W11 The immune system Flashcards
inc lec: the lymphatic system and the immune system Innate immune system and adaptive immune system- antigen recognition
What are Immunogens?
They trigger the body’s immune response.
What is the definition of immunity?
Ability to resist damage from pathogens, toxins and internal threats
What does the immune system consist of?
- Lymphoid tissues / Lymphatic System
- Immune cells
- Chemicals that coordinate and carry out immune functions
- “self ” from “non-self” - a targeted response
What are the functions of the immune system?
What are the 2 types of response?
- Recognize and remove abnormal “self ” cells
- Removes dead or damaged cells
- Protects the body from disease-causing invaders
- Bacteria, viruses, fungi, protozoans (one cell), parasites
- Pollens, chemicals, and foreign bodies
- Immunogens: trigger the body’s immune response
- Nonspecific Innate Immunity and Specific Acquired Immunity (adaptive)
What is the lymphatic system?
- System of vessels / cells / organs that carries excess fluids to the bloodstream and
filters pathogens from the blood - drain body fluids and return them to the bloodstream
What is lymph?
Interstitial fluid (fluid that fills spaces between cells) once it has entered the lymphatic system
What is lymph?
Interstitial fluid (fluid that fills spaces between cells) once it has entered the lymphatic system
What are the functions of the lymphatic system?
- Fluid Balance
-Lipid Absorption - Defence against pathogens
- Pathogen
- Substance or microorganism that causes disease or damage to the tissues of the body
- use humans as a source of nutrients and as an environment to survive in
Lymphatic System and Drainage
- Tonsils, the lymph nodes, the spleen, the thymus
- Lymph nodes -located along lymphatic vessels
- Groups in the cervical (neck), axillary (armpit), and inguinal (groin) areas
- Lymph: Carries fluid from tissues to circulatory system
- Vessels begin as open-ended capillaries,
- Feed into larger lymphatic vessels
- Empty into the bloodstream by ducts. –
- Lymph travels through the lymph nodes
- Doesn’t circulate ie not pumped by heart
- Forced through the vessels by contraction of skeletal muscles -
Valves, (one way semi lunar valves)
* one-way flow of lymph
Lymphatic System: Capillaries
- Where fluid enters the lymphatic system
- In virtually all tissues
- between arterioles and venules
- Thinner walls than veins
- Overlapping epithelial ‘flaps’
- fluid moves into capillaries only
Lymphatic System: small intestine
- Lymphatic capillaries called
lacteals - Lipids and some lipid soluble
proteins and vitamins form milky
fluid = chyle - Enter lacteals
- Enter blood stream
Lymphatics Circulation
- Lymphatic capillaries—- Vessels—-Trunks— 2 ducts
Drainage
* Right: Right lymphatic duct drains into right subclavian vein
* right sides of the head, thorax, and right arm
* Left: Thoracic duct drains into the left subclavian vein
* remaining portions of the body
What are the Lymphatic Organs?
- Tissue: Many lymphocytes / defence cells
- Lymphocytes: Red bone marrow
- Tonsils
- Palatine tonsils
- Pharyngeal tonsils (adenoids when enlarged)
- Lingual tonsil
- Protective ring of lymphatic tissue around the nasal and oral cavities and the pharynx
- Pathogens
Where do you find red bone marrow cells?
Skull
Spongy bone at the end of compact bone
Lymph node
- Distributed along the lymphatic vessels
- Lymph passes through before entering blood
- Superficial or deep
- Superficial aggregations
- (1) inguinal nodes in the groin, (2) the axillary nodes in the axilla (armpit), and (3) the cervical nodes in the neck.
- Dense capsule with extensions: trabeculae
- lymphatic tissue: Lymphocytes and lymphatic nodules
- lymphatic sinuses: macrophages- phagocytosis (engulfing bacteria)
- Lymph flows through nodes
- Activates – stimulating
lymphocytes to divide - Nodules: germinal centres
- Remove pathogens: macrophages
What is the function of the spleen?
What are the components of it?
Filters blood- Respond to foreign substances, destroy old RBC
White pulp
* Composed mainly of lymphocytes
* Lymphatic tissue surrounding arteries
* Lymphocytes can be stimulated to divide
Red pulp
*Associated with extensive blood vessels and venous sinuses
* Surrounding veins
* Macrophages and red blood cells
* Macrophages remove foreign substances and worn-out red blood cells through phagocytosis
* Also functions as a blood reservoir
What is the thymus?
- 2 lobed gland
- Divided into lobules
- Cortex (dark)
- Many lymphocytes
- Medulla (light)
- Fewer lymphocytes
- Maturing T-cells
- Mature T-cells migrate to medulla, enter blood and travel to other lymphatic tissue
What is chyle?
Lipids and some lipid soluble proteins and vitamins form a milky fluid
Which of the lymphoid nodes us most likely to see food antigens first?
