Week 11 Flashcards
What percentage of deaths worldwide are estimated by WHO to be due to infectious diseases?
23%
This statistic highlights the significant impact of infectious diseases on global mortality.
What is the primary role of the lymphatic system?
Captures lost fluid from the blood, transports dietary lipids, transports foreign substances & immune cells
The lymphatic system plays a crucial role in maintaining fluid balance and supporting the immune system.
What fluid is referred to as lymph when in the lymphatic system?
Interstitial fluid
Interstitial fluid becomes lymph once it enters the lymphatic vessels.
What are the two main divisions of the immune system?
- Innate
- Adaptive
These divisions work together to protect the body from pathogens.
What characterizes the innate immune system?
Present at birth, provides immediate protection, is general
The innate immune system offers non-specific defense mechanisms against a wide range of pathogens.
What is a key feature of the adaptive immune system?
Develops in response to pathogens, has memory, responds more rapidly and tailored on second exposure
The adaptive immune system is highly specific and improves its response upon subsequent encounters with the same pathogen.
List the main types of cells involved in the immune system.
- Neutrophils
- Eosinophils
- Basophils
- Mast cells
- Lymphocytes (B cells & T cells)
- Macrophages
- Dendritic cells
- Natural Killer cells
Each of these cell types has unique functions in immune response.
What is the role of neutrophils in the immune system?
Most abundant phagocytes, first cell at site of infection, major defense against bacteria
Neutrophils are critical for the initial response to infection.
True or False: Eosinophils play a major role in inflammation.
True
Eosinophils are involved in the immune response to parasites and also contribute to inflammatory processes.
Fill in the blank: The lymphatic vessels collect lymph and empty into the _______.
venous system
This drainage is essential for returning fluid to the bloodstream.
What attracts neutrophils to the site of infection?
Chemical gradients (chemotactic)
This process helps ensure that immune cells are directed to where they are needed most.
What do the granules of basophils contain?
- Histamine
- Digestive enzymes
- Heparin
These substances are important in inflammatory responses and allergic reactions.
What are macrophages?
Large agranular cells derived from monocytes that are actively phagocytic
Macrophages deploy a variety of weapons including lysozymes and play a large role in both innate and adaptive immunity.
What is the primary function of dendritic cells?
To present antigens to T cells in lymph nodes after migrating from epithelium and organs
Dendritic cells are a major link between innate and adaptive immunity.
What are natural killer (NK) cells?
Small population of large granular lymphocytes that are cytotoxic against cancer and virally-infected cells
NK cells lack specific antigen receptors and release perforins and granzymes to initiate cell death via apoptosis.
Where do lymphocytes of adaptive immunity mature?
In the bone marrow and thymus
They are able to recognize specific antigens.
What are the two classes of T cells?
- Helper T cells (CD4)
- Killer T cells (CD8)
Each class performs different roles in the immune response.
What is the role of B cells in the immune response?
Produce immunoglobulin and are responsible for the humoral response
B cells differentiate into plasma cells that produce large amounts of antibodies.
What is unique about T cell receptors?
Each T cell expresses a unique antigen-specific receptor
T cells perform effector and regulatory roles in the immune response.
What is lymphoid tissue composed of?
Elements containing vast numbers of immune cells, mostly made of reticular connective tissue
The passage of lymph carries foreign particles to immune cells.
What are the primary lymphatic organs?
- Bone marrow
- Thymus
- Secondary lymph nodes
- Spleen
- Mucosa-associated lymphoid tissue (MALT)
These organs are where lymphocytes mature and activate.
What happens to the thymus after puberty?
It atrophies
The thymus is essential for T cell maturation during early development.
Fill in the blank: Macrophages are a component of _______ immunity but play a large role in _______ immunity.
innate; adaptive
This highlights the dual role of macrophages in the immune system.
What are the two major functions of lymph nodes?
Filtration and immune activation
Where do lymphocytes encounter B cells and dendritic cells in the lymph node?
Cortex
What is contained in the inner cortex of lymph nodes?
Circulating T cells
What are the two main components of the spleen?
Red pulp and white pulp
What is the function of the red pulp in the spleen?
Contains vascular sinuses filled with WBC and macrophages
What is the role of white pulp in the spleen?
Site of lymphatic proliferation and immune surveillance
What are the functions of lymphoid tissue in MALT?
Found in mucous membranes throughout the body
Name three types of tonsils.
