Animal: Lecture 7 Flashcards
What is innate immunity?
Innate immunity is something that all animals have.
- Involves the recognition of traits shared by broad ranges of pathogens or bacteria using a small set of receptors to recognize it.
- Rapid response: almost immediate
What is adaptive immunity?
Adaptive immunity is something only vertebrates (animals with a backbone) have.
- Recognition of traits specific to particular pathogens or bacteria, using a vast array of receptors to find a lock and key to this pathogen (very direct)
- It is a slower response but more directed.
What are the types of innate immunity?
- Barrier defenses
- Internal defences
Barrier defences?
skin, mucus membranes, and secretions
Internal defenses?
phagocytic cells, natural killer cells, antimicrobial proteins, and the inflammatory response
What are the types of adaptive immunity?
- Humoral response
- Cell-mediated response
Humoral response?
About bodily fluids. Antibodies defend against infection in bodily fluids
Cell-mediated response?
Works with cells that are already infected. Cytotoxic cells defend against infection in body cells.
What do barrier defenses do?
Barrier defenses prevent most
pathogens from entering the body
Skin/Shells/Cuticle
– Thickened outer surface inhibits entry by pathogens
Mucous membranes
– Mucus secreted by internalized external surfaces traps microbes and other particles
- Internalized surfaces include in the mouth and nose (mucus refers to snot)
Secretions – saliva, tears
– Washing action prevents microbial colonization
– Hostile chemical environment: Lysozyme, acidic pH
- Growth of pathogens is prevented and we flush them out to avoid them colonizing.
Internal defense: Phagocytic cells?
Recognize molecules characteristic of a set of pathogens.
- recognizes that an object is foreign and does not belong.
That recognized molecule is absent from vertebrates and is an essential component of certain groups of pathogens.
- That is, without the essential component, the pathogen would not survive.
Why is it important for the component to be essential to the pathogen?
- The pathogen might end up going hidden if the vital component goes unnoticed - it could still be able to evolve.
What do phagocytic cells do and where are they located?
They destroy pathogens by phagocytosis (eating other cells).
They are located in:
- Blood
- Skin
- Mucous membranes
- Lymph
Examples: neutrophils and macrophages
Process of phagocytosis?
- Pathogen is located by the cell
- The pathogen is engulfed into a vacuole (separated in a bubble)
- A lysosome containing digestive enzymes fuss with the vacuole containing the pathogen
- The pathogen is digested
- The waste is released
Lymphatic system?
The role of our lymphatic system is to maintain our immune system.C
Capillaries and lymphatic vessels?
Very connected with the circulatory (capillary) system (allows a farther reach).
Lymph nodes?
Lymph nodes become swollen/inflammed when fighting an infection.
They house many defensive cells for our immunity: like macrophages and other defensive cells.
- When an infection comes, they are released to help.
Lymphatic system - issue?
Lymphatic system is very closely associated with the circulatory system and the immune system.
- When we have an issue, defensive cells have to travel from nodes, via the lymphatic vessels.
Lipid digestion?
Lipids are diverted to lymph as molecules are too large and need to be broken down by lymph first.
Role of lymph system?
It will bring back leaked fluid into the circulatory system when blood leaks onto other tissues.
- It returns the clean blood to the circulatory system
- Leaked fluid
- Gathered by lymph node
- Checks for pathogens
- Returns to the circulatory system.
Internal defence - natural killer cells?
Natural killer cells are a kinds of lymphocyte (white blood cell in lymphatic system)
Recognize surface proteins of virus-infected or cancerous cells. The result of recognition is the release of chemicals that cause apoptosis (cell death) in infected or cancerous cells
Internal defence - antimicrobial proteins?
They attack pathogens or impede their reproduction. Therefore, they prevent bacteria/viruses from ever dividing.
Interferons?
Proteins secreted by virus-infected cells.
- They trigger surrounding cells to produce chemicals that inhibit viral reproduction
- Therefore, they prevent further reproduction and infection spread
Complement Proteins?
Are plasma proteins activated by substances on the surface
of many microbes
– Lead to lysis of invading cells
– Also involved in inflammation and in adaptive immunity
- When they are activated they come together and form a structure which embeds itself into the membrane forming a tube, allowing fluid and salts through. Therefore, the cell bursts open (lysis).
Internal defence - inflammatory response?
Signalling molecules are released by injured or (flu) infected tissue causing local inflammation (sore throat or redness).
Histamine?
– Triggers vasodilation and increased blood vessel permeability (they have a larger area) in affected area (brings blood to the surface of the body)
– More white blood cells and proteins can enter interstitial fluid as a result. (bringing more blood means there is more redness).
Cytokines?
They are secreted by white blood cells, and further increase blood flow to the affected. This, as a result, brings in more white blood cells.
Process of the inflammatory response?
- Signalling molecules cause capillaries to dilate (e.g., histamines) and increase blood flow (e.g., cytokines)
- The phagocytic cells (e.g., neutrophils), activated complement
proteins, and other antimicrobial proteins arriving from the blood
work together to fight the infection
3 steps of inflammatory response?
- At the injury site, mast cells release histamines, and macrophages secrete cytokines. These signalling molecules cause nearby capillaries to dilate.
- Capillaries widen and become more permeable, allowing fluid containing antimicrobial peptides to enter the tissue. Signals released by immune cells attract neutrophils.
