1. Innate Immunity & Antigen Recognition Flashcards
What is immunity?
The state or quality of being resistant to infection by innate or adaptive immunity
What are the 4 types of innate immunity barriers?
- Anatomical barriers
- Physiological barriers
- Phagocytic barriers
- Inflammatory barriers
They provide rapid protection that keeps microbial invaders at bay until adaptive immunity develops
What are anatomical barriers?
- Skin
- Mucous membranes
What are physiological barriers?
- Temperature
- Low pH
- Chemical mediators
What are phagocytic barriers?
- Polymorphonuclear leucocytes
- Blood monocytes
- Tissue macrophages
What are inflammatory barriers?
- Influx of phagocytic cells to the affected area
- Cytokine messengers
What are the innate surface protecting mechanisms of the body?
- Eyes: blinking tears
- Mouth: vomiting & saliva
- Nose: Turbulence and sneezing
- Trachea: Coughing, mucus & cilia
- Stomach: acidic & vomiting
- Intestines: normal flora, lysozymes, defensins, proteases and diarrhoea
- Skin: desiccation and desquamation of normal flora, fatty acids
How is inflammation mediated?
- Selectins on the inside of blood vessel endothelial cells tether the passing neutrophils and stimulate them to roll
- When they stop rolling, integrins bind them to the endothelial cells & signal them to emigrate into the tissues to the affected site
What are the 4 essential features of innate immunity that distinguish it from acquired immunity?
- Preformed
- Standardised
- Without memory
- Non-specific
What is the key aspect of the immune system?
The ability of the body to be able to differentiate between “self” and “non-self”
What are the mechanisms that restrict autoimmunity (against self)?
- Useless T and B cells that recognise self antigens are removed in development
- Lymphocytes that react with self-antigens can be suppressed by other cells
- Lymphocytes become unresponsive to activating stimuli
What is non response to self antigens called?
Self tolerance
What are PAMPs?
Pathogen associated molecular patterns
- conserved molecular patterns that act as signatures to alert the innate immune system of the presence of infection
They are recognised by pattern-recognition receptors (PRRs)
e.g. TLRs
What is an antigen?
- Molecule that can generate an immune response in an animal
- Molecule that reacts with preformed antibodies of primed T cells irrespective of it’s ability to generate them
What is an immunogen?
Substances that stimulate a strong immune response when introduced to an animal
What is antigenicity?
The ability of a molecule to be recognised by a product of immune response
What is immunogenicity?
The property of a substance making it capable of inducing a detectable immune response
What is an adjuvant?
A substance, that when administered with an antigen, enhances the immune response to that antigen
What are the 4 general ways that adjuvants promote immune response?
- By prolonging the retention of the antigen
- By promoting accumulation of immunoreactive cells at the site of injection and in draining of the lymph node
- By modifying the activities of cells that are concerned with generating, promoting and maintaining the immune response
- By modification of the presentation of the antigen to the immune system
What is an epitope?
A site on an antigen that stimulates an immune response.
What is an immunodominant epitope?
When the immune system is predominantly raised to a particular epitope
What is a conformational epitope?
Where it is the shape of the molecule that is recognised by the antibodies and not the AA sequence itself
What is a sequential epitope?
Epitopes whose specificity is determined by the sequence of AAs within the epitope
What is a hapten?
A small molecule that can’t initiate an immune response unless it is first bound to an immunogenic carrier molecule
- Once a response is initiated a hapten can react specifically with its antibody
