking the innate and adaptive immune systems.
● They are considered the most important cells in activating naive T cells, which are crucial for adaptive immune responses.
74
● Dendritic cells recognize pathogens through receptors such as Toll-like receptors (TLRs) and the _______ receptor.
mannose
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Dendrites:
● They can also recognize opsonized pathogens via complement receptors (CR).
● Once they capture pathogens, dendritic cells phagocytose them and degrade them in
_________.
phagolysosomes
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What happens when dendrites are activated? (2)
● The activation of dendritic cells leads to the production of co-stimulatory proteins and chemokine receptors. They are further activated by interferon-alpha (IFNα) and interferon-beta (IFNβ).
● Following activation, dendritic cells migrate via chemokine gradients to the nearest lymph node, where they present antigens to naive T cells. This presentation of antigens is crucial for initiating adaptive immune responses.
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● Dendritic cells also secrete various _______, including tumor necrosis factor-alpha (TNFα), interleukin-6 (IL-6), interleukin-1 (IL-1), interleukin-12 (IL-12), and interferon-alpha (IFNα).
cytokines
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● These cytokines play diverse roles such as: (5)
✔ enhancing endothelial permeability
✔ promoting inflammation
✔ inducing fever
✔ activating natural killer (NK) cells and Th1 cells
✔ Increasing major histocompatibility complex I (MHCI) expression.
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● The lifespan of dendritic cells can range from ____ to weeks, allowing them to participate in immune responses over an extended period.
days
80
● The lifespan of dendritic cells can range from ____ to weeks, allowing them to participate in immune responses over an extended period.
days
81
What is Extravasation?
● Extravasation refers to the process by which blood cells, such as neutrophils and monocytes, leave the bloodstream and migrate into tissues to fight infection.
82
Extravasation (Movement from Blood to Tissues)
● It involves a series of steps: (4)
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Antibody-Dependent Cellular Cytotoxicity (ADCC)
What is the mechanism?
● ADCC is a mechanism by which certain immune cells, such as natural killer (NK) cells, destroy target cells that are coated with antibodies.
84
Antibody-Dependent Cellular Cytotoxicity (ADCC)
What is the process? (5)
85
What are Granzymes and perforin?
● Granzymes and perforin are molecules released by immune cells, particularly NK cells, during cell-mediated cytotoxicity.
86
What does perforin do?
Perforin forms pores in the membrane of target cells, allowing granzymes to enter the cell.
87
What do granzymes do?
Granzymes are proteases that induce cell death by activating apoptotic pathways or by disrupting cellular functions.
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What is inflammation? (2)
● Inflammation is a complex biological response of the body to injury or infection in tissues.
● It is characterized by heat, pain, redness, and swelling, along with loss of function or
immobility.
89
● Key points about inflammation:
Initiation:
Inflammation is triggered by tissue injury or infection. The presence of pathogens or damaged cells stimulates immune cells, particularly macrophages and mast cells, to release chemokines and cytokines.
90
● Key points about inflammation:
Vasodilation and Increased Permeability:
The released chemokines and cytokines cause vasodilation, leading to increased blood flow to the affected area. This results in localized redness and heat. Additionally, the endothelial cells lining the blood vessels become more permeable, allowing fluid and immune cells to leak into the tissues. The increased fluid accumulation contributes to swelling.
91
● Key points about inflammation:
Vasodilation and Increased Permeability:
The released chemokines and cytokines cause vasodilation, leading to increased blood flow to the affected area. This results in localized redness and heat. Additionally, the endothelial cells lining the blood vessels become more permeable, allowing fluid and immune cells to leak into the tissues. The increased fluid accumulation contributes to swelling.
92
● Key points about inflammation:
Recruitment of Neutrophils and Monocytes:
In response to the chemotactic signals released during inflammation, neutrophils and monocytes (which differentiate into macrophages) are recruited to the affected area from the bloodstream. Neutrophils are the predominant cells to arrive in the first 0-48 hours, followed by macrophages.
93
● Key points about inflammation:
Local Blood Clotting:
Inflammation can induce local blood clotting, forming a barrier that helps prevent the spread of infection to other tissues.
94
● Key points about inflammation:
Activation of Nerve Endings and Pain:
Mediators such as tumor necrosis factor-alpha (TNFα), bradykinin, and histamine stimulate nerve endings, leading to the perception of pain.
