Transcript Lecture #19 Date

Chapter 43 ~ The Body’s Defenses
Lines of Defense
Nonspecific Defense Mechanisms……
Phagocytic and Natural Killer Cells
• Neutrophils
60-70% WBCs; engulf and destroy
microbes at infected tissue
• Monocytes
5% WBCs; develop into….
• Macrophages
• Eosinophils
1.5% WBCs; destroy large parasitic
invaders (blood flukes) by enzymatic
hydrolysis
• Natural killer (NK) cells
destroy virus-infected body cells &
abnormal cells
The Inflammatory Response
• 1- Tissue injury; release of chemical signals
– histamine (basophils/mast cells): causes Step 2...
• 2/3- Dilation and increased permeability of capillary
– chemokines: secreted by blood vessel endothelial cells mediates
phagocytotic migration of WBCs
• 4- Phagocytosis of pathogens
– fever & pyrogens: leukocyte-released molecules increase body temp
Specific Immunity
• Lymphocyctes
•pluripotent stem cells...
• B Cells (bone marrow)
• T Cells (thymus)
• Antigen: a foreign molecule that
elicits a response by lymphocytes
(virus, bacteria, fungus, protozoa,
parasitic worms)
• Antibodies: antigen-binding
immunoglobulin, produced by B cells
• Antigen receptors: plasma
membrane receptors on B and T cells
Activating B or T cells
• Effector cells: short-lived cells that combat the antigen
• Memory cells: long-lived cells that bear receptors for the antigen
• Clonal selection: antigen-driven cloning of lymphocytes
Induction of Immune Responses
• Primary immune response: lymphocyte proliferation and differentiation
the 1st time the body is exposed to an antigen
• Plasma cells: antibody-producing effector B-cells
• Secondary immune response: immune response if the individual is
exposed to the same antigen at some later time~ Immunological memory
Self/Nonself Recognition
• Major Histocompatability Complex (MHC): body cell surface antigens
– self genes
• Class I MHC: found on all nucleated cells
• Class II MHC: found on macrophages, B cells, and activated T cells
• Antigen presentation:
– cell displays an intracellular protein to antigen receptor on a nearby T cell
Helper T lymphocytes
• Function in both humoral & cell-mediated immunity
• Stimulated by antigen presenting cells (APCs)
Antibody Structure
• 2 heavy chains and 2 light chains joined by disulfide bridges
• Antigen-binding site (variable region)
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Antibody Function
Neutralization (opsonization): antibody binds to and blocks antigen activity
Agglutination: antigen clumping
Precipitation: cross-linking of soluble antigens
Complement fixation: activation of 20 serum proteins, lyse viruses and
pathogenic cells
Immunity in Health & Disease
• Acquired Immunity
– Conferred immunity by recovering from
disease
– immunization and vaccination; produces a
primary response
• Passive immunity: transfer of immunity
from one individual to another
– natural: mother to fetus; breast milk
– artificial: rabies antibodies
• ABO blood groups (antigen presence)
• Rh factor (blood cell antigen); Rh- mother
vs. an Rh+ fetus (inherited from father)
Abnormal immune function
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Allergies (anaphylactic shock): hypersensitive responses to environmental antigens
Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis, insulindependent diabetes mellitus
Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S.
1. What immune system activities occur in the 1st, 2nd,
3rd lines of defense (primary/secondary/specific
responses)?
2. Describe how histamine works in the inflammatory
response.
3. What are the roles of the different kinds of immune
cells (B cells, helper T, cytotoxic T, macrophages,
memory cells, etc)?
4. What is Rh factor and under what circumstances does
it pose a risk during pregnancy?
5. What immune activities occur at each stage of an
immune response following exposure to a pathogen?
6. How are the ABO blood groups important in
immunity? (what happens if the wrong blood type is
given?)
7. What genetic process enables antibodies to have
variation in their specificity?
8. What is the function of MHC?
9. How does phagocytosis work?
10. How do pathogens evade the second lines of defense?
11. What are antigens? What types of substances can act
as antigens?
12. What mechanisms do pathogens (such as Salmonella)
use to evade the immune system and cause infection?
13. What general activities comprise the overall process of
a specific immune response?
14. What do antibodies do to help fight infection by
pathogens?
15. Distinguish between B and T cells.
16. Compare/contrast autoimmune disease with immune
deficiency disease.
17. How are helper T cells activated?
18. What is clonal selection and what causes it?
19. What is the role of histamine in the inflammatory
response?