Body’s Defenses
• Passive
• Formation of antibodies
• To the fetus thru the placenta, thru breast milk, thru
administration of plasma (artificial)
• Active
• Formation of your own antibodies
• Vaccinations
• by contracting an infectious disease by exposure of an
antigen
Components of the immune system
Innate immune system
Adaptive immune system
Response is non-specific
Pathogen and antigen specific response
Exposure leads to immediate maximal
response
Lag time between exposure and maximal
response
Cell-mediated and humoral components
Cell-mediated and humoral components
No immunological memory
Exposure leads to immunological memory
Found in nearly all forms of life
Found only in jawed vertebrates
• Non-specific
• Specific
•Nonspecific defense
•mechanisms are
general and protect
against many types of
pathogens
•Barriers to entry
•Inflammatory rxns
•Protective proteins
•Pathogens:
•bacteria, fungi, protozoa, and viruses that cause infection
• Physical barriers prevent pathogens such as bacteria and
viruses from entering the organism.
• Enzymes
• Acids: stomach acid
• Complement System
http://www.youtube.com/watch?v=vbWYz9XDtLw
1st WBC to scence
• Phagocytes capable of
diapedesis
• Hallmark of acute
infection
• First to arrive on scene
• 40-70%
• Mediate for allergies
• Limited phagocytic activity
• Strong Chemotaxis
• Attract to injury and infection
• Destroys Antigen/Ab
complex
• 2-4%
•
•
•
•
•
Mast cells
Releases histamine: vasodialator
Heparine: anticoagulant
Releases serotonin/Kinin
.5-1% (smallest population)
• Scavengers
• Transform into macrophages,
eating bacteria, viruses and
tissue debris
• 3rd line of defense
• 3-8%
• Acquired immune response
• SPECIFIC defense system
• 20-25%
• Forms 2 types:
• T cells: attack all foreign cells
• B cells: produce Ab to get rid of
bacteria and viruses
Blood cells are produced in the
bone marrow from a pluripotent
stem cell that can become either a
WBC, RBC or Platelet
http://www.dnatube.com/video/2441/Uptake-of-Bacteria-byPhagocytes
Immunity is a specific defense
mechanism.
It is resistance to a particular
pathogen or its toxin or metabolic byproduct.
Immunity is based upon the ability to
distinguish self molecules from non-self.
Molecules that can elicit an immune
response are antigens.
• The lymphatic system responds to non-self or foreign
antigens, but not to self antigens.
• Shape of antigens allow immune system to be specific
• Antigens: molecules that can elicit an immune response and
each having their own receptor
• may be proteins, polysaccharides, glycoproteins, or glycolipids.
• Macrophages alert
lymphocytes by displaying
antigens from engulfed cells.
• Foreign antigens are
attached to the macrophage
surface by a self protein,
part of the major
histocompatibility complex
(MHC).
• Helper T cells destroy infected cells and clean up pathogens
• T cells attach to foreign, antigen-bearing cells, cell-to-cell
contact.
• Cytokines or lymphokines enhance cellular response to antigens.
• Helper T cells produce chemical signals to activate cytotoxic T
cells, which are WBC carrying pathogen-specific receptors on
their surface
• Kill cancer cells and attack foreign tissue
• Red bone marrow releases
undifferentiated
lymphocytes into the
circulation.
• Some become T
lymphocytes or T cells in
the thymus.
Figure 16.16
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter24/animation__the_immune_respo
nse.html
• B cells secrete antibodies into the blood: antibody-mediated
immunity.
• Helper T cells activate B cells in response to macrophage
presentation of antigens.
• Stimulated B cells produce plasma cells or memory cells.
• Plasma cells produce antibodies.
• AB are released by plasma cells and circulate in blood and
lymph
• Ab attach to pathogens, similar to specific binding of cytotoxic
T cells
• AB/Antigen complex are then destroyed by general defense
like macrophages or proteins that puncture pathogen’s
membranes
• http://bcs.whfreeman.com/thelifewire/content/chp18/1804s.swf
• Helper T cells
• stimulate B cells to produce antibodies
• CD4 cells are prime targets of HIV
• Memory T cells
• produced upon initial antigen exposure and protect against delay in
future exposure
• Cytotoxic T cells
• release perforin to destroy cells that present foreign antigens
• Activated helper T cell
releases cytokines.
• Cytokines stimulate B cell
proliferation.
Figure 16.19
• Some B cells become plasma
cells that secrete antibodies
that bind antigens.
• Antibodies (immunoglobulins)
are globular proteins
composed of four chains.
• Ends of the molecule contain
antigen-binding sites.
• Memory Cells
• Vaccines
• How pathogens evade immunity
• Antigen shifting
• Immunoglobulin G
• IgG, gamma globulin, 80% of
antibodies
• defends against bacteria, viruses, toxins
• found in blood plasma and tissue fluid
• activates complement
Figure 16.20
• Immunoglobulin A
• IgA, 13% of antibodies
• found in exocrine secretions
• defends against bacteria and viruses
• Immunoglobulin M
• IgM, 6% of antibodies, found in plasma
• activates complement
• Immunoglobulin D
• IgD, found on mast cells
• activates B cells
• Immunoglobulin E
• IgE, found in exocrine secretions
• promotes inflammation and allergic reactions
• Antibodies attach directly to antigens
• agglutination, precipitation, neutralization
• Antibodies activate complement
• Combination with antigens exposes reactive sites on complement
which results in
• opsonization increasing phagocytosis susceptibility
• chemotaxis attracting neutrophils and macrophages
• inflammation to prevent spread of antigens
• lysis of cell membranes
• Humoral
• Cellular Barriers
• http://gtmmedia.discoveryeducation.com//downloaddirector/downloadFil
e.aspx?thefile=10053\sec9296_256.mov&realname=The_Imm
une_System