UNIT 4 - AOS 1 - CH5 Flashcards
Antigen
“Molecules that stimulate the adaptive immune response”
- Can be apart of pathogens or chemicals
Types of antigens
SELF ANTIGENS:
“Not foreign and they are tolerated by immune system”
NON-SELF ANTIGENS:
“Detected as foreign by cell surface receptors (MHC) and attacked by immune system”
Pathogen
“Agents that cause diseases”
Major histocompatibility complex (MHC)
“Receptor proteins on the surface of cells that identify the cells as ‘self’ “.
- Helps immune system distinguish the bodies proteins from proteins made from foreign invaders
MHC-I
- Present on all nucleated cells in body
- Contains site that forms structural binding site for antigen (what allows cells to be recognised as ‘self’, so they won’t be attacked)
MHC-II
- Present on specific immune cell (wbc)
- ‘non-self’ antigens are presented on the MHC-II, helping to initiate the adaptive immune response
(Macrophages & dendritic cells are antigen presenting = present antigens on their MHC-II, which binds to helper T cells & helps activate the adaptive immune response)
Types of pathogens
CELLULAR:
- Reproduce independently
- Can be prokaryotes (no m.b.o’s, single celled) or eukaryotes (m.b.o’s present, multicellular)
NON-CELLULAR:
- Reproduce using host cells
- No metabolic activity
Exotoxins vs Endotoxins
Exotoxins: “secreted toxins”
Endotoxins:” Part of outer membrane released when the bacteria dies”
Bacteria
CELLUAR PATHOGEN
- Unicellular prokaryotes
- Infect any body part
- Cause disease through toxin & enzyme prod (which either effects cell function or cause death)
–> Asexual reproduction (binary fission)
–> Nelsseria meingitidis = meningitis
Fungi
CELLULAR PATHOGEN
- Eukaryotic
- Contains yeast, mold & hyphae (long, branching filaments)
–> Asexual & sexual reproduction (spore formation)
–>Thrush, Ringworm
Worms
CELLULAR PATHOGEN
- Multicellular invertebrate parasite
- Egg, larval and adult stages
- Vary in length
–> Sexual reproduction (life cycle)
–> Parasite (tapeworm) = malnutrition
Protozoa
CELLULAR PATHOGEN
- Single celled eukaryotes
- Can be free-living or parasitic
Mechanisms of action:
1. Cellular respiration inhibition
2. Protein synthesis inhibition
–> Asexual & Sexual reproduction
–> Plasmodium = Malaria
Virus
NON-CELLULAR PATHOGEN
- “Infectious agent composed of genetic material inside a protein coat (capsid)”
- Capsid can be surrounded by liquid envelope
Cause disease through:
1. Viral replication
2.Formation of cancer by affecting gene expression
3. Overstimulation of immune system = organ damage
–> Can independently reproduce = instead inserts genetic material into host cell to replicate.
–> Influenza= flu, Rhinovirus = cold
Prions
NON-CELLULAR PATHOGEN
- Abnormally folded protein in mammals
- Only affects brain and other neural structures
- Only infectious agent that doesn’t contain nucleic acids
–> Induce misfolding to nearing proteins
–> mad cow disease
Allergen
“An antigen that elicits an allergic response”
Allergy
“An abnormal immune response to a substance that is harmless for most people”
Allergic response
“Rapid immune response to normally harmless antigens such as dust/pollen, involves prod. of IgE antibodies by B lymphocytes & release histamines by mast cells”
Immunity def
“Resistance to disease”
Types of immunity
INNATE
- present since birth
- fast acting
- not long lasting
- produces generic responses against classes of pathogens
ADAPTIVE
- Slower acting
- Long lasting
- Specific response
Examples of 2 different types of immunity
INNATE:
- Physical, chemical and biological barriers
- Cell-mediated innate immunity
- Humoral innate immunity (complement & interforns))
- Inflammation and fever
ADAPTIVE
- Humoral or antibody-mediated immunity
- Cell-mediated immunity
Cell mediated response def
“Direct attack by immune cells against pathogens forms the cellular immune responses”
Humoral Response def
“Mediated by soluble molecules in the blood, lymph and interstitial fluid that disable pathogens.”
Immunes Line of defence
1st = “Prevents pathogens from gaining entry into the body”
(Innate - Physical, chemical and microbiological barriers)
2nd = “Rapid, non-specific immune response once pathogens enter body”
(Innate - Cell mediated
- Humoral (complement & interfons)
- Inflammation and fever)
3rd = “Specific defence against specific pathogens”
(Adaptive immune responses)
Physical barriers in animals
“Innate barriers that act to prevent the entry of pathogens into the body”
- Skin
- Mucous secretions
- Hairs in respiratory tract
Chemical barriers in animals
“Innate barriers that use enzymes to kill pathogens and prevent invasion into a host”
- Acidic sweat
- Stomach acid
- Lysosome enzymes in tears & saliva
Microbiological barriers in animals
“Presence of non-pathogenic bacteria in body, which prevent the growth/colonisation of pathogenic microorganisms as they compete for resources/space”
- Bacteria presence in skin, lower gastrointestinal tract, vagina.
