Transcript A P Chapter 12 PowerPoint Part B

The Lymphatic System and
Body Defenses
Chapter 12 Part B
Defense Systems of the Body--Quick Review
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1st Line:
 Surface membrane barrier
 Secretions
2nd Line:
 Defensive cells: Phagocytic & Natural Killer Cells
 Antimicrobial Proteins
 Inflammatory Response & Fever
Defense Systems of the Body--Quick Review
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3rd Line:
 Antigen specific – recognizes and acts against
particular foreign substances
 Systemic – not restricted to the initial
infection site
 Has memory – recognizes and mounts a
stronger attack on previously encountered
pathogens
Video Clip: Innate & Adaptive Immunity
Adaptive Defense System –Third Line of
Defense
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Types of Immunity:
Humoral (fluid) immunity = Antibodymediated immunity
 Provided by antibodies present in body fluids
 Cells produce chemicals for defense
Cellular immunity = Cell-mediated immunity
 Cells target virus infected cells, cancer cells, and
cells of foreign grafts
 Lymphs directly lyse foreign cells or release
chemicals that increase inflammatory response
Adaptive Defense System--Third Line of
Defense
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Antigens (nonself)
 Any substance capable of exciting the immune
system and provoking an immune response
 Examples of common antigens:
 Foreign proteins (strongest)
 Nucleic acids
 Large carbohydrates
 Some lipids
 Pollen grains
 Microorganisms
Adaptive Defense System: Third Line of
Defense
 Self-antigens
Human cells have many surface proteins
 Our immune cells do not attack our own
proteins
 Our cells in another person’s body can
trigger an immune response because they are
foreign
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Restricts donors for transplants
Adaptive Defense Systems: Third Line of
Defense
 Allergies
Many small molecules (called haptens or
incomplete antigens) are not antigenic, but link
up with our own proteins
 The immune system may recognize and
respond to a protein-hapten combination
 The immune response is harmful, rather than
protective, because it attacks our own cells
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Common Allergies
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Poison ivy
Animal dander
Detergents
Hair dyes
Penicillin
Adaptive Defense System: Third Line of
Defense
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Cells of the adaptive defense system:
 Lymphocytes respond to specific antigens
 B lymphocytes (B cells)
 T lymphocytes (T cells)
 Macrophages help lymphocytes
 Immunocompetent—cell becomes capable of
responding to a specific antigen by binding to it
Adaptive Defense System: Cells
Lymphocytes:
 Originate from hemocytoblasts in the red
bone marrow
 B lymphocytes become immunocompetent
in the bone marrow ( B = Bone marrow)
 T lymphocytes become immunocompetent
in the thymus (T = Thymus)
Video Clip: Types of White Blood Cells
Lymphocyte Differentiation and Activation
Lymphocytes destined to become T cells
migrate from bone marrow to the thymus
and develop immunocompetence there.
B cells develop immuno-competence in
the bone marrow.
Bone marrow
Circulation
in blood
Thymus
Immature
lymphocytes
Bone marrow
KEY:
Site of lymphocyte origin
and
Sites of development of
immunocompetence as B
or T cells; primary lymphoid organs
Site of antigen challenge and final
differentiation to mature B and T cells
Figure 12.11, step 1b
Lymphocyte Differentiation and Activation
Lymphocytes destined to become T cells
migrate from bone marrow to the thymus
and develop immunocompetence there.
B cells develop immuno-competence in
the bone marrow.
Bone marrow
Circulation
in blood
Thymus
Immunocompetent,
but still naive,
lymphocytes
migrate via blood
Immature
lymphocytes
After leaving the thymus or bone marrow
as naive immunocompetent cells,
lymphocytes “seed” the infected
connective tissues (especially lymphoid
tissue in the lymph nodes), where the
antigen challenge occurs and the
lymphocytes become fully activated.
Bone marrow
Lymph nodes
and other
lymphoid tissues
KEY:
Site of lymphocyte origin
and
Sites of development of
immunocompetence as B
or T cells; primary lymphoid organs
Site of antigen challenge and final
differentiation to mature B and T cells
Figure 12.11, step 2
Lymphocyte Differentiation and Activation
Lymphocytes destined to become T cells
migrate from bone marrow to the thymus
and develop immunocompetence there.
B cells develop immuno-competence in
the bone marrow.
Bone marrow
Circulation
in blood
Immature
lymphocytes
After leaving the thymus or bone marrow
as naive immunocompetent cells,
lymphocytes “seed” the infected
connective tissues (especially lymphoid
tissue in the lymph nodes), where the
antigen challenge occurs and the
lymphocytes become fully activated.
Thymus
Bone marrow
Immunocompetent,
but still naive,
lymphocytes
migrate via blood
Mature
immunocompetent
B and T cells
recirculate in
blood and lymph
Activated (mature) lymphocytes circulate
continuously in the bloodstream and
lymph, and throughout the lymphoid
organs of the body.
