Intro to immune system Flashcards
What is the immune system?
- a defensive system evolved over millions of year of constant battle with fast evolving pathogens
What are the characteristics of the immune system?
- diverse and complex
- overlapping/ partially redundant system
Why is there so much evolution involved in the immune system?
- To make sure there isn’t a single point of weakness in the system
What are the components to the animals immune system?
- many tissues
- cells
- molecules
What are the critical aspects of the immune system?
- Barrier
- Identify
- Kill
- Remember
The immune system can be divided into what two arms?
- Innate immune system
- Adaptive immune system
What is the innate immune system present in?
- present in all plants, invertebrates and vertebrates
What type of recognition does the innate immune system have?
- non-specific recognition with no specific memory response
What is the adaptive immune system present in?
- vertebrates only
- and is not the same in every vertebrate
What recognition does the adaptive immune system have?
- specific recognition with an ability for specific memory responses
How are receptors in the innate and adaptive immune cells different?
- Fundamentally different in the way they are generated
What does different generation of receptors in immune cells lead to?
- leads to differences in specificity
Describe innate recognition:
- broad groups of pathogens
- e.g., gram positive and negative but not the specific bacteria
Describe adaptive recognition:
- can work at strain level and be very specific in identification
How does the innate immune system know when and what to attack?
- Has to recognise either a breach in barrier or what pathogen has breached the barrier
How does the innate immune system identify pathogens?
- through self/non-self molecules
- recognise things that are not part of animals body e.g., uniquely different
What type receptor does the innate immune system have?
- pattern recognition receptors (PRRs)
What are PRRs?
- innate cell receptors that recognise conserved non-self molecules
Name an example of a non-self molecule:
- Lipopolysaccharide (only in gram negative bacteria)
What are non-self molecules collectively known as?
- Pathogen-associated molecular patterns (PAMPs)
What does PAMPs being highly conserved mean for recognition?
- hard for pathogens to evade recognition
What happens during the innate immune recognition response?
- The PRR bind to the PAMPs
What are the 7 major cell types involved in the innate immune cells?
- dendritic cells
- macrophages
- neutrophils
- eosinophils
- basophils
- mast cells
- mast cells
What do all innate immune cells possess?
- PRRs
What means animals are more likely to suffer bacterial infections?
- issues with the toll-like receptor 4
What can trigger the innate immune recognition?
- By damaged associated molecules
What are examples of immune cell receptors?
- TLRs
- RAGE
What are the molecules not released in mammals?
What happens when they are found outside of the cell?
- DNA not found outside nucleus
- HMGB1 - DNA binding proteins
- these damage associated molecules are recognised
What is the innate immune response based on?
- based on receptors that do not change (germline inherited)
What can the innate immune response recognise?
- recognise conserved structures (e.g., LPS)
- non-specific, broad groups of pathogens
- also can recognise conserved damage-related molecules
What cells are used in the adaptive immune response?
- B lymphocytes
- T lymphocytes
What do B lymphocytes do in the adaptive immune response?
- secrete antibodies (immunoglobulins)
What are the two major T lymphocyte cell types?
- A/CD4+ T lymphocytes
- B CD8+ T lymphocytes
What do A/CD4 + T lymphocytes do?
- Helper T lymphocytes which help other cells
What do CD8+ T lymphocytes do?
- cytotoxic T lymphocytes (kills cells - important in infected host cells) and intracellular infections
What are B lymphocytes?
- B-cell receptor (BCR) - a surface transmembrane immunoglobulin (antibody on surface)
What are T lymphocytes?
- T-cell receptor (TCR) - a surface transmembrane immunoglobulin
What are both B lymphocytes and T lymphocytes referred to?
- antigen receptors
What is an antigen?
- any substance that can bind to specific lymphocyte receptors and so induce an immune response
What substances can be classed as antigens?
- lipids
- carbs
- proteins
- a pathogen will contain multiple antigens, don’t need to be conserved
What are epitopes?
- most antigens have multiple specific regions that the antibody or T cell receptor binds to this is called an epitope
Unlike innate receptors what can adaptive TCRs and BCR do?
- they can differ between cells in the same body
What means the adaptive immune system can respond to anything?
- the TCRs and BCR can differ between cells in the same body
- created by random recombination of segments of receptor encoding genes early in cells
Describe antibody formation?
- initially each pre-B cell has the same light chain and heavy chain genes (these encode antibody)
- these genes have multiple options
- this creates vast diversity so can bind to anything
How do the innate and adaptive immune responses work?
- innate and adaptive immune responses evolved together in vertebrates = lots of links
Most responses to viruses, bacteria, fungi, helminths, ectoparasites are what?