95
● Key points about inflammation:
Loss of Function:
The swelling and pain associated with inflammation can result in a temporary loss of function or immobility in the affected area.
96
● Key points about inflammation:
Protective Functions: (4)
✔ Inflammation prevents the spread of damaging agents by isolating the site of
injury or infection.
✔ It removes cellular debris and pathogens through the influx of immune cells and increased vascular permeability.
✔ Inflammation also alerts the adaptive immune system to mount a specific immune response.
✔ Furthermore, the inflammatory response sets the stage for tissue repair and healing processes to begin.
97
Humoral Component: Acute Phase Proteins
What are acute phase proteins?
● During inflammation, the liver produces a group of proteins called acute phase proteins. The production of these proteins is stimulated by cytokines such as interleukin-1 (IL-1) and interleukin-6 (IL-6), which are produced by macrophages and neutrophils.
98
● Acute phase proteins have various functions in the immune response, including: (5)
C-reactive protein (CRP)
Mannose binding lectin (MBL)
Ferritin
Fibrinogen and Factor VIII
Serum Amyloid A
99
What is the function of C-reactive protein (CRP)?
CRP is an opsonin, meaning it enhances the phagocytosis of microbes. It can also activate the classical complement pathway, which leads to the destruction of pathogens.
100
What is the function of Mannose binding lectin (MBL)?
MBL activates the mannose-binding lectin complement pathway, also known as the lectin pathway. This pathway helps eliminate pathogens by promoting their opsonization and destruction.
101
What is the function of Ferritin?
Ferritin binds to iron, restricting its availability to microbes and inhibiting their iron uptake, which is essential for their growth and survival.
102
What is the function of Fibrinogen and Factor VIII?
These proteins are involved in the coagulation cascade, contributing to the formation of blood clots at the site of injury or infection. Blood clotting helps prevent the spread of pathogens.
103
What is the function of Fibrinogen and Factor VIII?
These proteins are involved in the coagulation cascade, contributing to the formation of blood clots at the site of injury or infection. Blood clotting helps prevent the spread of pathogens.
104
What is the function of Serum Amyloid A?
Serum amyloid A is involved in the recruitment of immune cells to inflammatory sites. It contributes to the inflammatory response and facilitates immune cell migration to the affected area.
105
What is the complement?
● Complement is a group of around 30 different plasma proteins produced by the liver. When these proteins are cleaved and activated, they act as a defense mechanism against microbes in extracellular spaces.
106
● Outcome of Complement Activation: (3)
Opsonization
Microbe Lysis
Inflammation
107
● Outcome of Complement Activation:
Opsonization:
Complement proteins, particularly C3b, coat the surface of microbes, enhancing their phagocytosis by phagocytes.
108
● Outcome of Complement Activation:
Microbe Lysis:
Complement activation can lead to the formation of the membrane attack complex (MAC), which consists of multiple complement proteins, including C5b, C6, C7, C8, and multiple copies of C9. The MAC forms pores in the surface of microbes, causing them to undergo lysis and cell death.
109
● Outcome of Complement Activation:
Inflammation:
Complement activation generates fragments like C3a and C5a, which act as chemoattractants, attracting immune cells to the site of inflammation. These fragments also promote the release of histamine by mast cells and increase the permeability of endothelial cells, contributing to the inflammatory response.
110
● Pathways of Complement Activation: (3)
Classical Pathway
Lectin Pathway
Alternative Pathway
111
What is the classical Pathway?
✔ This pathway is initiated by the binding of antibodies (IgG or IgM) or C-reactive protein (CRP) to the surface of a microbe.
112
What is the lectin pathway?
✔ This pathway is activated when mannose-binding lectin (MBL) binds to
mannose present on the surface of microbes.
113
What is the process of activating of the classical pathway? (4)
114
What is the process of activating of the Lectin Pathway? (5)
115
What is the process of activating of the Lectin Pathway? (5)
116
What is the Alternative Pathway?
✔ In the alternative pathway, complement activation occurs spontaneously at a low level.
117
What is the process of activating the alternative pathway? (7)
118
What are Complement receptors?
● Complement receptors are proteins expressed on the surface of various immune cells and endothelial cells that interact with complement components.
