Immunity

Immunity

First Line of Defence

Aims to prevent pathogens from enerting the body through a physical barrier

Non specific

Stops pathogens getting into your body

Examples

- keratin helps form a physical barrier against the entry of pathogens

- mucus helps trap pathogens

- fatty acids and secretion from tears, sweat and oil glands are toxic to bacteria

- natural fauna of bacteria can outcompete most pathogens

- natural antibiotics with antimicrobial, antiviral and antitoxic properties

Second Line of Defence

Stops the pathogen from spreading and establishing itself in your body

Non-specific

Activation of leukocytes when the pathogen breaks through the first line

Two types of white blood cells:

Phagocytes - white blood that engulf pathogens

Lymphocytes - white blood cells that are not phagocytes, T cells help activate B cells and kill infected cells, B cells produce antibodies

Includes phagocytosis, fever and inflammation

Include mast cells, basophils, monocytes, dendritic cells , natural killer cells

Third Line of Defence

Targets specific pathogens to inactivate, remove or kill the infection

Specific - produces memory cells

Adaptive immune system identifies its weakness and targets them in order to remove or kill them

Determines its response based on the identity of invading pathogen

Does not kick in instantly

Understand how pathogens (bacterial and viral) can cause both physical and chemical changes in host cells that stimulate the host immune responses (introduction of foreign chemicals via the surface of the pathogen, production of toxins, recognition of self and non-self)

Antigens

Self

Produced in the body

Cells, proteins and other chemicals which make up your body

Recognizes them as part of the organism and tolerates them

Non-self

Originate from outside the body

Pathogens and their toxins, chemicals in venom, proteins in food, transplanted organs and blood

Recognizes them as not part of the organism and attacks them

A molecule which is capable of triggering an immune response

Protein based responses

Interferons

- proteins made by virus-infected cells

- secreted and transported to neighboring cells to prevent viral infection from the infected cell

- interferes with viral replication

- enhances phagocyte activity

- slows cell division

Cytokines

Complement proteins

- create pores in invading bacteria causing water to rush in

- coat a bacterium

- opsonization is: complement protein bind to the surface of pathogen acting as a tag to facilitate detection by phagocytes

Natural killer cells

- detect infected cells

- roam the body in 'search' for invaded cells

- puncture the plasma membrane and cause it to lyse (burst)

Immunity in Plants

Recognise that all plants and animals have innate immune responses (general/non-specific) and that vertebrates also have adaptive (specific) immune responses

Physical barriers

Thick outer bark

Waxy water resistant cuticles

Cell wall

Respond to microbial attack by recruiting calluses between cell wall and cell membrane

Shed infected parts

Wounds plugged by resin

Leaf structure - thick waxy cuticle

Waxy cuticle and vertically hanging leaves - prevent moisture film

Hairs and thorns - deter vectors

Stomatal openings weak spots - hair or sunken stomata