Immunology Flashcards
Define immune system
an organized system of organs, cells and molecules that work together to defend the body against disease
Component of the immune system (3)
Organs
cells
molecules
Define immunology
The study of an organism’s immune (defense) system in health and disease
Diseases affected by the immune response (3)
Infectious diseases
Inflammatory disease
Cancer
2 organs of the immune system
Primary and secondary lymphoid organs
Main functions and 2 components of the Primary lymphoid organ
Function: Where lymphocytes (white blood cells) are produced and mature
Thymus and bone marrow
Thymus
school for white blood cells called T cells - develops T cells to not react with itself
Only 10% pass
Rich source of stem cells that develop into cells of the ‘innate’ and ‘adaptive’ immune responses
Bone marrow
Main functions and 2 components of the secondary lymph organ
Function: initiation of immune response
Lymph nodes and spleen
lymph node (3)
- Located along the lymphatic vessels
- Where lymph fluid from blood and tissue is filtered
- Site of initiation of immune response
Spleen (2)
- Site of initiation for immune responses against blood-borne pathogens (as blood is filtered through the spleen, these blood-borne pathogens are removed from the blood and destroyed)
- 20% of immune cells found in gut
Lines of defence
The body ha 3 lines of defence against infection. These act together to maintain the integrity of our internal environment
3 lines of defence
- Physical & chemical barrier
- Arm 1 - Innate arm (cellular defence)
- Arm 2 - Adaptive arm
Already in place Rapid (hours) Fixed Non-specific/limited specifities (detects molecular components shared by many pathogens) No memory
What are the above characteristics of?
Innate community
Characteristics of the adaptive community (5)
Improves during response Slow (days, weeks) Variable Highly - specific (detects molecular components specific to individual pathogens) Has memory
Components of the innate community (4)
Epithelial barriers
phagocytes
Complement
Natural killer cells
Components of the adaptive community (2)
B lymphocytes - produces antibodies
T lymphocytes - makes effector T cells which kill pathogens
Thucydides
First description of immunity (adaptive immunity)
First development of vaccination
Variolation in China - purposeful, controlled injection of something disease causing to protect individuals against small pox
Variolation
Injecting something disease-causing to prevent against a particular disease
Who brought variation to England
Lady Mary Wortley
Benjamin Jesty and Edward Jenner
The first vaccination of small pox
Vaccination
Inoculation (injection) with an innocuous (harmless) biological agent
Elie Metchnikoff
Discovery of phagocytes - Innate immunity
Peter Doherty and Rolf Zinkernagel
Discovery of MHC - self/non self recognition - Adaptive immunity
What part of our body acts as the chemical and physical barrier?
skin, mucous membranes - both act as our body’s first line of defense
Physical defence of skin
2 layers - Epidermis and dermis
Epidermis and its way of preventing pathogens (4)
Outer most layer of skin that forms the main physical barrier to pathogens
- uppermost, outer layer of the epidermis consists layer of dead cells that are constantly shed/replaced which removes the pathogens along with them
- cells of the epidermis are tightly packed together so pathogens cannot skip through easily
- contains dendritic cells (Langerhans cells) which survey for pathogens and alerts the adaptive immune system
- contains keratin
Dermis
Thick layer of connective tissue, collagen, blood vessels and dendritic cells
Chemical defense of the skin (4)
Antimicrobial peptides
Lysosome
Sebum
Salt
Antimicrobial peptides (4)
- short strings of peptide that act as chemical defense against bacteria
- Produced by epithelial cells lining mucosal surfaces and keratinocytes in the skin
- Has a broad spectrum activity against microbes: active against bacteria, fungi and virus
- often work by forming pore in microbial membranes causing microbes to release its nutrients and essential ions (attacks microbes by interfering with growth and reproduction
Examples of antimicrobial peptides and how they work
skin defensins - mostly work by forming pores in cell walls
Cathelicidins - can work by physically attacking microbe and act as chemoattarctants
Lysosome (3)
- enzyme that breaks down bacterial cell wall
- Sweat glands constantly produce sweat which contains lysosomes to constantly break down bacterial cell walls
Sebum
- Produced by Sebaceous glands present in dermis which associates with hair follicles
- fat - oily secretion
- maintains skin at low pH which prevents microbial colonization
Salt (major constituent of sweat)
- secreted by sweat glands in dermis layer of skin
- creates hypertonic environment which can cause water to flow out of microorganisms and dehydrate them
Why does the salty environment created by sweat not affect our own skin
Because our outermost skin layer is dead
Where are mucous membranes found (4)
Lining all interior body surfaces that come into contact with the outside environment
- eyes
- respiratory tracts
- Gastrointestinal tracts
- Urogenital tracts
2 layers of mucous membranes
Upper epithelial layer and bottom fibrous connective tissue layer
Epithelial layer of mucous membranes (3)
- Thin layer consisting of densely packet live cells
- Constantly renewed/turned over due to local stem cells also found in skin)
- contains mucous-producing goblet cells
Main difference between mucous membrane and skin
The outermost layer of skin is dead whereas the outer most layer of mucous membrane is alive
Location of the mucosiliary escalator
Within the lower respiratory tract
Function and structure of the mucosiliary escalator
Function: to withdraw microbes backup from the respiratory tact
Structure
- consists of columnar epithelial cells with cilia at apical surface of the cell
- cells covered in mucous secreted by goblet cells which traps microorganisms
Explain the function of cilia in the mucosiliary escalator
Cilia continuously beat to move layer of mucus along with the trapped inhaled microorganisms up the lower respiratory tract so we can sneeze and cough them out
What contributes to the pathogen defence in the respiratory tract
The mucociliary escalator
