BIOL 273 - Unit 6.3 Flashcards
Basic steps of immune response (regardless of foreign substance)
- Detection and identification of foreign substance
- Communication with other immune cells
- Recruitment of help and co-ordination of the response
- Destruction or suppression of the invader
What kinds of chemical signalling does the immune response use
Antibodies (Ab) - bind to antigen as a signal
Cytokines - affect growth or activity of other cells
What are the two main categories of immunity
innate and adaptive immunity
- overlap and cooperate in mounting responses to pathogens
Describe the response time of innate immunity
Innate - more rapid , less specific response - can lead to adaptive
Describe the response time of adaptive immunity
response is slower, more specific
Describe innate immunity
present before pathogen is encountered and is non-specific
response begins within minutes to hours, and it does not remember past infections
some non-specifc cell types and proteins
inflammation is distinctive in innate immune response
Present in all organisms
Describe adaptive immunity
directed at specific invaders (aka acquired immunity)
Develops after the pathogen is encountered and the response takes days to weeks
Remembers past infections
Only found in vertebrates
What can adaptive immunity be further divided into
Cell-mediated immunity
Antibody mediated immunity (humoral immunity)
Line of defences of innate immunity
physical and chemical barriers provide the first line of defence (most vulnerable since exposed to outside)
Second line of defence are patrolling or stationary leukocytes and blood proteins (react same way to every infection)
(provide clearance of pathogens or containment of the pathogen until adaptive response kicks in)
Innate immune system cells
Majority are phagocytes (destroyes/suppress invader ingesting it)
Attract other cells by secreting cytokines which will attract other immune cells via chemotaxins
- cells that are attracted are cytokines, products of tissue injury, bacterial products
Describe how phagocytes engulf invaders during phagocytosis (innate immunity)
Phagocytes leave the circulation and enter tissue through capillary walls (aka extravasion)
They identify the invader by chemical cues which interacts with receptors on the phagocyte membrane
Many receptors bind sequentially to allow the phagocyte to engulf the invader
Movement of pseudopodia via actin filaments push the cell around invader
What happens in phagocytosis when pathogens do not have surface features that can be recognized directly by phagocyte (innate immunity)
blood proteins bind to and coat the pathogen to “tag” it
Phagocytes have receptors for these blood proteins
“Tagging” a pathogen is called opsonization
A protein that can do it is an opsonin
Phagocytosis: what happens once the pathogen is ingested
the particle is in a vesicle called a phagosome
These fuse with lysosomes which contain digestive enzymes and chemicals that kill the pathogen
- forms a phagolysosome
Pus
Dead phagocytes, tissue fluids and debris collected at the site of injury
Those phagocytes that are also APCs present antigens from digested bacteria on the surface of the APC via class II MHC
Natural killer cells
lymphocytes associated with innate immunity
- kills an infected cell that is not presented with MHC I
- do not have specific receptors as seen in B cells and T cells
- They bring out apoptosis in pathogen-infected cell
- Can also attack tumour cells
What do natural killer cells produce
cytokines such as interferons ; interfere with viral replication
- IFN alpha and beta - induces an “antiviral state” in nearby cells that prevents viral replication
- IFN gamma - activates macrophages and other immune cells
Role of chemical mediators
- play a role in the innate response
- create the inflammatory response - red warm swelling in skin is hallmark of innate response
- caused by cytokines that are released by macrophages
Describe the purpose of inflammatory response of chemical mediators
- serves as a signal to attract other cells and chemical agents to the site
- Increase capillary permeability and causes fever
- A physical barrier is produced - prevent the spread of pathogen
- tissue repair is promoted
Interleukin 1 (IL-1)
produced by cells within innate immune system such as macrophages - mediates effects of inflammatory response of chemical mediators
- act on endothelial cells lining the blood vessels - loosens junctions between cells
- act on liver cells to produce blood proteins involved in damage control
- Induce fever
- Stimulate cytokine production
Complement proteins
- take part in innate response (blood proteins)
- activated by sequential proteolysis
- some are opsonins, some are chemotaxins , some form membrane attack complex and make holes in pathogen membranes
Describe the Membrane Attack complex
Use of complement proteins in innate response:
- results in “MAC Attack”
C1 binds to an anitogen antibody complex on an invading pathogen, causing complement components to split in two
proteins continue to split util C3a attracts phagocytes to infection site
fragments joins to form membrane attack complex, which makes a hole in the pathogen’s plasma membrane, water rushed into the hyperosmotic cytoplasm, causing the pathogen to lyse
What is adaptive immunity started by
products of innate immune response
Adaptive immune system cells
lymphocytes and lymphocyte products
1. Natural killer (which is in innate response)
2. B cells (activated form = plasma cell)
3. T cells (Tc and Th and Tregs)
clone
a population of lymphocytes that has a specificty towards one particular antigen
