The Immune System
Tucker, Kathy, Hunter, Brielle
Functions
● Scavenge dead or dying body cells
● Destroy abnormal/cancerous cells
● Protect from foreign molecules
(bacteria, viruses)
3 Lines of Defense
• Chemical and physical barriers
• Nonspecific Resistance
• Specific Resistance
Physical Barriers
First line of defense
○ Skin: thick layer of dead cells
○ Mucous membranes that trap microbes
○ Hair in the nose that traps dust and pollutants
○ Cilia: small hairs that trap pollutants
○ Urine
○ Vomiting
(Allied health)
Chemical Barriers
First line of defense
● Antibiotic lysozyme enzyme: in tears and sweat
● Gastric juice--acidity destroys bacteria and toxins
● Saliva washes mouth and teeth
● Acid on the surface of the skin
● Sebum: oily secretion of glands
● Hyaluronic acid: viscous fluid
(Allied Health)
Nonspecific Resistance
Second line of defense: destroys invaders in a generalized way that does
not target specific individuals
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Inflammation brings more white blood cells to site where microbes have invaded
Fever inhibits bacterial growth
Phagocytic/macrophage (cells) destroy microbes that pass into body tissues
○ Phagocyte attaches to microbe
○ Phagocytes plasma membrane surrounds microbe and takes it into the cell in a vesicle
○ Vesicle merges with a lysosome
○ Digestive enzymes break down microbe --> phagocyte uses microbe’s nutrients
○ Phagocyte produces protein markers that enter the vesicle
○ Indigestible material is removed in exocytosis
○ Antigenic fragments bind to protein markers and are displayed on plasma membrane
surface
○ Phagocyte secretes interleukin 1
Phagocyte destroying Microbe
Overview
Specific Resistance
Third line of defense: when nonspecific methods are not enough and
infection becomes widespread
● Steps for an immune response using lymphocytes (helper T-cells):
○ When an antigen is detected by a macrophage (nonspecific resistance),
the interleukin 1 activates helper T-cells
○ The body has millions of different helper T-cells all able to respond to one
specific antigen...similar to enzymes and specificity!
○ Helper T-cells bind to the marker proteins and secrete interleukin 2
which causes the cytotoxic T-cells and B-cells to be made rapidly
○ From here, the response can take 2 paths: one with cytotoxic T-cells and
the other with B-cells …
(Starr, Taggart)
Cytotoxic T-cells
Involved in third line of defense
○ The “killer” cell
○ T-cell function: to destroy the pathogen in the infected body and tumor
cells
○ T-cells arise from stem cells in the bone marrow
○ T-cells recognize antigens on surface of infected body cells
○ Bind to infected surface and secrete cytotoxins that induce apoptosis
(cell suicide) and perforins that cause punctures and holes in the
infected cells
○ This is called cell-mediated immunity
(Nobel Prize)
B-cells
Involved in third line of defense (B-cell pathway)
○ Helper T-cells stimulate B-cells to divide, forming plasma cells
that produce antibodies and memory B-cells
○ If the same antigen enters the body again, the memory B-cells
react quickly by making more specific antibodies to fight against
the recognized attack
○ The antibodies circulate through the bloodstream and bind to
specific antigens, attacking and killing the present microbe
○ This is called antibody-mediated immunity
(Nobel Prize)
Entire Process
antibody-mediated
immunity
http://www.austincc.edu/apreview/EmphasisItems/Inflammatoryresponse.html#top
Fun Facts
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The term "antigen" comes from ANTI-body GENerating substances (Allied
Health)
● Getting under 5 hours of sleep a night depresses your immune system
● People who lack humor in their lives tend to have less protective immune
responses
● In your blood, there are around 50 billion white blood cells
● Dieting decreases natural killer cell functionality, therefore weakening the
immune system.
● While the body needs some sunlight to produce vitamin D, too much
sunshine can suppress the immune system
(Sisson)
Recap
Definitions
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White Blood Cell: any of the various blood cells that help prevent disease
Phagocyte/macrophage: a cell that engulfs and consumes foreign
organisms
Cytotoxic T-Cells: white blood cell known as “killer cell”
B-Cells: white blood cell that produces antibodies
Helper T-Cells/lymphocytes: T-cell that controls the activity of other white
blood cells
Pathogen/microbe: bacteria, virus or other microorganism that causes
disease
Antigen: a toxin that induces an immune response in the body
Antibody: a blood protein that counteracts a specific antigen
Interleukin 1 and 2: secreted proteins in an immune response
References
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Allied Health Educational Grant Program. "Immune System." Associate Degree
Nursing Physiology Review. Ed. Austin Community College. N.p., Aug. 2008. Web. 30 Oct.
2013. <http://www.austincc.edu/apreview/EmphasisItems/Inflamm
atoryresponse.html#top>.
"The Immune System - in More Detail". Nobelprize.org. Nobel Media AB 2013. Web.
31 Oct 2013. <http://www.nobelprize.org/educational/medicine/immunity/immune
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-detail.html>
National Institutes of Health. "Immune System." National Institute for Allergy and
Infectious Disease. Ed. U.S. Department of Health and Human Services. U.S.
Department of Health and Human Services, 23 Oct. 2013. Web. 30 Oct. 2013.
<http://www.niaid.nih.gov/topics/immuneSystem/Pages/default.aspx>.
Sisson, Mark. "10 Things You (Likely) Don’t Know About Your Immune System." Marks Daily
Apple. 19 Aug. 2013. 03 Nov. 2013 <http://www.marksdailyapple.com/10-things-youlikely-dont-know-about-your-immune-system/>.
Starr, Cecie, and Ralph Taggart. "Immunity." Biology: The Unity and Diversity of Life.
Pacific Grove: Jack c. Cary, 2001. 690-703. Print.