Chapter 22 Flashcards
Immunity
Ability to ward off damage or disease through defences
Susceptibility
Vulnerability or lack of resistance
What are the two general types of immunity?
- Innate
- Adaptive
Innate immunity
Defences that are present at birth
Nonspecific
First line: physical and chemical barriers of skin
Second line: Antimicrobial substances, natural killer cells, phagocytes, inflammation and fever
Adaptive immunity
Specific recognition of microbes once it has breached the innate immunity defences
What does the lymphatic system consist of?
Lymph
Lymphatic vessels
Lymphocytes
Red bone marrow
Lymph
Interstitial fluid that passes into lymphatic vessels
Clear, pale yellow fluid
Lymphatic tissue
Specialized form of reticular connective tissue that contains large number of lymphocytes
Immune responses: B cells and T cells
Three primary functions of the lymphatic system?
- Drains excess interstitial fluid
- Transports dietary lipids
- Carries out immune responses
Lymphatic capillaries
Start of lymphatic vessels
Spaces between cells
Closed at one end
Unite to form larger lymphatic vessels
Greater permeability than blood capillaries
Can absorb proteins and lipids
One way permeability
Lacteals
Specialized lymphatic capillaries in the small intestine carry dietary lipids into the lymphatic vessels and ultimately into the blood
Chyle
Creamy white lymph that drains from the small intestine
What are the lymph trunks following the lymph nodes
- Lumbar
- Intestinal
- Bronchomediastinal
- Subclavian
- Jugular
Lumbar trunks drain lymph from where?
Lower limbs
Wall and viscera of the pelvis
Kidneys
Adrenal glands
Abdominal wall
Intestinal trunk drains lymph from where?
Stomach
Intestine
Pancreas
Spleen
Part of liver
Bronchomediastinal drains lymph from where?
Thoracic wall
Lung
Heart
Subclavian trunks drain lymph from where?
Upper limbs
Jugular trunks drain lymph from where?
Head and neck
Flow of lymph
Blood capillaries
Interstitial spaces
Lymphatic capillaries
Lymphatic vessels
Lymphatic trunk or ducts
Junction of internal
What are the two main pumps that support flow of lymph?
Respiratory pump
skeletal muscle pump
What are the primary lymphatic organs?
where stem cells divide and become immunocompetent including red bone marrow and thymus
What are the secondary lymphatic organs?
Where most immune responses occur including lymph nodes, spleen, lymphatic nodules
Thymus
Pre-T cells migrate from the red bone marrow to the cortex of the thymus where they become T cells consist of enclosed capsules and extensions call trabeculae
Lymph nodes
Contain lymphatic nodules which are egg shaped aggregates of B cells
lymphatic nodules containing mostly B cells are primary lymphatic nodules
lymphatic nodules in the outer cortex are secondary lymphatic nodules
What’s the function of lymph nodes?
Functions is a filter
Spleen
Largest single mass of lymphatic tissue in the body
contains white pulp consisting mostly of lymphocytes and macrophages located around central arteries and
red pulp consisting of blood filled venous sinuses in cords of splenic tissue called splenic cords/bill Rothy’s cord
Lymphatic nodules
Egg shaped masses of lymphatic tissue not surrounded by a capsule scattered around connective tissue of mucous membranes lining G.I., urinary, and reproductive tract also called mucosa associated lymphatic tissue
What are the names for the five tonsils?
1 pharyngeal tonsil
2 palatine tonsils
paired lingual tonsil
Name the chemicals that contribute to the high degree of resistance of the skin and mucous membranes?
Sebum, perspiration, gastric juice
Name the four main types of anti-microbial substances that discouraged microbial growth
Interferons, compliment, iron binding proteins, and antimicrobial proteins
What produces the interferons protein?
Lymphocytes, macrophages, and fibroblast infected with viruses
What is the complement system?
A group of normally inactive proteins in blood plasma and on plasma membranes when activated they enhance certain immune reactions such as Cystolysis of microbes, phagocytosis, and inflammation
Iron binding proteins
Inhibit the growth of certain bacteria by reducing the amount of available iron such as transferrin, lactoferrin, ferritin, and haemoglobin
Antimicrobial proteins
Short peptides that have a broad spectrum of antimicrobial activity and can attract Dendritic and mast cells which participate in immune responses
What are the different ways natural killer cells work?
- Contain a protein called perforin that insert into the plasma of target cells and cause cytolysis
- Release granzymes which cause the target cell to undergo a apoptosis which are then destroyed by Phagocytes
What are the two main types of Phagocytes?
Neutrophils and macrophages
What are the five phases of phagocytosis?
Chemotaxis
adherence
ingestion
digestion
Killing
What are the signs and symptoms associated with inflammation?
