1. Immune System

4.  The immune system defends against threats in our environment  Two types of immunity  Innate  which you are born with  Acquired  which you develop throughout your life

5.  When faced with a invader your body has:  1 st line of defence  2 nd line of defence  3 rd line of defence  Just like an army

6.  Barriers such as: cilia, HCL, skin and mucous membranes  The skin  has acidic secretions which kill bacteria  The mucous membranes secrete:  tears, saliva, perspiration  All contain lysozyme an antimicrobial enzyme that destroys the cell walls

7.  It is non-specific  It involves:  neutrophils  macrophages

8.  Macrophages:  engulf invading organisms by phagocytosis  display the foreign antigen on their membrane

9.  Neutrophils:  are attracted to a signal damaged cells give off and migrate towards them  engulf the microbe and macrophage  Release lysosomal enzymes to digest both (microbe and macrophage)

12.  What remains?  Fragments of proteins, dead WBCs, dead microbe = PUS

13.  The damaged tissue initiates a inflammatory response….. redness, swelling and pain (this is to keep you from using the damaged tissue)  Now things are more serious…… the third line of defence is initiated

14.  This is very specific  Complement proteins (serum proteins) aggregate to initiate an attack on the cell membranes of fungal or bacterial cells  1 st group seals invader

15.  2 nd group punctures wall  3 rd group attaches to the invader to attract leukocytes

16.  T cells:  contain the blue prints for antibodies  They roam the body and search for invaders  signal the attack

17.  Remember : The Macrophages that engulfed bacteria display the antigen on their outer membrane  Helper T then does 2 things:  it activates the killer T cells (these lymphocytes search and destroy)

18.  Helper T cells read the antigen’s shape (the blue print) and release lymphokine  Lymphokine (chemical messenger) targets B cells  The B cells receive the information about the invader

20.  B cells multiply and produce antibodies (weapons)....they display these on their membrane  antibodies : are Y-shaped proteins that bind to specific antigen markers on other cells  Antigens: are protein markers that are found on the cell membranes of most cells

23.  When our antibodies attach to the antigen markers,  they form a antigen-antibody complex  it ties up invaders so they can’t damage our cells

25.  the antigen-antibody complex is really large making it easy to be found by macrophages  Macrophages will engulf and destroy the complex

26.  suppressor T cells inhibit the immune response (stop it)  the immune system makes memory B &T cells  These cells are to recognize the invader if it returns

27.  Macrophages:  any of the large phagocytic cells  some are fixed and some circulate in the blood stream

28.  B-cells – plasma (make antibodies), memory  T-cells – helper, killer, suppressor, memory

29.  Specialized receptor sites are found on the cell membrane of different cells  They are the site which hormones and nutrients enter the cell  Toxins with a similar shape to a hormone or nutrient can attach to the receptor site  It then becomes engulfed by the cell

31.  use receptor sites as entry ports  They inject DNA material into the cell but leave their protein coat at the receptor site  There protein coat enable them to attach to certain cells  E.g. HIV infects T cells