Tonsils
Bronchus-associated lymphoid tissue
Axilla
GALT
= Tonsils
How is blood returned from the lymphatic system?
Skeletal muscles contract and washes lymphatic vessels
Cells of the Immune System (6)
- Leukocytes: white blood cells (WBCs): Key cells for immune response
- Circulate in the blood but leave and function extra vascular
(1) eosinophils
(2) Basophils (blood); related mast cells (tissues)
(3) neutrophils
(4) monocytes and macrophages
(5) lymphocytes and plasma cells
(6) dendritic cells
(not often found in blood) - Classified: morphologically and functionally
- Phagocytes
- Cytotoxic cells
- APCs
- display fragments of foreign proteins on their cell surface
- formed in the bone marrow and
released into the circulation* (See Prof Mohankumar’s lectures)
How do Basophils and Mast cells contribute to the immune response?
Where are they found?
They Release mediators that contribute to inflammation
* Histamine, heparin (anticoag) and other cytokines
* Allergic and immune response
Basophils- circulation
Mast cells (tissue): lungs, GI tract, skin
How do Eosinophils contribute to the immune response?
- Allergic reactions and parasitic diseases
- Digestive tract, lungs, urinary and genital epithelia, and connective
tissue of the skin - Cytotoxic: release substances from their granules that directly
damage or kill the parasites
What are Neutrophils?
What is their function?
- Phagocytic cells
- most abundant WBC
- segmented nucleus
- Most remain in the blood but can leave if attracted to an
extravascular site of damage or infection - Kill / ingest bacteria
- release a variety of cytokines
- including fever-causing pyrogens
What are Monocytes and Macrophages
- Monocytes precursors of tissue macrophages
- Once in the tissues, monocytes enlarge and differentiate into
phagocytic macrophages - Key scavengers within tissues
- Antigen Presenting Cell (APC)
- Antigens: Immunogens that react with B and T lymphocytes
- APCs can insert fragments of processed antigen into its membrane -
becomes part of surface protein complexes - they can bind to and activate other types of immune cells.
What is the function of Lymphocytes
What are the 3 subtypes?
- Key cells that mediate the acquired immune
response of the body - Most in lymphoid tissue
3 subtypes:
* B Lymphocytes (APCs)
* T lymphocytes
* Natural Killer cells
What are dendritic cells? What is their function
Where are they found?
- Long processes
- Antigen-presenting cells
- Found in skin (Langerhans cells)
- Other organs
- Once capture antigens migrate to lymph nodes
- Present antigens to lymphocytes which activates lymphocytes
Phagocytosis and antigen presentation:
What are they key cells that phagocytose?
What cells present antigens?
How does phagocytosis occur?
Macrophages and Neutrophils key cells that phagocytose
* Some B lymphocytes and dendritic cells also present antigen
- Some pathogens bind directly to phagocyte receptors / others precoated by antibodies
- Stimulates internalisation
- Digests pathogen
- Part of it (antigen) presented on surface
Phagocytosis and antigen presentation
Macrophages and Neutrophils key cells that phagocytose
* Some B lymphocytes and dendritic cells also present antigen
* Some pathogens bind directly to phagocyte receptors / others precoated by antibodies
* Stimulates internalisation
* Digests pathogen
* Part of it (antigen) presented on surface
Which cells are phagocytic?
Macrophages
Which cells degranulate and release chemical mediators?
Lymphocytes
Macrophages
Mast cells
Mast cells
What is Innate immunity?
Response to pathogens same each time the body is exposed
What is Adaptive immunity?
(adaptive immune response)
Characteristics?
- Response to pathogens improves each time the pathogen is encountered.
- Characteristics: Specificity and memory
What is Adaptive immunity
- Response to pathogens improves each time the pathogen is encountered.
- Characteristics: Specificity and memory
Specificity- Recognise a particular substance eg. specific virus or bacteria
Memory- “remembers” previous encounters with a particular substance. - Future responses are faster, stronger, and longer-lasting
What are the 2 systems of immunity?
- innate immunity / nonspecific resistance
- adaptive immunity / specific immunity
A person is said to be immune if..
If the pathogen is destroyed before any symptoms develop
Innate immunity is..
It consists of..
What does it enhance?
- Rapid and non specific
Consists of: - Physical Barriers
- Chemical Mediators
- Leukocytes (WBC)
- Inflammatory Response
- Enhances adaptive immune response
What are physical barriers?
- Skin* Epidermal Keratinized cells
- Sweat and secretions – lower pH
- Mouth / oral cavity* Salivary glands – lysozyme
- Stomach/GI tract* Low pH
- Mucosal epithelia* GI tract
- Respiratory tract
- Ears
- Nose- Traps and removes
- Tears, saliva, and urine wash these substances from body surfaces
Pathogens cannot cause a disease if they cannot get into the body
What do Chemical Mediators do?