Physical barriers in plants
“Innate barriers that act to prevent the entry of pathogens into the body”
- Thick bark
- Waxy cuticles of leaves
- Closed stomata
- Formation of galls
Chemical barriers in plants
“Innate barriers that use enzymes to kill pathogens and prevents invasion into a host”
- Oxalic acid - toxic if ingested
- Phenols - secreted by wounded plants.
What is innate immunity
- First line of defence is breached (physical barrier -> skin isn’t intact)
- second line of defence
- distinguish self from non-self
- phagocytosis (dendritic cells, neutrophils, macrophages)
- inflammation
All cells involved in innate immunity
PHAGOCYTES
(“Innate cells responsible for engulfing and destroying pathogens”)
- Monocytes
- Neutrophils
- - Macrophages
- Dendritic cells
DEGRANULOCYTES
(“have granules in their cytoplasm that contain enzymes that assist in the destruction of pathogens”)
- Natural Killer
- Mast Cells
- Eosinophil
Monocyte Cell - innate immunity
- Phagocyte
- Precursor of macrophages
- Found in blood stream
- Circulating WBC
- Can leave bloodstream and move into tissues.
Neutrophil Cell - innate immunity
- Phagocyte
- Identify and mount phagocytic attack on microbes
- found in bloodstreams
- circulating WBC
- First cells to arrive at infection site
Eosinophil Cell - Innate immunity
- Defence against large parasites (to large to be phagocytosed)
- Attack parasites via toxic chemicals that are released from cytoplasmic granules (granulocyte)
- Found in bloodstream
- Circulating WBC
Natural Killer Cells
+IN BLOOD
+INNATE IMMUNITY
- Elimination of virus-infected & cancer cells by degranulation
Macrophages - Innate immunity
- Develop from monocytes
- Identify, engulf and destroy pathogens, dead cells and debris (phagocytosis)
- Release cytokines to initiate inflammation
- Found in tissues
- Antigen-presenting cells (APC) to initiate adaptive immune response
Dendritic cells - innate immunity
- Engulf pathogens (phagocytosis)
- Present in skin, linings of gut and airways
- found in bloodstream
- Migrate via lymphatic vessels to lymph glands where they act as APC
Mast cell - Innate immunity
- Granules release histamine and cytokines during inflammatory and allergic response
- Located in tissues close to the external environment
- Release cytokines that attract other immune cells to help destroy pathogens.
First & Second exposure of Mast Cells
FIRST EXPOSURE:
1. allergen is inhaled, consumed or contacted
2. Immune cells identify the allergen as non-self
3. B cells produce IgE antibodies
4. IgE antibodies attach to the cell surface of mast cells
5. Mast cells are now primed or sensitised
SECOND EXPOSURE:
1.2nd exposure to the allergen
2. IgE antibodies on sensitised mast cells recognise it as non-self and bind
3. Mast cells activate -> degranulation of histamine -> inflammation
4. Mast cells produce cytokines that recruit more immune cells to sight the allergen and sustain inflammation
Phagocytosis
- Neutrophil
- Macrophage
- Dendritic
STEPS:
1. Pathogen is identified by a pattern recognition receptor (PRR) and engulfed
2. Engulfed pathogen is surrounded by membrane (vesicle) to form phagosome
3. Lysosome fuses with phagosome to form phagolysosome
4. Toxic chemicals from lysosome digest and destroy pathogen
5. Waste is removed from phagocyte via exocytosis
Humoral response of innate immunity
The action of soluble proteins
- Complement protein
- Cytokines (signalling molecule) such as interfons, interleukins.
Complement proteins + role
Involved in the humoral response of innate immunity
“The inactive enzymes dissolved in your blood plasma”
ROLE:
1. OPSONISATION:
Complement proteins stick to outside surface of pathogen = makes it easier for immune system (e.g. phagocytes) to recognise them as foreign
- CHEMOTAXIS:
Complement proteins gather near a pathogen & attract phagocyte = more likely to be destroyed - LYSIS OF PATHOGENS:
Complement proteins join together & form membrane attack complex (MAC) on pathogen surface = pores through membrane
= causes lysis -> via sudden influx of fluid into pathogen = it bursts
Interferons
Humoral - Innate
= PREVENT VIRAL SPREAD
= TYPE OF CYTOKINE = SIGNALLING MOLECULE
- Viral infected cells release a cytokine called interferons
- Interferons bind to receptors on neighbouring cells = enables them to become less susceptible to infections.
