Immune system 1

What is the immune system?

Integrated system of cells and molecules that defends against disease by reacting against infectious pathogens

What is a pathogen?

foreign element to the body

What are the main medical relevancies of studying the immune system?

• vaccination

• immunodeficiency treatment

• allergy

• autoimmune disease study

• graft rejection

What’s the concept of vaccination?

fool immune system to think it’s already come into contact with a pathogen = immune memory

What is an autoimmune disease?

immune system mistakenly acting against our own body

What do immunological techniques used in today?

• research

• diagnostics

• therapeutics against cancer eg with antibodies

What is the main characteristic of the innate immune system?

rapid response within hours

What is the main characteristic of the adaptive immune system?

immune memory

What is the specificity of the innate vs adaptive immune system?

broad vs highly specific

Which type of immune system is improved by repeat infection?

adaptive bc has memory

What is the response time of the adaptive immune system?

slow - days

What are different types of leucocytes that act in the innate immune system?

phagocytes, natural killer cells (NK)

What are different types of leucocytes that act in the adaptive immune system?

lymphocytes B and T

What soluble factors are involved in the innate immune system?

lysozyme, complement interferons

What soluble factors are involved in the adaptive immune system?

antibodies

Which type of immune system is most important in babies?

innate immune system - no memory

What types of soluble factors protect against viruses?

interferons

What are antibodies produced by?

b lymphocytes/cells

What are white blood cells/leukocytes derived from?

pluripotent stem cells in bone marrow

What are the 2 main leukocyte lineages?

myeloid cell and lymphoid cell lineages

Name examples of lymphoid stem cells

lymphocytes including plasma cells and natural killer cells

Name examples of myeloid cells

myeloblasts, mast cells, monoblasts

What are plasma cells derived from?

b lymphocytes

What are different types of monoblasts?

monocytes that give rise to dendritic cells or macrophages

What are myeloblasts derived from? What can they give rise to?

myeloid stem cells

neutrophils, basophils, eosinophils

What effect does the innate immune system have on the adaptive immune system?

helps initiate and mediate it

What are different types of barriers to infection?

• keratinised skin

• secretions - sebum, fatty acids, lactic acid, lysozymes

• mucous and cilia

• low ph around 2.5 deters bacteria growth

• commensals

Why can burns or bites lead to infection?

barrier is compromised and they are left vulnerable to infection

Through which pathway do most infections happen?

mucous through gi tract, nose

What are 2 main types of phagocytes acting within the innate immune system?

• neutrophils

• mononuclear phagocytes

Describe neutrophil abundance, life expectancy (lol), and internal organelles (+ their role)

main phagocyte in blood

short lived

fast moving lysosomes releasing enzymes, H2O2 etc

Describe mononuclear phagocytes’ life expectancy, role and types

long lived (months)

help initiate adaptive responses

monocyte (in blood) or macrophage (in tissues)

What type of mononuclear phagocyte is found in tissues?

macrophages

What colour do azurophilic granules give neutrophils? What is their role? How is this evident during colds?

green

release/carry antimicrobial proteins and enzymes that are released to kill pathogens

snot is green = shows active release of the agents to fight off the infection

What is the role of lymphocyte natural killer cells?

• kill virally infected cells non-specifically

• important in self/non-self recognition 

• may kill cancer cells

What do natural killer cells kill?

Kill infected HOST cells, not pathogens directly

How do phagocytes recognise pathogens?

pathogen-recognition receptors (PRRs) that recognise microbe-associated molecular patterns (MAMPs) – distinct from “self”, essential to microbe 

Name an example of phagocyte PRRR and the MAMP it recognises

toll-like receptor 4 (TLR4)

lipopolysaccharide

How do natural killer cells recognise a pathogen?

kill all targets that don’t have MHC self-proteins present on all nucleated cells

How does a natural killer cell kill a target?

doesn’t recognise MHC proteins on their surface, causes the cell to commit suicide/apoptosis

In what cases is MHC down regulated?

in cancer, by reducing MHC-I expression, cancer cells can become "invisible" to T cells, preventing them from being targeted for destruction. 

How does the complement system, part of the innate system, enhance antibody activities (ie adaptive immune system)?

made up of 20 proteins in blood that are activated on infection = bacterial cell lysis

How do defensins act within the innate immune system?

positively charged peptides made by neutrophils disrupt bacterial membranes

How do interferons act within the innate immune system?

Produced by virally infected cells

•  protect uninfected cells

•  activate macrophages and NK cells 

What are 3 mechanisms within the immune system through which soluble factors are produced to allow the riddance of bacterial/virally infected cells?

• complement system (bacteria lysis through proteins)

• defensins (disrupt bacterial membranes through peptides made by neutrophils)

• interferons (infected cells activate macrophages and NK cells to prevent spread)

What are 2 types of soluble factors within the innate immune system that allow cell:cell communication?

cytokines and inflammatory mediators

What are cytokines and their role within the innate immune system?

Small, secreted proteins that bind to cells and regulate the immune response

Name an example of cytokine

interleukins

Name examples of inflammatory mediators

histamine, prostaglandins - small proteins/compounds

What are the 4 characteristics of inflammation?

heat, redness, swelling, pain

In response to what are inflammatory mediators released?

infection or damage

When was inflammation (+ its 4 characteristics) first defined as an integrated response to infection/injury?

roman times

Is inflammation a local or body-wide response to infection/damage?

localised

What causes redness and heat during inflammation in the innate immune response?

dilation of blood vessels = increased blood flow

What causes swelling during inflammation?

increased capillary permeability

During what part of the innate immune response do phagocytes migrate into tissues? How do they do this?

inflammation

early on neutrophils squeeze out of blood vessels

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