Pain due to the release of certain chemicals
Redness because more blood is rushed to the affected area
Immobility that results from some loss of function and severe inflammations
Swelling caused by an accumulation of fluids
Heat which is also due to more blood rush to the affected area
What are the two immediate changes that occur in the blood vessel in a region of tissue injury?
Vasodilation of arterials and increased permeability of Capillary’s
What are the substances that contribute to vasodilation?
Histamine
Kinins
prostaglandins
Leukotrienes
complement
Histamine
Mast cells in connective tissue in Basophils and platelets in blood release histamine
neutrophils and macrophages attracted to the side of injury also stimulates the release of histamine
causing vasodilation and increase permeability
Kinins
Polypeptides formed in blood from inactive precursors called kininogens induce vasodilation and increase permeability and serve as chemotactic agents for Phagocytes
Prostaglandins
Released by damage cells and intensify the effects of histamines and kinins and may also stimulate the immigration of phagocytes through Capillary walls
Leukotrienes
Produced by basophils in mast cells cause increased permeability and function in adherence of Phagocytes to pathogens and chemotactic agents that attract Phagocytes
Complement
Different components of the complement system stimulate histamine release, attract neutrophils by chemo taxis, and promote phagocytosis some components can also destroy bacteria
What are the signs and symptoms of inflammation ?
Heat, redness, swelling
Antigens (Ags)
Substances that are recognized as foreign and provoke immune responses also means antibody generators
What distinguishes adaptive immunity from innate immunity?
- Specificity - Distinguishing self from nonself molecules
- Memory - For most previously encountered antigens so that a second encounter prompts and even more rapid and vigourous response
Immune system
Includes cells and tissues that carry out immune responses
What does adaptive immunity involve?
Lymphocytes called B cells and T cells
Where do B cells develop?
Red bone marrow
Where do T cells develop?
Pre-T cells are developed in the red bone marrow and then fully develop in the thymus
Immunocompetence
Before T and B cells leave the thymus and red bone marrow they develop immunocompetence
the ability to carry out adaptive immune responses
Antigen receptor’s
Molecules capable of recognizing specific antigens
What are the two major types of mature T cells that exit the thymus?
Helper T cells and cytotoxic T cells
Helper T cells are also known as what and what do they do?
CD4 T cells
in addition to antigen receptors there plasma membranes include a protein called CD4
Cytotoxic tea cells are also referred to as what and what do they do?
CD8 T cells because their plasma membranes contain not only antigen receptors but also a protein known as CD8
What are the two types of adaptive immunity?
Cell mediated immunity and antibody mediated immunity
Cell mediated immunity
Cytotoxic T cells directly attack invading antigens
Particularly effective against
1. intracellular pathogens including viruses, bacteria, fungi, that are inside cells
2. some cancer cells and
3. foreign tissue transplants
Antibody mediated immunity
B cells transform into plasma cells which synthesize and secrete specific proteins called antibodies
Antibodies
Also called immunoglobulins
a given antibody combine to and inactivate a specific antigen
What is antibody mediated immunity also known as?
Humoral immunity
What is clonal selection?
The process by which a lymphocyte proliferate (divides) and differentiates ( forms more highly specialized cells) in response to a specific antigen
What is the result of clonal selection?
The formation of a population of identical cells called clone that can recognize the same specific antigen as the original lymphocytes
What are the two main cells that are given rise to after a lymphocyte undergoes clonal selection?
Effector cells and memory cells
Effector cells of a lymphocyte clones?
- Active helper T cells
- Active cytotoxic T cells
- Plasma cells which are part of a bee cell clone
What happens to effector cells after an immune response?
Most of them die other than a memory cells
What are included in memory cells?
- Memory helper T cells
- Memory cytotoxic T cells
- Memory B cells
What are the two important characteristics of antigens?
Immunogenicity and reactivity
Immunogenicity
The ability to provoke an immune response by stimulating the production of specific antibodies, the proliferation of specific T cells or both
Antigen
Antibody generator
Reactivity
The ability of the antigen to react specifically with the antibodies or cells it provoked
Complete antigens
Substances with both immunogenicity and reactivity
Epitopes
Small parts of a large antigen molecule that acts as a trigger for immune responses
Also called antigenic determinants
What are the three routes that Antegens take when they get past the Innate defenses?