- Helps prevent virus spreading between cells.
Inflammation
+ INNATE IMMUNITY
“An acute reaction to an infection (pathogens), injury or damaged tissue that results in cardinal signs (e.g., heat, pain, swelling, redness, pus)”
(Is an early protective response of the innate immune system & is localised around the site of infection)
Vascular stage of Inflammation
+ FIRST STAGE
STEP ONE:
Damaged cells release cytokines = attracts neutrophils
STEP TWO:
Mast cells release histamines = vasodilation
- blood flows to damaged area (redness & heat)
- ^ blood vessel permeability
- ‘leaky blood vessels with protein-rich fluid (exudate) = swelling = pressure -> stimulates pain receptors
Cytokines
Signalling molecule
e.g. interferons - preventing viral spread
Name all the stages of inflammation
- Vascular
- Cellular
- Resolution
Cellular stage of inflammation
+SECOND STAGE
STEP ONE:
Neutrophils squeeze through blood vessel cells
STEP TWO:
- Neutrophils migrate to infection site as first responders, attracted by cytokines released by damaged cells
- Macrophages arrive & release more cytokines to attract more phagocytic cells to the site.
STEP THREE:
- Neutrophils & macrophages phagocytose bacterial pathogens & remove cell debris
- Pus forms from dead phagocytic cells and other debris.
Resolution stage of inflammation
+ THIRD STAGE
STEP ONE:
Once pathogen eliminated - reversal of inflammation occurs:
- Vasodilation stops
- Pro-inflammatory cytokines stop
- Release anti-inflammatory cytokines
Lymphatic system function
+ ADAPTIVE IMMUNITY (3RD LINE OF DEFENCE)
1. Transports antigen presenting ells to secondary lymphoid tissue to initiate adaptive immune response. (main one)
2. Production & maturation of immune cells in primary lymphoid tissues
3. Absorption & transportation of fatty acids to digestive system
4. Removal of excess fluids from body tissues
Structure/parts of lymphatic system
LYMPH
LYMPHATIC VESSELS
PRIMARY LYMPHOID ORGANS
SECONDARY LYMPHOID ORGANS
Lymph
“A fluid that comes from blood vessels and interstitial fluid”
Lymphatic vessels
“Have vessels that force a uni-directional flow”
Primary lymphoid organs (x3 points)
BONE MARROW
- (All blood cells originate here)
- B&T cells produced here
- B-cells mature here
THYMUS
- T-cells mature here
SELF TOLERANCE
- If T&B cells target any self-cells, they are eliminated
Lymph nodes
LOCATION: Along lymphatic vessels (more efficient next to blood vessels)
= where innate system meets adaptive system (T&B cells activated as part of clonal selection & expansion)
- Small bean-shaped structures
- Armpits, groin, neck & abdomen
Structure of lymph nodes
OUTER CORTEX FOLLICLES :
- B Cells
- APC’s (dendritic cells)
INNER CORTEX :
- T Cells
- APC’s (dendritic cells)
MEDULLA CONTAIN :
- Some macrophages
- some B Cells
- Plasma Cells
Initiating the adaptive immune response
The immune system is vital as well as antigen presenting cells (dendritic cells and macrophages)
The adaptive immune system
“Specific response against a specific pathogen & memory retained for future infection”.
- Only required if infection isnt cleared from innate response
- Specificity
- Immunological memory
Components of adaptive immune response
HUMORAL:
- Involves actions of antibodies that identify and bind to extracellular pathogens
B-CELLS: Deliver humoral defences by secreting antibodies that bind to surface antigens on pathogens & label them for elimination.
CELL-MEDIATED
- Eliminates intracellular pathogens and removes infected cell instead of attacking the pathogen.
T-CELLS: Deliver cell-mediated immune responses.
B-cells (lymphocytes) features and function
FEATURES:
- Mature in bone marrow
- Has receptors that recognise 1 specific antigen
- Activated by direct exposure to raw antigens
- Develop to produce antibodies and become a plasma cells
FUNCTION:
(naive B lymphocytes mature into…)
PLASMA CELL (ACTIVATED B CELL):
- Produce antibodies against extracellular antigens
MEMORY B CELLS
- Retain memory of antigens met previously
T-cells (lymphocytes) features and functions
FEATURES
- Mature in thymus & migrate to lymph nodes
- Has receptors that recognise 1 specific antigen
-when APC’s present antigens
- Become different t-cell types
FUNCTION
(naive T lymphocytes mature into…)
CYTOTOXIC T-CELLS (ACTIVATED):
Eliminate infected and abnormal cells
HELPER T-CELLS (ACTIVATED):
Send signals that stimulate B-cells and Cytotoxic cells
MEMORY T-CELLS:
Retain memory of antigens met previously
