Unit #3: Transportation and Respiration

“Blood and Immunity”

What is a Pathogen?

How does our body protect itself from Pathogens?

Pathogen

Immunity

• An infectious biological agent that can cause illness or disease

• The body’s ability to defend itself from pathogens

• Consists of 2 parts:

1. Innate Immunity

• Non – Specific Immune Response that consists of physical barriers, the Complement Cascade and the Inflammatory Response

2. Adaptive Immunity

• Specific Immune Response that identifies, targets and eliminates a specific pathogen

“Innate Immunity”Non-Specific

Defense Mechanisms

Skin and Mucous

Membranes(the 1st line of

defence)

• Skin is a physical barrier that when intact cannot normally be penetrated by bacteria and viruses

• secretions from oil and sweat glands give the skin a pH ranging from 3 to 5 which is acidic enough to prevent the growth of most microorganisms

• BUT, skin can be damaged (cuts and scrapes) which can allow foreign material into body tissues

• Mucous Membranes are physical barriers that line and protect organ systems in the body

• These membranes secrete Mucous and other fluids (saliva, tears, lysozymes) that trap, wash away and/or destroy potential invaders.

The Complement

Cascade(The Early Warning

System

Or

Yellow Alert)

• Should a pathogen breach a physical barrier a series of blood plasma proteins (immunoglobulins) activate

• The proteins will search for and bind to the surface of any pathogen or infected cell making them detectable by White Blood Cells

The Inflammatory

Response(The 2nd Line of

Defence)

• Should the physical protective barriers of the body be breached by foreign material the body, this slightly more vicious line of defence is called to action and triggers an Inflammatory Response

• The cells involved in this line of defence are primarily White Blood Cells and use Phagocytosis to eliminate foreign material (they basically “eat” it)

• There are 6 types of cells involved in the Inflammatory Response

1. Mast Cells(The Thin Blue Line)

• “local law enforcement”

• These cells are found in skin tissue, joints,

connective tissue, muscle and blood vessels

• Mast Cells are NOT blood cells. They

don’t circulate in the blood stream

• These cells will trigger an inflammatory

response when a physical protective barrier

has been breached, damaged, infected or

encounters a toxin

• These cells also coordinate the bodies

allergic responses and wound healing

2. Basophils • the early warning cells

• these White Blood Cells patrol the blood

• during an “injury” blood vessels dilate (widen) carrying more blood to the injured area

• Basophils detect foreign material and release Histamine and other chemical signalswhich begins the inflammatory response

3. Neutrophils • The “Soldiers”

• 60 – 70% of all white blood cells

• attracted to chemical signals produced by the Basophils

• enter infected tissue and “self destruct” destroying foreign invaders

• average life span is a few days

4. Monocytes • 5% of all white blood cells

• the “heavy artillery”

• when these cells detect foreign material they develop and enlarge into Macrophages (“big eaters”)

• as Macrophages, they attach to and ingest (“eat”) foreign material and destroy them with digestive enzymes

5. Eosinophils • the “big game” hunters

• these white blood cells attack larger parasites and worms using an arsenal of destructive enzymes

6. Natural Killer Cells

• the “executioners”

• these cells destroy infected cells, cells harbouring viruses and abnormal cells that could develop into tumours

“Adaptive Immunity”

Specific Defence Mechanisms

(The Last Line of Defence)

• There are a number of parasites, viruses and diseases that the body cannot deal with using non specific methods

• Adaptive Immunity defends the body against specific invaders

• Adaptive Immunity uses 2 Specific Defence Mechanisms:

1. Cell Mediated Immunity (CMI)

• Bone Marrow (Labelled A1) produces Immature T – Lymphocytes (Labelled B) which mature in the Thymus (labelled C)

• They emerge from the Thymus as Mature T –Lymphocytes (labelled D1) or Helper T –Lymphocytes (labelled D2) and are stored in the lymph nodes

• Each T-Lymphocyte has a receptor (labelled D3)

• T- Lymphocytes are stimulated by Antigens(labelled E) from foreign chemical substances (such as viruses, bacteria, cancer cells, fungi etc.)

• When a foreign substance enters the body, the antigen is eventually detected by a T-Lymphocyte with a specific receptor that matches the antigen

• when this happens the T- Lymphocyte is activated (with the help of a Helper T –Lymphocyte) into a Cytotoxic T –Lymphocyte (Labelled F)

• The Cytotoxic T – Lymphocytes then circulate through the blood seeking and destroying cells that contain the antigen

2. Antibody Mediated Immunity (AMI)

• Bone marrow produces Mature B –Lymphocytes (labelled H) which are stored and replicate in the Lymph Nodes

• Like T – Lymphocytes, B- Lymphocytes have receptors (Labelled H1, H2, and H3) that bind to specific Antigens

• Antigens (Bacteria, Fungi, Viruses) stimulate that production of B –Lymphocytes

• Eventually the antigen is detected by a B –Lymphocyte with a specific receptor that matches the antigen

• when this happens the B – Lymphocyte activates and turns into a Plasma Cell(labelled J)

• the Plasma Cell releases a large number of Antibodies (labelled K) which attach to the antigens

• the antibodies attract phagocytes which engulf and destroy the foreign material

• the antibodies stay in circulation for years which results in long-term immunity