- are both innate and adaptive
The immune system encompasses numerous cell and tissues
what cells does it include?
- includes immune cells and non-immune cells
What tissues does the immune system involve?
- includes tissues evolved for immunological function = lymphoid tissues and other tissues
What are white blood cells called?
What percentage of the whole blood do they make up?
What is there main function?
- known as leukocytes
- < 1% of whole blood
- main function is killing invading pathogens
Describe red blood cells:
- 1 cell lineage = myeloid
- one major function
- few differences (related to age of cells)
Describe white blood cells:
- 2 cell lineages = myeloid/lymphoid
- many functions
- many differences (morphology, size, cell types)
What is myelopoiesis?
- process of myelocyte production
What is lymphopoiesis?
- process of lymphocytes production
How are NK cells, T and B lymphocytes made?
- hemocytoblast stem cell in bone marrow form …
- lymphoid stem cells which go on to form …
- NK cells, T and B lymphocytes
Describe how neutrophils, eosinophils, basophils and monocytes are formed?
- hemocytoblast stem cells in bone marrow form …
- myeloid stem cells which form …
- myeloblast which forms …
- neutrophils etc…
What are the different types of WBCs?
- neutrophils
- monocytes
- eosinophils
- basophil
- lymphocytes (bunched together in count)
What are neutrophils?
- earliest responders to any infection = front line
- largest percentage of WBCs in most species
What is the percentage of neutrophils in:
1. dogs
2. horses
3. cows
1 . 58-85%
2. 52-70%
3. 15-30%
- sidenote - in cows/sheep lymphocytes are higher
What is the lifespan of neutrophils and describe what they look like under a microscope?
- short life span (1-4 days)
- granulated (faint granules in cytoplasm)
- multilobed nucleus
What is the main role of neutrophils in immune response?
- phagocytosis (eating pathogens)
- anti-microbials (via degranulation)
What are monocytes?
what percentage of WBCs do they make up in dogs, horses and sheep?
- in the bloodstream they are called monocytes
- dogs = 2-10%
- horses and sheep = 0-6%
When monocytes arrive at tissue what do they develop into?
- macrophages
- dendritic cells
Monocytes tend to function when they get into tissues - what do they look like and what is there lifespan?
- long lived but only in bloodstream for 1-3 days
- large cells (largest leukocytes)
- agranulated (no dark granules)
- kidney-beaned shaped nuclei
What is the main role in monocytes in the immune response?
- phagocytosis
- antigen presentation very important in adaptive
- cytokine release
What are cytokines?
- small, soluble proteins (peptides and glycoproteins)
- intracellular messengers of the immune system
Name two cytokines:
- interleukins (IL-2)
- interferons (IFNy)
What do cytokines do?
- bind to specific membrane receptors leading to signal
- can have short or long pathways
What are chemokines?
- subset of cytokines
- specialised function = chemoattractants
Give two examples of chemokines?
- CXCL8
- CCL2
What do chemokines do?
- mobilise immune cells to move to tissues or within tissues to right place
- they produce a gradient for the cell to follow in order to reach the correct site
What do eosinophils look like under a microscope?
- bilobed nucleus
- more heavily granulated
What are the percentages in eosinophils in dogs, horses and cattle?
- dogs = 0-9%
- horses = 0-7%
- cattle = 0-20%
- may not see them in every BC
How long do eosinophils spend in the bloodstream and in tissues?
- approx. 30 min in bloodstream
- 12 days in tissue
What can a rise in eosinophils suggest?
- rise can suggest helminth/allergy response
What are the main roles of eosinophils in the immune response?
- release inflammatory mediators (via degranulation)
- release a-helminth molecules (via degranulation)
- do not release histamine
What are basophils involved in?
- involved in helminth/allergy responses
What are the percentages of basophils in dogs, cats, horses and cattle?
- dogs and cats = 0-1%
- horses and cattle = 0-2%
Where are basophils normally located?
- normally not found outside of the bloodstream
- more specialised for blood
What is the lifespan of basophils and what do they look like under the microscope?
- short-lived (3 days)
- granulated
- bilobed nucleus
What are basophil main role in the immune response?
- less well defined
- igE triggered degranulation
- release histamine and other mediators
Lymphocytes are a lot more common what cells do they include?
- B lymphocytes
- T lymphocytes
- NK cells
Lymphocytes are hard to distinguish describe why and what you can work out by looking at them?
- cant really distinguish in a basic blood smear
- can tell mature vs immature based on cytoplasm
What do lymphocytes look like under the microscope?
- agranulocytes (like monocytes) - so clearer cytoplasm
- small - little bigger than RBCs
- nuclei (relatively circular) - not bilobed, take up more of cell