They promote the immune response.
* Complement
* > 20 Proteins in plasma
* Normally inactive
* Once activated - series of reactions - each complement protein activates the next.
* Contribute to adaptive and innate systems
* Innate: “alternate pathway” of complement activation
* Bind to the cell membrane of the pathogen labelling it for phagocytosis (opsonization)
* Act as chemotactic agents to attract phagocytic cells to the site of inflammation
* Form damaging pores in the plasma membrane of the pathogen
* Cells swell and lyse (rupture)
Give examples of the main chemical mediators:
Cytokines
Interferons (IFNs)
What are cytokines?
- Small signalling molecules released from cells to trigger immune response
- Egs Interleukins + chemokines + interferons
What are Interferons (IFNs)?
- Viruses:
- Induce cells to produce viral nucleic acids and proteins
- Cells infected with viruses secrete interferons
- Travel to adjacent cells and induce them to make antiviral proteins
- Prevents production of new viral nucleic acids and proteins
- Inhibit viral reproduction in these surrounding cells
- Some IFNs also activate other immune cells (macrophages and NK cells)
What are some other chemical mediators?
- Histamine
- Prostaglandins
- Leukotrienes
Variously
* vasodilation,
* increasing vascular permeability
* stimulating phagocytosis
* Promote inflammation
Innate Immunity: White Blood cells
Where are WBC produced?
Produced in red bone marrow / lymphatic tissue.
* Chemicals released from pathogens or damaged tissues attract WBC
* Leave blood and enter tissue
* Phagocytic cells
* Neutrophils normally first
* Release signals that increase inflammatory response
* Recruits and activates other immune cells
* Pus- dead neutrophils
* Macrophages (monocytes that leave blood)
* Larger - later stages of an infection
* cleaning up dead neutrophils and other cellular debris
Why should you not hold urine for long periods?
Urination flushes out bacteria
Inflammatory cells
- Basophils* Mobile cells
- Mast cells* Non mobile cells in connective tissue
- Eosinophils* Allergic response
- When activated: release histamine and leukotrienes* Inflammatory response
Natural Killer cells
* NK cells recognize classes of cells, eg tumour cells / virus-infected cells
* Kill their target cells* releasing chemicals that damage cell membranes causes the cells to lyse
Inflammatory response; What is vasodilation and what hormones are involved?
What does histamine increase?
Vascular permeability, so increases the blood supply to the area.
* Leakage of fluid into tissue - swelling /oedema
* Allows complement to enter tissue
* Enhances inflammatory response / attracts more phagocytes
* Clotting factors enter (fibringogen- fibrin) –
* Wall off/ first step in wound repair
(Boosts blood flow and H1 receptors)
histamine is a chemical organic compound that your immune system releases
Which cells are responsible for much of the phagocytosis at an EARLY stage of an infection?
Neutrophils
What do Mast cells do?
They are non mobile cells that sit on connective tissue
They detect a pathogen, then degranulate
Which are the 2 main phagocytic cells?
Neutrophils and Macrophages
Which cells are responsible for much of the phagocytosis at a LATER stage of an infection?
Macrophages
Which cells are the most important in the release of histamine which promotes inflammation?
Mast cells
Which of the following signs is not a characteristic of inflammation?
Redness
Pain
Cold
Swelling
Antigen Presenting Cells have which class of MHC molecule?
MHC Class ll
Antigens are…
Foreign substances introduced into the body
Molecules produced by the body
Stimulate an adaptive immune response
The secondary antibody response
a. Is slower than the primary
b. Produces fewer antibodies
c. Is quicker to produce antibodies
C= Is quicker to produce antibodies
What are the functions of Cytoxic T cells ? (2)
Release cytokines:
* Attract innate immune cells
* Macrophages
* Phagocytosis of antigen/cell
* Inflammatory response
* Activate additional cytotoxic T cells
Directly kill virus infected
cells:
* Viral antigens on surface
* T cells bind to the antigens on the surfaces and cause the cells to lyse or under go apoptosis
Allergic response
*Immune response to a non-pathogenic antigen
*Allergen is an antigen that is typically not harmful to the body
*Sensitive individuals : inappropriate immune
response
* Sensitivity / hypersensitivity to the antigen
*Immediate hypersensitivity reactions are
mediated by antibodies
Sensitisation and Re-exposure Phase
*Sensitization phase
* equivalent to the primary immune response
Aging Immune system
*Little effect on the lymphatic system
* remove fluid from tissues,
* absorb lipids from the digestive tract
* remove defective red blood cells
*Severe impact on the immune system
* thymus replaced with adipose tissue
* lose the ability to produce mature T cells
* May lose functionality
* Antigen exposure leads to fewer helper t cells
* Less stimulation of B and cytotoxic T cells
*Antibody and cell mediated responses decrease
*Primary and secondary antibody responses decrease
