1. 10.1 The Body’s Lines of Defence
David Vetter ( )
Born with severe combined immunodeficiency (SCID)
SCID is an X-linked disorder, and David’s mother was a carrier
Ten seconds after birth, David was placed in a plastic bubble

2. David Vetter
David needed a germ-free environment, so he had to be inside his bubble for 12 years
Doctors hoped to cure SCID using a bond marrow transplant

3. The Bone Marrow Transplant
October 21, 1983, David received a bone marrow transplant from his sister, Katherine
The marrow contained the Epstein-Barr virus that causes mononucleosis

4. Medical Ethics
While knowing that David would have to live life in a bubble, doctors encouraged his mother to go through with the pregnancy. Some people have said that in this situation, it would have been better to terminate the pregnancy.
What do you think?

5. What was gained?
Doctors now know that SCID can be treated within three months of birth with bone marrow screened for pathogens

6. The Three Lines of Defense
The first and second lines of defense of the human body are nonspecific immune responses
The third line of defense, you immune system, reacts in specialized ways for various invaders

7. The First Line of Defense
Mostly physical
Skin and mucous membranes protect your body
Acidic secretions keep skin at pH of 3-5
Skin has acidic secretions that inhibit the growth of microbes
Lysozyme, an antimicrobial enzyme, is secreted in tears, saliva, mucous and sweat.

8. Respiratory and Digestive System
The respiratory passage is lined with mucous
Cilia also lines the respiratory passage
There is mucous in the respiratory passage that traps invading microbes and other foreign debris with the cilia.
Acids in the stomach and protein digesting enzymes destroy most of the invading microbes carried into the body with food.
Immune System Overview: Goals

9. The Second Line of Defense
Mobilized if an invader resides inside the body
Leukocytes (white blood cells), engulf invading microbes, or produce antibodies
Unlike red blood cells, white blood cells have a nucleus

10. Leukocytes
also called white blood cells are large opaque blood cells that engulf invading microbes. They can also produce antibodies.
They have a nucleus (so different from red blood cells)
The size of the nucleus and the types of granules that can be found inside of them can be used to classify them into different classes of leukocytes.
Granulocytes: have cytoplasmic granules and are made in the bone marrow.
Agranulocytes: do not have a granular cytoplasm and are also made in the bone marrow, but then modified in the lymph nodes.

11. Phagocytosis
Non-specific defense mechanisms rely mainly on phagocytosis
Monocytes migrate from the blood and into the tissues
Macrophages extend pseudopods that grip the invading microbe

13. Neutrophils Attracted to chemical signals emitted by damage microbes
Chemotaxis: A process where the neutrophils exit the capillaries and move toward the damaged tissue
Lysosomal enzymes digest the microbe and the leukocyte
The remaining fragments of protein, dead white blood cells and the digested microbes are called pus

14. Physical Injury
Tissue damage initiates a localized inflammatory response
It is a nonspecific immune response that results in swelling, redness, heat, and pain.
Pus and inflammation are signs that the second line of defence has been at work.

16. System Wide Defense
Injured cells emit chemicals that stimulate the production of phagocytic white blood cells, red blood cells and lymphocytes from the bone marrow

17. Fever is another example of the body’s response to infection.
When you have infectious organisms in your body, neutrophils and macrophages digest the invaders and release chemicals into the bloodstream
When the chemicals reach the hypothalamus, they reset your body temperature to 40C in order to make it difficult for the bacteria to survive.