- Palatine
- Lingual
- Pharyngeal
Where are Peyer’s patches located?
Wall of the small intestine
What is the first line of defense in the innate immune system?
Physical barriers, cellular constituents, and chemical constituents
List four examples of physical barriers in the innate immune system.
- Skin
- Mucous membranes
- Peristalsis
- Normal microbiota
What is the role of mucous in the immune system?
Secretion of mucous and various antibacterial substances
What are the components of cellular defense in the immune system?
- Phagocytosis
- Neutrophils
- Macrophages
- Natural killer cells
What are the three main stages of inflammation?
- Vasodilation and increased permeability
- Accumulation of phagocytes and antimicrobial proteins
- Clearance of pathogens and accelerated tissue repair
What are examples of chemical defenses in the immune system?
- Inflammation
- Antimicrobial proteins (interferons, complement)
- Fever
True or False: Normal microbiota can inhibit pathogen colonization.
True
How does normal microbiota inhibit pathogens?
- Formation of bacterial layer
- Competing for nutrients and space
- Production of bactericides
What are the symptoms of inflammation?
- Pain
- Redness
- Heat
- Swelling
Fill in the blank: The epidermis acts as a _______ barrier.
Renewable mechanical
What are the components of the dermis and hypodermis in terms of immune function?
- Sweat glands
- Secretions of various antibacterial chemicals
What is leukocytosis?
An increase in the number of white blood cells (WBCs) due to factors released by injured cells.
Leukocytosis is a response to injury or infection, indicating an immune response.
Define margination in the context of phagocytes.
The expression of cell adhesion molecules that enables phagocytes to adhere to capillary walls.
This process is crucial for the migration of phagocytes to sites of injury.
What is diapedesis?
The process by which phagocytes pass through capillary walls into injured tissue.
Diapedesis allows immune cells to reach and infiltrate areas of infection or injury.
What does chemotaxis refer to?
The attraction of cells to the site of injury along chemical gradients.
This process guides immune cells to areas where they are needed most.
List the types of chemical mediators involved in the immune response.
- Proteins/enzyme cascades (Kinins, complements)
- Lipid-derived mediators (prostaglandins, leukotrienes)
- Vasoactive amines (histamine released by mast cells/basophils)
- Cytokines (signaling proteins)
These mediators play significant roles in inflammation and immune responses.
What are antimicrobial proteins?
A collection of cellular and plasma proteins that enhance immunity.
They include key components like interferons and complement proteins.
What are the types of interferons and their main property?
Types:
* Type I → IFNα
* Type II → IFNγ
* Type III → IFNλ
Main property: Anti-viral properties and ability to protect neighboring cells.
Interferons also help regulate inflammation and activate natural killer (NK) cells.
Describe the complement system.
A collection of 20 plasma proteins present in inactive states that enhance inflammation, phagocytosis, and directly kill bacteria when activated.
The complement system is vital for both innate and adaptive immunity.
What are the three pathways of complement activation?
- Classical
- Mannose-binding lectin (MBL)
- Alternative
All pathways lead to the cleavage of C3 into C3a and C3b, which are essential for complement functions.
What initiates the classical pathway of complement activation?
The binding of antibody to antigen and activation of C1.
This pathway is part of the adaptive immune response.
How is the MBL pathway activated?
By lectin binding to mannose on the surface of microbial organisms.
This pathway is crucial for recognizing and responding to certain pathogens.
What is the role of C3a and C5a in the complement system?
- C3a enhances inflammation
- C5a enhances inflammation and promotes phagocytosis
These components are key mediators of the inflammatory response.
What complex is formed by C5b and other proteins in the complement system?
Membrane attack complex (MAC) with C6, C7, C8, and C9.
The MAC is essential for directly killing bacteria by creating pores in their membranes.
What is the function of Lysozyme?
Degrades peptidoglycan in bacterial cell walls
Lysozyme is an antimicrobial protein that plays a role in the innate immune system.
What do various peptides do in the context of antimicrobial activity?
Disrupt microbial membranes and inhibit protein synthesis
These peptides serve as a defense mechanism against microbial infections.
What are the two divisions of adaptive immunity?
- Humoral immunity
- Cellular immunity
Humoral immunity involves antibodies, while cellular immunity involves T cells.
What is the main function of humoral immunity?
Immune function performed by the release of immunoglobulin
It primarily blocks the entry of pathogens for destruction.
What is cellular immunity responsible for?