How does the gastrointestinal tract prevent microbial growth (4)
stomach - low pH and contain digestive enzymes
Gall bladder - contains bile which can break down lipids and bacterial cell walls
Intestine - contains digestive enzymes
Mucus
Defence system in eyes
Tears which are produced by lacrimal glands and secreted into the ducts in the eye
How do tears contribute to pathogen defence in the eyes
- contain lysozyme
- flushing action
- drainage (tears collected by a drainage system in the corner of the eyes that feeds into the the nasolacrimal duct and drains into nasal cavity and then into the stomach)
Urogenital tract and its way of defence (4)
Urine flow - washes microbes out
lysozyme
low pH
High osmolarity - high number of solute particles to prevent microbial growth
Where are lysozymes present
In tears, sweat, mucus, saliva, urine
What does infection with a pathogen provoke (3)
Anti-microbial peptide production
Interferon production
Activation of the complement system
‘May act as chemoattractants to inflammatory cells’ refers to what
Anti-microbial peptides
Interferon production is a response to what
Infection with a pathogen
What are interferons
A type of cytokine (chemical messengers) made and released by host cells in response to the presence pathogens allowing communication between immune cells
What are antiviral proteins
Type I interferon - a cytokine produced by many host cell types to combat viruses
Interferon mechanism of action
Prevents infection in neighbouring cells by
- signalling unaffected neighbouring cells to destroy RNA an reduce protein synthesis
- signals neighbouring infected cells to undergo apoptosis (programmed cell death)
- Activates immune cells (enhance anti-microbial functions)
Side effects of interferon production
Associated with colds, flu
- muscle aches
- chills
- headache
- fever
3 major hematopoietic stem cell types from bone marrow (in primary lymphoid organ)
- Erythoid
- Myeloid lineage
- Lymphoid lineage
What cells does the Erythoid produce
Red blood cells
What cells does the myeloid lineage produce (4)
Innate immune cells
- Granulocytes
- monocytes
- Dendritic cells
- Platelets
What cells does the lymphoid lineage produce and where they develop
Adaptive immune cells
- B cells which develop in the bone marrow
- T cells which migrate to thymus and develop there
Granulocytes are what type of cell
Innate immune cells
What and where are granulocytes produced
Produced by the myeloid lineage in the blood marrow
What accounts for 3/4 of leukocytes
Granulocytes
Function of granules
Store pre-formed chemicals that allow exact immune responses
Name the 4 types of granulocytes
Neutrophils
Eosinophils
Basophils
Mast cells
Neutrophils (6)
- highly phagocytic
- most abundant granulocyte in blood (45-75% of leukocytes)
- short half life (1-2 days)
- High turnover
- Eat and kill
- Number increase during bacterial infection and will die at the site of infection
- Some phagocytosis
- Low number in blood (1-6% of leukocytes)
- Release toxic granules to kill and breakdown microbe and parasites
- Mediate allergic reaction
- abnormally high in blood during parasitic infection
Eosinophils
Basophils (5)
- No phagocytosis
- very low number is blood (0.5% leukocytes)
- Release granules that mediate allergic responses
- Some chemicals within the granule are very good at drawing in other cells to site of inflammation, can be done through vasodilation
- Fight worm infection
Mast cells
- line mucosal surfaces (not in blood)
- Release red granules - attracts leukocytes to areas of damaged tissue through chemotaxis (in response to injury, infection, allergy etc.)
Which granulocyte exhibits no phagocytosis
Basophils
‘Eat and kill’ describes which granulocyte
Neutrophils
Which granulocyte is not in blood
Mast cells
Which granulocytes mediate allergic responses
Eosinophils and basophils
What do monocytes develop into when they move into tissues
macrophages
Size comparison of monocytes to other cells
4 or 5 times larger than other cells
Monocytes in blood
low phagocytosis - large nucleus and little cytoplasm
Monocytes in tissues
Macrophages: High phagocytosis - large cytoplasm and internal vesicles for digestion
Macrophages
Become resident/sessile or migratory (move through tissues)
3 important functions of macrophages
- phagocytosis
- release cytokines (chemical messengers) to other cells
- Show information about pathogenic microbes to T cels -> important link between innate and adaptive community
Dendritic cells (3)
- Rare but potent
- found in low numbers in blood and all tissues with the environment
- phagocytotic
Which is the most important cell type in triggering immune response? ie. the most important link between innate and immune response
Dendritic cells
3 ways the immune system cells move around the body
- cells carried in blood and lymph
- cells can leave blood and enter tissue
- Lymph and tissue collect onto lymphatic vessels which drain into lymph nodes
When does inflammation begin
Begins when there are injured/infected tissues which release cytokines that allow vasodilation so they become more permeable so cells can get from blood into tissue
Signs of inflammtion
Heat
swelling
pain
redness
What does inflammation cause mast cells to release (3)
Histamine - vasodilation
Prostaglandins - vascular permeability
Leukotrienes - vascular permeability
Explain the process of diopdesis
It is the process by which cells and fluid leave dilated blood vessels in an inflammatory response to get to the site of infection
Neutrophils flatten against vessel wall and can squeeze through blood vessel walls which now has increased permeability and follows chemical gradient of mast cells to get to the mast cells which then causes mast cells to enter the site of infection
Inflammation (5)
- Increased blood flow due to vasodilation caused by histamine
- Increased vascular permeability caused by prostaglandins and leukotrienes
- Allows migration of inflammatory cells into tissue through diopedesis
- Remove the invader and debris
- Promote repair and regeration
At what temperatures does fever occur
> 37 degrees
What is fever caused by
Resetting of the thermostat
Outline the fever response (3)
Pyrogens (interleukin-1) trigger fever response
Phagocytes produce IL-1 after ingesting bacteria
Decrease in phagocytosis leads to decrease in IL-1 therefore decrease in temperature