- Most antigens that enter the bloodstream are trapped as they flow through the spleen
- Antigens that penetrate the skin enter lymphatic vessels and lodge in the lymph nodes
- Antigens that penetrate mucous membranes are trapped by mucosa associated lymphatic tissue
Hapten
A smaller substance that has reactivity but lacks immunogenicity
Can stimulate an immune response only if it is attached to a larger carrier molecule
Genetic recombination
The diversity of antigen receptors in both B cells and T cells is the result of shuffling and rearranging of a few hundred versions of several small Gene segments
Major histocompatibility complex (MHC) antigens
Located in the plasma membrane of body cells are “self antigens”
trans member glycoproteins
can also be called human leucocyte antigens
these antigens are unique
function in tissue rejection from transplants and to help T cells recognize that an antigen is foreign
Antigen processing
Antigenic proteins are broken down into peptide fragments that then associate with MHC molecules
next the antigen MHC complex is inserted into the plasma membrane of a body cell
Antigen presentation
The insertion of the complex into the plasma membrane
If the peptide fragment comes from a self protein, T cells ignore the antigen
If the peptide fragment comes from a foreign protein, T cells recognize the antigen as an intruder and an immune response takes place
Exogenous antigens
Foreign antigens that are present in fluid outside body cells
Such as bacteria, bacterial toxins, parasitic worms, inhaled pollen, and dust and viruses that have not yet infected a body cell
Antigen presenting cells (APCs)
Process and present exogenous antigens
Include dendritic cells, macrophages, and B cells
Located in epidermidis and dermis of the skin, mucous membranes that line the respiratory, gastrointestinal, urinary, and reproductive tracts and lymph nodes
What are the steps in the processing and presenting of an exogenous antigen by an antigen-presenting cell?
- Ingestion of the antigen
- Digestion of antigen into peptide fragments
- Synthesis of MHC – two molecules
- Packaging of MHC – two molecules
- Fusion of vesicles
- Finding of peptide fragments to MHC–2 molecules
- Insertion of antigen-MHC – two complexes into the plasma membrane
Endogenous antigens
Foreign antigens that are present inside body cells
Can be viral proteins produced after virus infects the cell and takes over the cells metabolic machinery, toxins produced from intercellular bacteria, or abnormal protein synthesized by cancer cell
The steps in the processing and presenting of an Endogenous antigen by an infected body cell occurs how?
- Digestion of an antigen into peptide fragments
- Synthesis of MHC – one molecules
- Binding of peptide fragments to MHC –1 molecules
- Packaging of antigen – MHC –1 molecules
- Insertion of antigen – MHC – one complexes into the plasma membrane
Cytokines
Small protein hormones that stimulate or inhibit many normal cell functions such as cell growth and differentiation
Secreted by lymphocytes and antigen presenting cells as well as fibroblasts, endothelial cells, monocytes, hepatocytes, and kidney cells
How does cell mediated immune responses begin?
With activation of a small number of T cells by a specific antigen
T cell receptors (TCRs)
Recognize and bind to specific foreign antigen fragments that are presented in Antigen MHC complexes
Costimulation
When a T cell becomes activated only if it binds to the foreign antigen and at the same time receives a second signal
Interleukin – 2 (IL-2)
A cytokin costimulator
Anergy
A prolonged state of inactivity, happens without Costimulation
Helper T cells
CD4 T cells
Recognize exogenous antigen fragments associated with major histocompatibility complex class two molecules at the surface of an APC
CD4 protein and a APC interact with each other costimulation occurs and the helper T cell becomes activated
Active helper T cells
Start secreting a variety of cytokines after costimulation such as interleukin-2 which is needed for virtually all immune responses and is the prime trigger of T cell proliferation
Cytotoxic T cells
CD8 T cells
Recognize foreign antigens combined with major histocompatibility complex class 1 molecules on the surface of
1. body cells infected by microbes some
2. tumour cells and
3. cells of a tissue transplant
Active cytotoxic T cells
Attack other body cells that have been infected with the antigen
Memory cytotoxic T cells
Do not attack infected body cells
Can quickly proliferate and differentiate into more active cytotoxic T cells and more memory cytotoxic T cells if the same antigen enters the body at a future time
What are the cytotoxic T cells two principle mechanisms for killing infected target cells?
- Receptors on their surfaces recognize and bind to infected target cells that have microbial antigens displayed on their surface, then release granzymes (protein digesting enzymes that trigger apoptosis) once infected cells are destroyed, the released microbes are killed by phagocytes
- Cytotoxic T cells bind to infected body cells and release two proteins from their granules perforin and granulosum
perforin inserts into the plasma membrane of the target cell and creates channels in the membrane which causes extracellular fluid to flow into the target cell and cytolysis occurs
others release granulysin which enters through the channels and destroys the microbes by creating holes in their plasma membranes
they can also release a toxic molecule called lymphotoxin soon which activates enzymes in the target cell these enzymes cause the target cells DNA to fragment in the cells and die
they also secrete gamma interferon which attracts and activates Phagocytic cells and macrophage migration inhibition factor which prevents migration of Phagocytes from the infection site
after detaching from a target cell a cytotoxic T cell can seek out and destroy another target cell
Tumour antigens
Found on the cell surface of cancerous cells
Immunological surveillance
When the immune system recognizes a tumour antigen as non-self and destroys it
What is the structure of an antibody?
