body’s defenses. passive formation of antibodies to the fetus thru the placenta, thru breast milk,...
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Immune Responses
• 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
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
Components of the immune system
Types of Defenses
•Nonspecific defense
• mechanisms are general and protect against many types of pathogens
• Barriers to entry
• Inflammatory rxns
• Protective proteins
Types of Defenses: non-specific
•Pathogens: • bacteria, fungi, protozoa, and viruses that cause
infection
Layered Defenses• Physical barriers prevent pathogens such as
bacteria and viruses from entering the organism.
Chemical Barriers• Complement System
http://www.youtube.com/watch?v=vbWYz9XDtLw
Neutrophils1st WBC to
scence• Phagocytes
capable of diapedesis
• Hallmark of acute infection
• First to arrive on scene
• 40-70%
Eosinophils
• Mediate for allergies• Limited phagocytic
activity• Strong Chemotaxis
• Attract to injury and infection
• Destroys Antigen/Ab complex
• 2-4%
Basophils
• Mast cells• Releases histamine:
vasodialator• Heparine: anticoagulant• Releases serotonin/Kinin• .5-1% (smallest
population)
Monocytes
• Scavengers• Transform into
macrophages, eating bacteria, viruses and tissue debris
• 3rd line of defense• 3-8%
Lymphocytes
• 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-by-Phagocytes
Specific DefensesImmunity is a specific defense mechanism.
It is resistance to a particular pathogen or its toxin or metabolic by-product.
Immunity is based upon the ability to distinguish self molecules from non-self.
Molecules that can elicit an immune response are antigens.
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.
Antigen-Presenting Cells• 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).
Cellular Immune Response• 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
Lymphocytes Origin• Red bone marrow
releases undifferentiated lymphocytes into the circulation.
• Some become T lymphocytes or T cells in the thymus.
Figure 16.16
The Immune Response
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter24/animation__the_immune_response.html
Humoral ImmunityRemoving Pathogens at large
• 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
Types of T Cells• 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
B Cell Activation
• Activated helper T cell releases cytokines.
• Cytokines stimulate B cell proliferation.
Figure 16.19
B Cell Activation• 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.
Immunoglobulins
• 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
Immunoglobulins• Immunoglobulin A
• IgA, 13% of antibodies• found in exocrine secretions• defends against bacteria and
viruses
Immunoglobulins• 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
Antibody Actions
• 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
• http://gtm-media.discoveryeducation.com//downloaddirector/downloadFile.aspx?thefile=10053\sec9296_256.mov&realname=The_Immune_System