Immunity Heroes:   Skin, hair, mucus, saliva   White Blood Cells:

  B-Cells   T-Cells   Macrophages

 Germy Villians:   Pathogens:

  Bacteria   Viruses   Microorganisms

 Any foreign particle that enters the body is called a PATHOGEN

 Usually a bacteria or virus.  Comes in many different

forms and attacks the body

 ANTIGEN - the part of a pathogen that produces an immune response

NONSPECIFIC IMMUNITY is a defense system that responds immediately to protect the body from all foreign substances, WHATEVER they are…

 Nonspecific - the same response works against many different infections  Methods:

 The Skin (main defense)  Mucus membranes  The inflammatory response  Phagocytosis

 The first line of defense is the organ system called the INTEGUMENTARY SYSTEM

 This Consists of:  The Skin - epidermis  Hair – keratin protein  Nails – dead skin cells filled with keratin

 Often referred to as the most important of our defense systems  This is the largest of all body systems

 Methods of protection:  Acts as a barrier  The acid pH of skin inhibit bacteria from growing

From the latin word “integere” which means to

cover

 You: “Your epidermis is showing!”

 Response: “What! It is?” (meanwhile they are looking around for this so called epidermis…usually at their butt or something)

 You think: “Wow this person is dumb, but you decide to play along until they realize it”

 Pronounced (Fay-go-sites)

 Once invaders make it past the mechanical barriers of our body, phagocytes are the cells that engulf or ingest them

 Ex: neutrophils, macrophages

 Called phagocytosis:   Arm-like extensions pull the

pathogen into a storage organelle

  Lysosomes secrete enzymes for breakdown

  Broken material is then released

 Called Natural Killer Cells (NK Cells) as they kill infected body cells

 Yep, these cells can kill cancer cells and virus-infected cells before the immune system does

 They are less “picky”  They attack by releasing lytic

(cutting) perforin chemicals that slice a target cell’s membrane and nucleus

 This is a response to ANY body tissue injury (nonspecific)

 Begins with a chemical alarm that releases histamine and kinins:   Causing dilation of blood vessels   Causing leakage of capillaries   Triggering pain receptors   Attracting phagocytes (called

chemotaxis)

  Increased blood leads to redness  Capillary breakage leads to swelling  About an hour after, neutrophils

begin to engulf dead cells and pathogens

“Pus” is just a mixture of dead

neutrophils, broken cells, and dead

pathogens

The Immune System is the Third Line of Defense Against Infection

The Immune Response

  Immunity – immune comes from the latin word “immun” and means FREE   This is our built-in SPECIFIC DEFENSE SYSTEM

  Immune Response - third line of defense   Involves production of antibodies from immune cells

  These cells are called LYMPHOCYTES

  Remember… an antigen is a molecule from a pathogen or foreign organism that provokes a specific immune response.

Duality of Immune System

  Humoral (Antibody) Immunity   Involves production of antibodies

against antigens

  Antibodies are produced by certain lymphocytes called B cells   B cells that are stimulated will

actively make antibodies

  Antibodies are found blood plasma, lymph, mucus and the surface of B cells

Duality of Immune System

  Cell Mediated Immunity   Involves the production of

lymphocytes called T cells that recognize foreign antigens on the surface of cells   Helper T cells

  Cytotoxic “Killer” T cells

  T cells activate the activity of other cells: B cells, macrophages, neutrophils   They are WBC stimulators

Lymphocyte Activation

The big eater   Makros = large   Phagein = eater   Macrophages are large white

blood cells that eat any pathogen that is foreign or marked with an antibody

  They are considered to be phagocytes as they clean up cellular debris by engulfing it

  They are attracted to the site of infection by chemicals “smells” given off by dying cells  Histamine and kinins

Are they really white?

  WHITE BLOOD CELLS or LEUKOCYTES are actually the defenders of the body

  Cops in the blood stream…   They consist of:

  Lymphocytes (B Cells and T Cells)   Granulocytes (Neutrophils)

  Their goal is to maintain homeostasis   White blood cells travel along a different

system of highways in the body called the LYMPHATIC SYSTEM   This system transports lymphocytes (B Cells and

T Cells) in the body   Consists of the lymph nodes, spleen, and lymph

vessels

The PLASMA B-Cell

  B-LYMPHOCYTES are named after their location of creation (the Bone marrow)

  One form of B-Cell is the Plasma Cell

  On the surface of each Plasma Cell are receptors to recognize foreign antigens   These receptors can match only one

antigen

  Once B-Cells find a match – they create ANTIBODIES to mark the bacteria or virus

Antibodies

  This Y-shaped protein is created by Plasma Cells

  It attaches to antigens so the body can identify pathogens…and DESTROY them!

  Their main goal is to mark antigens, and signal for help…

  Bacteria and other pathogens that are covered in antibodies are more likely to be attacked by cell eating MACROPHAGES

Epitopes:  Antigen  Regions  that  Interact  with  Antibodies  

How Antibodies Work?

  Antibodies are unique for a specific antigen or foreign body invader

  They are “Y” shaped in order to land on the target site and recruit cells to destroy the infection   Some act as labels to identify

antigens

  Some cause the clumping together of bacteria, to make them less likely to spread

Consequences  of  Antibody  Binding  

Some B-Cells are smart…

  Activated B-Cells are sometimes called MEMORY B-CELLS.

  Memory B-cells start producing ANTIBODIES as soon as an antigen comes back

  When the pathogen infects again, it is destroyed before any symptoms show

  This is like a police dispatcher receiving the same call, and the police station already knowing what to do…

  This is why we don’t get the same exact cold twice

Antibody  Response  After  Exposure  to  Antigen  

The T-Helper Cell

  Also called CD4+ cells (for a protein on their surface)   These are WBC’s whose primary task is to activate B-Cells and

Cytotoxic T-Cells   T-Helper cells are activated by Dendritic Cells   And they are like the security guards with walkie talkies…   Helps relay chemical messages in order to let the body know that

foreign antigens are present

Cytotoxic “Killer” T-Cells

  Also called CD8+ cells (for a protein on their surface)   These are specialized white blood cells whose primary task is

to attack our “good” cells that have already been infected   T-Helper cells activate Killer T-Cells   Infected cells are recognized by antigens on their surface…

Lymphocyte Function

1. Bacteria With Antigens on Surface

Macrophage

T cell

B cell

4. B Cells make antibodies that bind to bacterial antigens. This helps other cells identify and destroy bacteria

3. Helper T cells activate B cells

5. Macrophages digest bacteria, and display antigens on their surface

Section 40-2 Immunity

2. Bacterial antigens stimulate B cells

Macrophage

T Cell

Helper T Cell Killer T Cell

Infected Cell

Antigens are displayed on surface of macrophage

T cell binds to activated macrophage

T cell, activated by macrophage, becomes a helper T cell

Helper T cell activates killer T cells and B cells

Killer T cells bind to infected cells, disrupting their cell membranes and destroying them

Immune Response