First Line of Defence

First Line of DefenceBy Eden Aspinall and Theresa Hudson

Expected Learning:• To develop a

comprehensive understanding of the first line of defence in the immune system.

Physical Barriers: Animals Integumentary system (skin) is the main

barrier, preventing pathogens from entering Like a blockade? Mucosal (mucus) membranes inhibits

bacteria Natural agents like sweat are secreted to

eradicate bacteria The body grows bacteria to provide a natural

competitor for other bacteria. http://

www.youtube.com/watch?v=Non4MkYQpYA&feature=related

Skin as a Barrier

Joharn‘s yucky ear!

BLEGH!

Natural Agents as a Barrier

Chemical Barriers: Animals Certain white blood cells destroy invading

microorganisms. Sweat and fatty acids have properties that

repel pathogens The immune system produces substances

and agents that are designed to attack the invading microorganisms.

Enzymes like lysozyme, found in tears and saliva ‘lyse’ or burst pathogenic substances

White Blood Cells asa Barrier

Immune System as a Barrier

What about plants? What!? They have no immune system!?

They actually don’t!!Many plants are resistant to pathogens and have several characteristics that protect them from infection from things such as insects and nematode worms.

Physical Barriers: Plants External covering of plants works like skin

while repelling bacteria. Plants have physical responses to prevent

infection spreading such as ‘galls’ Galls, like scabs, form a sort of ‘cork’ when a

plant is infected These stop the parasite or infection from

spreading throughout the plant. Often, the stomata is a common ‘entry point’. Thorns are another type of defence

Chemical Barriers: Plants Produce chemicals that act as

antibiotics. Some leaves have high silicon content to

prevent harmful pathogens. Some trees produce oils or gum to repel

or reduce infection Resins, Tannins and Phenolic substances

also help repel malevolent substances. ‘The tale of the Ouchie Mouth’

Chemicals as a Barrier

Internal Organs and Tissue in the Immune System Bone marrow – Stem cells differentiate

into a range of different cell types before leaving the bone marrow, mainly T cells and B cells

Thymus – T cells go through thymic selection and circulate in the bloodstream after maturing.

Spleen – B cells travel from the bone marrow into the spleen and mature.

More Organs and Tissues in the Immune System Lymph Vessels and Nodes Other Lymphoid Tissue ^Ears, eyes, gut etc.

Self and Non-Self Materials made by the body’s own cells is

called self. Foreign material is called non-self. When invaded by non-self material, the

immune system is activated. Self can be: blood cells, plasma,

reproductive cells, etc. Non-self can be: Toxins, dirt, bacteria,

pollen etc.

Major Histocompatibility Complex MHC: A cluster of genes that encode

information for the production of marker proteins on the surface of cells.

Two types of ‘markers’ in our bodies:Class 1 markers: Found on every cell except red blood cells. Class 2 markers: Found on Macrophages B and T cells.

How do they tell the difference? T and B cells recognise similar markers

on other cells and ignore them, as they are not a threat

They respond to the foreign MHC markers on ‘invaders’.

Like if you saw someone in the enemy’s uniform sneaking around your camp

When they come into contact with foreign, or non-self material, they

Antigens Any foreign substance that causes the

immune system to create antibodies against it

These activate the production of ‘antibodies’

‘Self-antigens’ can also be found in immune cells. These are like ‘markers’

Homework & Reflection Reflection

Answer the multiple choice questions on the following slide.

Homework Quick check pg.

250, questions 1 - 3

Reflection: Multiple Choice Question 13 First-line defences that mammals have

against invasion by disease-causing bacteria include

A. lysozymes. B. interferons. C. antibodies. D. killer T cells.

Reflection cont’d Question 19 First-line defence mechanisms in

humans include A. development of fever. B. action of phagocytes. C. use of antibiotics. D. presence of cilia.

Reflection cont’d Question 8 Evidence that a vascular plant has an

infectious disease includes the A. drying out of root hairs during drought. B. yellowing of leaves due to deficiency of

iron. C. presence of spores on fungal hyphae

growing out of stomata. D. presence of nitrogen fixing bacteria in the

root nodules of legume plants.