Lymph nodes
and other
lymphoid tissues
KEY:
Site of lymphocyte origin
and
Sites of development of
immunocompetence as B
or T cells; primary lymphoid organs
Site of antigen challenge and final
differentiation to mature B and T cells
Figure 12.11, step 3
Adaptive Defense System: Cells
Macrophages
 Arise from monocytes
 Become widely
distributed in lymphoid
organs
 Secrete cytokines
(proteins important in
the immune response)
 Tend to remain fixed in
the lymphoid organs
Functions of Cells & Molecules Involved in Immunity
Table 12.3 (2 of 2)
Humoral (Antibody-Mediated) Immune
Response
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Video Clip: Humoral Immunity
B lymphocytes with specific receptors bind to a specific antigen
The binding event activates the lymphocyte to undergo clonal
selection
A large number of clones are produced (primary humoral
response)
Most B cells become plasma cells
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Produce antibodies to destroy antigens (2000 abs/second)
Activity lasts for four or five days, then plasma cell dies
Ab level peaks at 10 days & then declines
Some B cells become long-lived memory cells (secondary
humoral response)
Humoral Immune Response
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Secondary humoral responses:
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Memory cells are long-lived
A second exposure causes a rapid response
The secondary response is stronger and longer lasting
Abs peak at 2-3 days, remains high for weeks to months
Humoral Immune Response
Humoral Immune Response:
Primary v. Secondary Response
Figure 12.13
Brain Break!!!
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Sci Fives!!
Active Immunity
 Occurs
when B cells encounter antigens
and produce antibodies
 Active immunity can be:
naturally acquired during bacterial and viral
infections
 artificially acquired from vaccines
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Vaccines: pneumonia, smallpox, polio, tetanus, etc.
Figure 12.14
Passive Immunity
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Occurs when antibodies are obtained from someone else
 Conferred naturally from a mother to her fetus (naturally
acquired)
 Conferred artificially from immune serum or gamma globulin
(artificially acquired)
 Used because disease would kill before active immunity
develops
 Exposure to hepatitis
 Anti-venom for snake bites
 Antitoxin for botulism, rabies & tetanus
Short lived immunity
Immunological memory does not occur
Protection provided by “borrowed antibodies”
Passive Immunity
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Monoclonal antibodies
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Antibodies prepared for clinical testing or diagnostic services
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Cancer-fighting drugs
Produced from descendents of a single cell line
Examples of uses for monoclonal antibodies:
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Diagnosis of pregnancy
Treatment after exposure to hepatitis and rabies
Summary: Types of Acquired Immunity
Figure 12.14
Brain Break
Antibodies (Immunoglobulins) (Igs)
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What IS an antibody, anyway???
Soluble proteins secreted by B cells (plasma cells)
Carried in blood plasma
Capable of binding specifically to an antigen
Five classes, based on structure & function:
IgM, IgA, IgD, IgG, IgE
Figure 12.15a
Antibody Structure
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Four amino acid chains
linked by disulfide bonds
Two identical amino acid
chains are linked to form a
heavy chain; made of about
400 amino acids each
The other two identical
chains are light chains
Specific antigen-binding sites
are present at the variable
end of each chain
Video Clip: (15) Antibody Structure
Figure 12.15b
Antibody Classes
Antibodies of each class have slightly different
roles
 Five major immunoglobulin classes (MADGE)
 IgM – largest of the antibodies; can fix
complement
 IgA – found mainly in mucus; prevent
pathogens from entering body
 IgD – important in activation of B cell
 IgG – can cross the placental barrier; most
abundant; can fix complement
 IgE – involved in allergy repsonse
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Table 12.2
Video Clip: (16) Antibody Function
Antibody Function
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Antibodies inactivate antigens in a number of ways:
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Complement fixation – causes lysis of cell
Neutralization- abs bind bacterial exotoxins & viruses to
block harmful effects
Agglutination- as in rbcs
Precipitation- soluble ag complex precipitates out & engulfed
by phagocytes
Antibody Function
Figure 12.16
Cellular (Cell-Mediated) Immune Response
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Antigens must be presented by macrophages to an
immunocompetent T cell (antigen presentation)
T cells must recognize nonself and self (double
recognition)
After antigen binding, clones form as with B cells, but
different classes of cells are produced
Cellular (Cell-Mediated) Immune Response
Figure 12.17
T Cell Clones
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Cytotoxic T cells
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Helper T cells
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Recruit other cells to fight the invaders
Interact directly with B cells, causing rapid division
Release cytokines, chemicals that enhance immune response
Regulatory T cells
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Specialize in killing infected cells
Insert perforin(a toxic chemical) into foreign cell membrane
Release chemicals to suppress the activity of T and B cells
Prevents uncontrolled activity
A few members of each clone are memory cells
Video Clip: T Cells
Cellular
(Cell-Mediated)
Immune
Response
Functions of Cells and Molecules
Involved in Immunity
Table 12.3 (1 of 2)
Functions of Cells and Molecules
Involved in Immunity
Table 12.3 (2 of 2)
Summary of Adaptive Immune Response
Figure 12.19 (1 of 2)
Summary of Adaptive Immune Response