Innate Immunity Flashcards
Explain the fundamental differences in innate and adaptive immunity
There are 4 fundamental differences in innate and adaptive immunity which are specificity (what kind of receptors are identified), receptors genes coding, kinds of receptors and differentiation between self and non self.
Innate immune response identify structures that are shared by an entire class of microbes or damaged tissues. These structures are necessary for pathogen infection or when a cell is damaged. The patterns are PAMPs (pathogen associated molecular patterns) and DAMPs (damage associated molecular patterns). The receptors for these are encoded in germline, which gives rise to limited diversity in these receptors. The distribution of these receptors are non clonal, there are identical receptors on all of the cells involved in innate immune response. For adaptive immunity the structure detail of microbial molecules are recognized. These are encoded by genes produced by somatic recombination of gene segments that gives rise to greater diversity. This results in a clonal response with cells having distinct specificities and different receptors. Both of the immune systems can differentiate between self and non self.
What are the intial barriers for innate immunity
There are physical and chemical barriers. Physcial can be the epithelial layer on our skin whereas chemical barriers can be proteases in our saliva and tears in our eyes
How does the epithelial leyer play a role in innate immunity.
It is a physical barrier and it also kills microbes by secreting antibodies such as defensins. Suprisingly there is also some extent of adaptive immune response associated with the epithelial layer of our skin where intraepithelial lymphocytes called the gamma, delta T cells secrete specific antibodies.
What is the role of neutrophils in innate immune response
These are the fastest white blood cells, they are the main phagocytes, neutrophils first respond to a bacterial or fungal infection. Their production is rapidly increased when there is an infection, production is increased by an increase in the prodcution of G-CSF (Granulocyte Colony Stimulating Factor).
Dead neutrphils form pus.
What is a band neutrophil?
How are they significant
It is an immature neutrophils. Their significance is that when we see alot of band neutrophils in the blood that means the body is experiencing a bacterial (she kept saying bacterial specifically) infection. Neutrophils live only for a few hours, band neutrophils go to the circulatory system where they mature.
Name the disease assocaited with neutrophils. What happens in that disease?
It is called Severe Congenital Neutropenia. This disease is associated with severe and recurrent bacterial and fingal infections and also sepsis. This is due to neutropenia (abnormally small number of neutrophils present in the blood). The disease is caused by a dysfucntion in the neutrophil generation mechanism.
The answer is A and D. It is important to know why. In some conditions patients may experience a lack in the prodcution of G-CSF whereas in other cases the actual stem cells are less or faulty which leads to the development of neutropenia.
Name the 2 causes of neutropenia
Increased destruction of neutropils or low rate of prodcution of neutrophils
How do you clinically differentiate between the 2 causes of neutropenia in a patient
We can look at their bone marrow and determine if the rate of production of neutrophils is fast enough or not
Describe the role of macrophages. What kind of cells do they arise from
They arise from monocytes. They have a variety of different roles:
- Tissue resident macrophages
- In all healthy tissues
- Survive for months
- Make cytokines to regulate other immune cells
- Clear dead cells
- They are also involved in tissue repair
Name some of the common PAMPs
These are basically essential cellular structure components that the microbes have, they are essential for infections and proliferation of the microbes. A few of these examples are:
- Peptidoglycans
- Lipopolysaccharide (LPS), it is an endotoxin
- Terminal mannose residues
- Unmethyated CG rich DNA
What recognizes the PAMPs
PRRs: Pattern Recognition Receptors
The first class of these receptors is the Toll like receptors (TLRs). These can be either on the cell surface membrane to identify bacterial and fungi or they can be in the inside of the cells to identify intracellular parasites such as viruses and plasmodium.
Intracellular TLRs are called Endosomes
Explain the process of TLR singaling
I believe what she described here was a cell surface membrane TLR.
This receptor has a protein associated with called the MyD88 which interacts with IRAKF. Then there is cascade of signaling factors involved which eventually leads to NF kappa B transcription factor triggering gene transcription that induces an inflammatory response.
It is important to know that there are rare inherited conditions that are associated with faulty TLR singaling that predisposes an individual to a higher risk of infections
What receptors are found inside the cells that are assocaited with detecting EXTRAcellular microbes
These are called NOD like receptors
Explain the mechanism of action of NOD like receptors
The one that we need to know about in this lecture is called NLRP-3. It detects extracellular bacteria by sensing for bacterial products, K+ efflux, reactive oxygen species or crystals.
NLRP3 forms the NLRP3 inflammasome which causes activation of caspase 1. Caspase 1 then cleaves IL 1 beta (from pro-IL1 beta). This activates IL1 beta which then leads to the development of acute inflammation in that region.
What are the functions of IL1beta
It induces fever, it induces inflammation at the site of infection and it recruits neutrophils and monocytes to the site of infection
What are some of the other receptors that are employed to idenitfy extracellular microbes (other than TLRs and NLRs)
- Mannose receptors - recognize terminal manose residues
- Dectins - recognzie fungal glycans
- Complement System
What are the 3 pathways to activate Complement system
- Classical pathway - antibodies bind to the microbe
- Alternate pathwya - proteins binds to the microbe
- Lectin pathway - manose binding lectin (MBL) bind to the terminal manose residue on the glycoproteins present on the surface of the microbes
Describe the mechanism of compliment system in detail. What specific substances are involved in this pathway and what are their functions?
This consists of a system of proteolytic enzymes, which upon activation cleaves other protein that leads to an amplification of the signal and a cascade of events. The eventual end product of this cascade is that C3B binds to the microbe that facilitates its opsonization. Some other chemicals worth remembering:
- C3A and C5A causes inflammation
- C5 leads to the development of MAC complex on the microbe that leads to its lysis.
Define the acute phase response
It is part of the compliment system, an important part of the innate immunity where plasma proteins leads to the lysis of microbes that are present in the circulatory system.
There are 3 major plasma proteins involved in this process
- Collectins - which are MBL, binds to the terminal manose residue on the glycorproteins that are present on the cell wall or cell surface membrane of the micrbes. Lung surfactant is also calssified as a collectin.
- C Reactive Proteins (CRPs) - they have 5 heads, binds to the phosphrylcholine which leads to opsonization of the microbes, they are also capable to activate the compliment system
- Lastly some chemicals directly associated with acute phase response are TNF alpha, IL-1 and IL-6 induce this acute phase response such that collectins and CRPs are quickly made in the liver
What is the process of leukocyte extravasation
What does TNF and IL1 do
They induce vasodilation and inflammation
What are the clinical signs of inflammation
- There is heat and redness due to vasodilation
- There is swelling, pain and loss of function due to increased permeability