Also called an immunoglobin has:
Heavy (H) trains - Consist of 450 amino acids short carbohydrate chains are attached to each heavy polypeptide
Light (L) chains - Consists of 220 amino acids a disulphide bond holds each light chain too heavy chain to disulphide bonds also link in the middle region of the two heavy chains
Hinge region - link of the chains flexible and called the “arms”
Stem region - beyond the hinge region, formed by parts of the heavy chains
What are actions of antibodies?
- Neutralizing antigen
- Immobilizing bacteria
- Agglutinating and precipitating antigen
- Activating compliment
- Enhancing phagocytosis
Immunoglobin igG characteristic and function?
Accounts for 80% of antibodies
Found in blood, lymph, intestine
Monomer structure
Enhances phagocytosis, neutralizes toxins, triggers complement system
Crosses placenta, allowing immune protection in newborns
Immunoglobin IgAs characteristic and function?
10-15% of antibodies
Found in sweat, tears, saliva, mucus, breast milk, GI secretions, small amounts in blood and lymph
Monomer and dimers
Decrease during stress, lowering resistance to infection
Localized protection to mucous membranes
Immunoglobin IgM characteristics and functions?
5-10% of antibodies in blood
Found in blood and lymph
Pentameters (five)
Secreted by plasma cells after initial antigen exposure
Activated complement and causes agglutination and lysis of microbes
Monomers on surface of Bcells, as antigen receptors, ABO blood group to detect incompatible transfusion’s
IgD characteristics and function
0.2% of antibodies in blood
Surface of B cells
Monomer
Activation of B cells
IgE characteristics and function
.1% of antibodies in blood
Monomers
Located on mast cells, basophils
Involved in allergic and hypersensitivity reactions; protection against parasitic worms
Complement system
Defensive system made up of over 30 proteins produced by the liver and found in blood plasma and within tissue throughout body
Destroy microbes by phagocytosis, cytolysis, and inflammation
Prevent excess damage to body tissues
Activated only when split by enzymes into active fragments
What is C3’s cascade of reactions that bring about phagocytosis, cytolysis, and inflammation?
- Inactivated C3 splits into activated C3a and C3b
- C3b binds to surface of microbes and receptors on phagocytes attach to the C3b. Enhancing phagocytosis by coating a microbe, process called opsinization which promotes attachment of a phagocyte to a microbe
- C3b also initiates a series of reactions that bring about cytolysis, first C3b splits C5. C5b fragment binds to C6 and C7 which attach to plasma membrane of invading microbe. Then C8 and C9 molecules join the other complement proteins to form cylinder shaped membrane attack complex which enters the plasma membrane
- Membrane attack complex creates channels in the plasma membrane resulting in cytolysis
- C3a and C5a Find Thomas cells and caused them to release histamine that increases blood vessel permeability during information C5 a also attracts Phagocytes to the site of inflammation
What are the three ways that C3 can be activated?
- The classical pathway - we’re antibodies bind to antigens
- The alternative pathway - does not involve antibodies it is initiated by an interaction between lipid carbohydrate complexes on the surface of microbes and complement protein factors B, D, P
- Lectin pathway - macrophages that digest microbes release chemicals that cause the liver to produce proteins called lectins, lectin binds to the carbohydrates on the surface of microbes
Immunological memory
Is due to the presence of long lasting antibodies and very long live lymphocytes that arise during clonal selection of antigen stimulated B cells and T cells
Antibody titre
A measure of immunological memory, the amount of antibody and serum
After the initial contact with an antigen how many antibodies are present for the period of several days after?
None
Naturally acquired active immunity
Following exposure to a microbe antigen recognition by B cells and T cells and costimulation lead to the formation of antibody secreting plasma cells, cytotoxic T cells, and B and T memory cells
Naturally acquired passive immunity
IgG antibodies are transferred from mother to fetus across placenta, or IgA antibodies are transferred from mother to baby in milk during breast-feeding
Artificially acquired active immunity
Antigens introduced during vaccination stimulate cell mediated an antibody mediated immune responses leading to the production of memory cells, antigens are pre-treated to be immunogenic but not pathogenic (they will trigger an immune response but not cause significant illness)
Artificially acquired passive immunity
Intravenous injection of immunoglobulins (antibodies)
What are the two traits T cells must have?
- Must be able to recognize own histocompatibility complex (MHC) proteins (self recognition)
- Self-tolerance- lack reactivity to peptide fragments from own proteins
What can loss of self tolerance lead to?
Development of autoimmune diseases
How do pre T cells in the thymus develop the capability for self recognition?
Positive selection
Negative selection
Weeding out process to develop self tolerance
Occurs by deletion - self reactive T cells undergo apoptosis and die and
anergy where they remain alive but are unresponsive to antigenic stimulation