119
● Different types of complement receptors and their functions: (3)
Macrophages and Neutrophils
Mast Cells
Endothelial Cells
120
How do complement receptors function in Macrophages and Neutrophils? (2)
✔ Macrophages and neutrophils express receptors for C3b, allowing them to recognize and phagocytose pathogens that are coated with C3b.
✔ This process enhances the clearance of microbes by these phagocytic cells.
121
How do complement receptors function in Mast Cells? (3)
✔ Mast cells have receptors for C3a and C5a, which are complement fragments generated during complement activation.
✔ When C3a or C5a binds to mast cell receptors, it triggers the release of histamine and other inflammatory mediators.
✔ This leads to inflammation, characterized by increased vasodilation, increased vascular permeability, and the recruitment of immune cells.
122
How do complement receptors function in Mast Cells? (3)
✔ Mast cells have receptors for C3a and C5a, which are complement fragments generated during complement activation.
✔ When C3a or C5a binds to mast cell receptors, it triggers the release of histamine and other inflammatory mediators.
✔ This leads to inflammation, characterized by increased vasodilation, increased vascular permeability, and the recruitment of immune cells.
123
How do complement receptors function in Endothelial Cells? (2)
✔ Endothelial cells, which line the blood vessels, express receptors for C3a and C5a. Binding of these complement fragments to endothelial cell receptors induces increased permeability of the endothelial barrier.
✔ This allows the passage of immune cells and complement components from the blood vessels to the site of inflammation.
124
How do complement receptors function in Endothelial Cells? (2)
✔ Endothelial cells, which line the blood vessels, express receptors for C3a and C5a. Binding of these complement fragments to endothelial cell receptors induces increased permeability of the endothelial barrier.
✔ This allows the passage of immune cells and complement components from the blood vessels to the site of inflammation.
125
Inhibition of Complement:
● To prevent complement activation on their own surfaces, body cells possess various mechanisms of complement inhibition: (2)
Enzymatic degradation
Inhibition of C3 convertase formation
126
● To prevent complement activation on their own surfaces, body cells possess various mechanisms of complement inhibition:
Enzymatic degradation
Body cells express enzymes, such as decay-accelerating factor (DAF) and factor H, which can cleave and inactivate C3b, preventing its further action in the complement cascade.
127
● To prevent complement activation on their own surfaces, body cells possess various mechanisms of complement inhibition:
Inhibition of C3 convertase formation
Body cells also produce proteins, such as CD59, that inhibit the assembly or formation of C3 convertases, preventing the amplification of the complement cascade and subsequent complement-mediated damage.
128
● To prevent complement activation on their own surfaces, body cells possess various mechanisms of complement inhibition:
Inhibition of C3 convertase formation
Body cells also produce proteins, such as CD59, that inhibit the assembly or formation of C3 convertases, preventing the amplification of the complement cascade and subsequent complement-mediated damage.
129
● The adaptive immune system is a specialized defense mechanism in the body that responds to specific antigens, which are foreign substances such as ________ or ________.
● It involves the activation and response of _________, particularly B cells and T cells, as well as the production of antibodies.
pathogens or toxins
lymphocytes
130
How does B cell development begin? (4)
131
How does B cell development begin? (4)
132
5. The heavy chain gene segment locus of the BCR undergoes a process called ___ _________.
VDJ recombination.
133
What does VDJ recombination involve? (2)
✔ This involves the attachment of a variable (V) gene segment to a diversity (D) gene segment, which is then attached to a joining (J) gene segment.
✔ Nucleotides are added between the segments, creating junctional diversity.
134
WHat happens to the heavy chain gene segment after VDJ recombination?
The variable region is then attached to the first constant region(μ), forming the heavy chain gene of the BCR.
135
What happens to the light chain of the BCR?
136
What happens to the light chain of the BCR?
137
FINAL step of BCR:
8. The mature, but naïve, B cell leaves the bone marrow with its unique BCR.
✔ If the BCR cannot be properly made, the B cell dies.
✔ If the BCR binds to ___-_______ in the bone marrow, a process called negative selection occurs, signaling the B cell to undergo apoptosis (cell death).
✔ This helps ______ B cells that could potentially attack the body's own tissues.
self-antigens
eliminate
