The Body’s Three Lines of Defense
First Line of Defense: Physical and Chemical Barriers (6)➢ Non-specific barriers➢ Prevent anything foreign to the body from
penetrating the outer layer of the body➢ Skin, tears, saliva, hair, mucus
membranes, and earwax
The Body’s Three Lines of Defense
Second Line of Defense: White Blood Cells (6)➢ Non-specific➢ If a pathogen penetrates the first line of
defense white blood cells are activated
The Body’s Three Lines of Defense
Third Line of Defense: Specific Resistance (6)➢ Specific➢ Activated when first two lines of defense are
penetrated➢ The body's immune system determines
which antigens are part of its own body structure through the use of marker proteins
➢ When antigens are detected antibodies are produced
➢ T cells and B cells
Causes Cloning of T-Cells
Antigen Fragment
Interleukins
ATP (zap!)
The Concentration of Viruses is too high
Phagocytes and Phagocytosis
➢ Phagocytes: Large white blood cells that eat and digest microbes and other foreign particles (7)○ marker proteins
➢ Work by phagocytosis (type of endocytosis) where the phagocyte engulfs the invading molecules (6)
T(hymus)-Cells (5, 8)
➢ Function is to attack antigens that are on the surface of, or have invaded the body’s cells (pathogens)
➢ Surface of T cells contain specialized antibody-like receptors that can detect pathogens
➢ 2 types, cytotoxic and memory
Helper T-Cells (5)
➢ They are activated on the surface of antigen-presenting cells
➢ Stimulate B-cells to produce antibodies➢ Activate T-cells and B-cells to split and
create more cells ➢ Activate and determine the lifespan of
phagocytes, T-cells, and B-cells
System Video
http://www.pbslearningmedia.org/resource/tdc02.sci.life.stru.immune/immune-cells-in-action/
B-Cells (5)
➢ Secrete antibodies into the body’s fluids➢ Antibodies attack foreign antigens
circulating in the bloodstream➢ Do not penetrate cells➢ Each B-cell is programmed to make one
specific antibody
White Blood Cells
What is a white blood cell?➢ Phagocytes found in the blood stream that
ingest many forms of bacteria and dead cells (2)
➢ Protects the body from disease, cancer, and infection (9)
Antibodies
➢ Proteins produced by B-cells (1)➢ B-cells undergo repeated cell division when
something foreign is detected, forming clones of antibody-secreting plasma cells (3)○ Antibodies bind to the bacteria making
them easier to ingest by white blood cells (3)
Proteins in White Blood Cells
Interleukins: proteins secreted by macrophages (type of white blood cell) that acts as signals for white blood cells to activate when part of the body is infected or destroyed (5)➢ Secreted when a helper T-cell attaches to a
macrophage (5)
Works Cited1. "Antibody." MedLinePlus. MedLinePlus, n.d. Web. 17 Nov. 2014. <http://www.nlm.nih.gov/medlineplus/
ency/article/002223.htm>.2. Dean L. Blood Groups and Red Cell Antigens [Internet]. Bethesda (MD): National Center for Biotechnology
Information (US); 2005. Chapter 1, Blood and the cells it contains. Available from: http://www.ncbi.nlm.nih.gov/books/NBK2263/
3. "How Lymphocytes Produce Antibody." CELLS Alive! Quill Graphics, n.d. Web. 17 Nov. 2014. <http://www.cellsalive.com/antibody.htm>.
4. "Immune Cells and Their Products." National Institute of Allergy and Infectious Diseases. NIH, n.d. Web. 17 Nov. 2014. <http://www.niaid.nih.gov/topics/immunesystem/immunecells/Pages/ default.aspx>.
5. "Immune System." Austin Community College. Austin Community College, n.d. Web. 17 Nov. 2014. <http://www.austincc.edu/apreview/EmphasisItems/Inflammatoryresponse.html>.
6. "Our Internal Defenses." Human Biological Science Unit. WestOne, n.d. Web. 17 Nov. 2014. <http://tle.westone.wa.gov.au/content/file/969144ed-0d3b-fa04-2e88-8b23de2a630c/1/ human_bio_science_3b.zip/content/004_internal_defence/page_01.htm>.
7. "Phagocytes and Their Relatives." National Institute of Allergy and Infectious Diseases. NIH, n.d. Web. 17 Nov. 2014. <http://www.niaid.nih.gov/topics/immunesystem/immunecells/Pages/ phagocytes.aspx>.
8. "Thymus." Encyclopedia Britannica. Encyclopedia Britannica Inc., n.d. Web. 17 Nov. 2014. <http://www.britannica.com/EBchecked/topic/594569/thymus>.
9. "What Are White Blood Cells?" University of Rochester Medical Center. University of Rochester Medical Center, n.d. Web. 17 Nov. 2014. <http://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=160&ContentID=35>.