Causes death of infected cells and pathogens within
This is achieved through the action of T cells.
Define ‘antigen’.
Toxin or foreign substance which induces an immune response
Antigens are crucial for the activation of the adaptive immune system.
What does specificity refer to in the context of antigens?
Ability to bind one but not another member of a family of related substances
This property is essential for the immune system’s precision in targeting pathogens.
Where can antigens be found?
- On foreign cells
- On our own cells
Antigens can be present on both pathogens and the body’s own cells, which is vital for immune recognition.
What characterizes large, complex proteins as antigens?
Possess numerous antigenic determinants
These determinants enhance the likelihood of inducing a strong immune response.
Why are smaller antigens often not very effective at inducing an immune response?
They have a single or very few determinants
Limited antigenic determinants reduce their ability to activate the immune system.
What type of antigens do T cells recognize?
Peptide sequences
This specificity is crucial for T cell activation and subsequent immune response.
How many receptors does each individual cell have for a specific antigen?
Thousands of receptors
All receptors on a single cell are the same, allowing it to recognize only one antigen.
True or False: Each individual cell can recognize multiple antigens.
False
Each individual cell recognizes only one specific antigen due to its unique receptors.
What is immunocompetence?
The ability of lymphocytes to recognize and respond to a large number of foreign antigens while not responding to normal self antigens.
The body can respond to 10^6 - 10^10 different foreign antigens.
Where do lymphocytes develop immunocompetence?
In the primary lymphoid organs: bone marrow for B cells and thymus for T cells.
After development, they circulate in secondary lymphoid organs.
What is the role of MHC molecules?
MHC molecules incorporate and present antigens to T cells as peptide complexes.
There are two distinct types: MHC Class I and MHC Class II.
What types of cells display MHC Class I molecules?
All nucleated cells.
MHC Class I incorporates foreign peptides generated within the cell and presents them to CD8+ T cells.
What are professional antigen presenting cells (APCs)?
Cells that display MHC Class II molecules, including dendritic cells, macrophages, and B cells.
They engulf and break down antigens into peptides.
What is the function of CD4+ T helper cells?
They perform a variety of functions in the immune response.
They interact with antigens presented by MHC Class II molecules.
What are B cell receptors?
Membrane-bound immunoglobulin (antibodies) on B cells.
They are crucial for antigen binding and activation of B cells.
What is the activation process of B cells?
A three-step process: 1) Antigen binds to B cell receptor, 2) Activation, 3) Proliferation and differentiation.
Activated B cells divide into clones.
What are the two distinct types of cells B cells differentiate into after activation?
- Plasma cells
- Memory B cells
What do plasma cells do?
They secrete large quantities of immunoglobulin (antibodies).
Plasma cells secrete about 2000 antibodies per second and live for approximately 4-5 days.
What is the role of memory B cells?
They remember the antigen for future activation.
This allows for a tailored antibody response to the pathogen upon re-exposure.
What are antibodies also known as?
Immunoglobulins.
They consist of two identical light chains and two heavy chains.
What determines the class (isotype) of an antibody?
Heavy chains
Heavy chains are linked to each other and a light chain by disulphide bonds.
What are the two regions of an antibody?
Variable region and constant region
The variable region binds to the antigen and is specific for one antigen, while the constant region dictates the characteristics of the antibody.
What is the function of the variable region in antibodies?
Binds to antigen
There are two variable regions on each antibody, specific for one antigen.
What process do T cells undergo to recognize antigens?
Clonal selection
T cells recognize antigens via the T cell receptor (TCR).
What do T cells recognize that is bound to MHC molecules?
Peptide
T cells utilize their T cell receptors to recognize peptides presented on MHC molecules.
Which T cells recognize MHC Class II molecules?
CD4 T cells
CD4 T cells help activate other T cells.
What type of T cells recognize MHC Class I molecules?
CD8+ T cells
CD8+ T cells are also known as cytotoxic T cells.
What is the primary function of cytotoxic T cells?
Attack and destroy infected cells
Their main targets are virally-infected cells.
What do cytotoxic T cells release to induce cell death?
Perforin and granzymes
These substances help induce apoptosis in infected cells.
What accessory molecules do helper T cells express?
CD3
CD3 is involved in intracellular signaling.
Fill in the blank: T cells recognize _______ presented on MHC Class I.
peptide
This recognition is crucial for the activation and function of cytotoxic T cells.
