Innate and adaptive immunity Flashcards
2 stem cells populate the entire immune system, they divide into 2 linages, what are they?
- Those that give rise to cells which populate the innate immune system i.e. RBC and platelets
- The common lymphoid cells that give rise to the adaptive immune system
Describe the specificity and memory of innate immunity
Non-specific and no memory
Give some mechanical examples of innate immuntiy
- Body surface: skin, fur - prevents pathogens from entering the system via the skin
- Cilia in respiratory tract - traps pathogens and forces them out via exhalation
- Flushing by liquids e.g. tears, urine, diarrhoea
- Mucus as a barrier - over production when there is a pathogen
Give 2 physiological changes of the innate immune system
- pH changes
- Pyrexia = fever/change in body temperatre
Describe the structure and function of defensins
- Small 15-20aa proteins
- Found in many cells and tissues, they lack specificity
- Active against bacteria, fungi and viruses
- Bind to the microbe membrane
- Create a hole and disrupt the homeostasis of the pathogen as they cause a gradient between the internal and external environment
- Cause the dilution of essential molecules within the pathogen
What is the function of lysozyme and sweat gland secretions?
Attack peptidoglycan walls of bacteria
Describe how the myeloperoxidase system works
- Enzyme found mainly in lysosomes, granulocytes and macrophages
- Kills bacteria and other pathogens by production of toxic hypochlorite and a single oxygen
- Causes a fatal compromise in their redox system causing them to stop respiring
Which molecule is used as an indicator for an inflammatory response?
Acute phase proteins
How do macrophages function?
By ingesting (phagocytosis) and killing microorganisms
How do neutrophils function?
- Phagocytosis
- Release of granules into the external environment
How do Mast cells/Basophils/Eosinophils function?
- They have receptors for antibodies and increase vascular permeability
- Basophils and Eosinophils are also granulocytes
What is the name given to bacteria in the gut that cause no harm?
Commensal bacteria
How can commensal bacteria prevent other bacteria infections?
- Inhabit mucosal surfaces, especially in GI & respiratory tracts, and skin.
- Prevent attachment of pathogenic bacteria and hence block their invasion and infection.
- Competitive exclusion
What effect do antibodies have on competitive exclusion?
- There will be a large colony of commensal bacteria
- Antibiotics kill many of these commensal bacteria
- This allows pathogenic bacteria to access tissues that were previously inhabited, causing infection
Adaptive immunity is built from which 2 cells?
T and B cells
What are the 3 defining features of adaptive immunity?
- Very specific
- Self/non-self discrimination (Distinguishing between the hosts own proteins and the proteins of the pathogen)
- Memory
After the first challenge, when will acquired immunity peak?
About 2 weeks after
Describe the rates of response of the innate and active immune systems upon the first challenege
Upon the 1st challenge the active immune system responds at a slower rate compared to the innate immune system
What is generated by the adaptive immune system during the primary response?
Memory B-cells
What are the 3 stages of action when defending against a microbial invasion?
- Physical barriers
- Innate immunity - inflammation, defensins, lysozyme
- Adaptive immunity - antibody production, cell mediated immunity
Provide a definition of an antigen
Is any molecule that can bind specifically to an antibody or antigen receptor.
Their name arises from their ability to generate antibodies
Provide a definition of an epitope
Is a site on an antigen recognised by an antibody or antigen receptor.
They are short peptides derived from a protein antigen.
It can bind to an MHC molecule and is recognised by a particular T-cell
Provide a definition of an antibody
Is a protein that binds to a particular substance - its antigen.
Each antibody has a unique structure that enables it to bind specifically to its antigen.
All antibodies have the same overall structure known as immunoglobulins.