- Neutrophils digest pathogens and cell debris at the site and the tissue heals.
Systemic inflammatory response?
A serious (flu) infection can cause a systemic inflammatory response (e.g., fever)
– Release more white blood cells from the bone marrow (where all wbc
are made)
– Reset body’s thermostat to cause fever
- Fever induces phagocytosis, some enzymes become active with heat and others make more white blood cells.
Histamine increases local blood flow. This leads to the arrival of blood cells that release cytokines that promote local blood flow.
A. This is an example of negative feedback
B. This is an example of positive feedback
B. This is an example of positive feedback.
Adaptive immunity evolves?
Adaptive immunity involves pathogen-specific recognition
How is specificity achieved?
Specificity is achieved through interactions between antigens and antigen receptors?
Antigens?
Antigens are large molecules
found on the surface of specific
pathogens or secreted by those
pathogens
Antigen receptors?
Antigen receptors are proteins
produced by B cells or T cells, and bind to antigens like a “lock and key”. B and T call are a type of lymphatic cell and they are site specific.
Antigens contain…?
Antigens contain multiple epitopes.
Epitopes?
An epitope is a small, accessible portion of an antigen that binds to an antigen receptor
- epitopes allow antigen receptor of B cell to bind to it.
An immune system that is able to recognize multiple epitopes of a single antigen molecule is advantageous because…
A. Some of the epitopes do not trigger an immune response
B. It is less likely that multiple epitopes will mutate than it is that one epitope will mutate
C. Some of the epitopes are hidden inside the pathogen
B. It is less likely that multiple epitopes will mutate than it is that one epitope will mutate.
- One type of B or T cells that can recognize something in a group. of them.
B and T cells are…?
B and T cells are lymphocytes.
Lymphocytes?
Lymphocytes are white blood cells;
produced in the bone marrow
– B cells mature in the bone marrow
– T cells migrate to the thymus for
maturation
Each B or T cell produces?
Each B or T cell produces a single type of antigen receptor.
- Variety = better chance of fighting
- Variety of antigen receptors for a variety of potential epitopes on virus/bacteria.
Each antigen receptor?
Each antigen receptor binds to a single epitope of a single antigen.
Variable regions?
Variable regions of antigen receptors produce the specificity of the antigen-binding site.
- Creates specific binding site for epitope
- Vary from one cell to another
- Variable regions allow multiple epitopes to be recognized
Humoral response?
Humoral Response: B cell antigen
receptors bind to intact antigens in
the blood or lymph
- These antigens may be on the surface of pathogens or may be free antigens secreted by pathogens.
- B cells: bind things that are not supposed to be in blood - lymph fluid.
Cell-mediated response?
Cell-Mediated Response: T cell antigen receptors can only bind to antigen fragments presented on the surface of host cells.
- MHC molecule is attached to the antigen fragment to display it like a tag!
- The T cell antigen receptor is able to connect to the antigen fragment.
B and T cells do what when they encounter epitope?
B cells and T cells proliferate when
they encounter their specific epitope
- Hopefully they will be able to find and fight more of the viruses that are floating around or invade infected cells.
- Proliferate = they divide when they connect the epitope.
What kind of cells are there?
Effector cells and memory cells.
Effector cells?
Effector cells
* Short-lived cells that take effect
immediately against the pathogen or antigen
Memory cells?
Memory cells
* Long-lived cells that give rise to effector cells if the same epitope is encountered again
* When we do blood work, we can tell if an infection has been present before because of the memory cells.
Effector forms of B cells?
Effector forms of B cells are plasma
cells, which secrete antibodies
- Antibodies are soluble forms of the antigen receptor; specific for the same epitope as the original B cell
- Antibodies are released from the plasma cells, then they float around the blood system.
Antibodies?
Antibodies mark pathogens for inactivation or destruction:
- Neutralization prevents pathogen entry into cells
- Toxins can also be neutralized by antibodies.
Antibody binding?
Antibody binding to sites on the pathogen increases the ability of phagocytic cells to recognize the pathogens.
- This leads to increased phagocytosis of pathogens!
- The macrophage or neutrophil has an increased ability to recognize things as foreign objects.
Antibodies activate?
Antibodies activate the complement system, leading to the formation of pores.
- Formation of membrane attack complex allows the flow of water and ions, leading to pathogens lysing and bursting.
Effector forms of T cells are..?
Effector forms of T cells are helper T cells and cytotoxic T cells.
- Cytokines from helper T cells help activate B cells and cytotoxic T cells
- Cytotoxic T cells secrete proteins that lead to cell death in infected cells.
- Helper T cells help activate B cells and cytotoxic T cells.
Cytotoxic T cells?
Cytotoxic T cells bind to infected cells and secrete perforin & granzymes. This ensures that apoptosis is initiated, therefore no more virus is being spread.
Perforin?
Perforin causes pores to form in the cell membrane of infected cells (burst and die)
Granzymes?
initiate apoptosis (cell death)
Memory cell responsibility?
Memory cells are responsible for long-term protection provided by a prior infection or vaccination.
-Memory cells, produced during the original B cell or T cell proliferation, give rise to effector cells if the
same epitope is encountered again
– Secondary immune response ➔ rapid
Primary vs. Secondary response?
- Primary immune response to antigen A produces antibodies to A.
- Secondary immune response to
antigen A produces antibodies to A;
primary immune response to antigen
B produces antibodies to B.
