Download Chapter 21 - Immune System

Human A&P
Chapter 21 – The Immune System
Our Defense Systems

Our body has two means of defense against
pathogens and toxins
• Innate or non-specific defenses
– External body membranes
– Internal non-specific defenses
• Adaptive defenses or specific immunity
My Analogy – 3 walls of defense
 Differences:

• Specificity
• Memory
Non-specific Defenses
 External
Barriers (1st Wall)
• Skin and mucous membranes
• Secretions
– lactic acid and fatty acids (skin)
– mucus: filter for respiratory system, etc.
– Tears, lysozyme, stomach acid
• Normal flora
Non-specific Defenses (cont.)
 2nd
wall - Internal Defenses (cells
and chemicals)
• Natural Killer (NK) Cells
• Phagocytes – what cells would this be?
– Figure 21.1
Non-specific Defenses (cont.)

Inflammatory Response (inflammation)
• Signs and symptoms?
• Pathogens and tissue damage stimulate the
release of inflammatory chemicals
– histamine, cytokines, and others
• These result in:
– Vasodilation
– Increased vascular permeability
– Attraction of phagocytes
• Why would this be a good thing?
• Figure 21.3
Non-specific Defenses (cont.)
• Pus and abscesses
 Interferons – anti-viral proteins
• Figure 21.4 and CD animation
Non-specific Defenses (cont.)
 Complement
Proteins - blood proteins
that bind to bacteria and kill them
–Figure 21.5 and CD animation
Non-specific Defenses (cont.)
– pyrogens stimulate an increase in
body temperature
 Fever
• Reading Assignment
Specific Immunity

Final Wall of Defense
• Also called the immune response
• Produced by the B-cells and T-cells

Key features:
• Specificity
– B-cells and T-cells recognize foreign
molecules or antigens (Ag)
• Memory
– they remember which antigens have
entered the body
Specific Immunity (cont.)
– Antibody-generating
substances
 Antigens
• Immunity is all about recognizing self
from non-self
• “if you’re not with us, you’re against
us”
• Figure 21.6 and other figure
Specific Immunity (cont.)
 Activation
of Lymphocytes (B-cells
and T-cells)
• Ag binding to the receptor starts
activation
– A second signal must then be given
• Once the cell is activated it:
– Proliferates and
– Carries out its function
Specific Immunity (cont.)

There are 2 types of responses:
• Cellular or Cell-mediated immunity is
directed against intracellular antigens
– Cytotoxic T-cells
• Humoral or Antibody-mediated immunity is
directed against extracellular antigens
– B-cells
Cell Mediated Immunity
 There
are 2 types of T-cells:
• Activated Cytotoxic T-cells kill virusinfected cells and tumor cells
– Figures 21.16, 21.18, CD animation, and
drawing on board
Cell Mediated Immunity
• Activated Helper T-cells help B-cells
and Cytotoxic T-cells become activated
– They give the 2nd signal
• Figure 21.17
Antibody Mediated Immunity

Antibody Mediated Immunity
• How does a B-cell become activated?
– Ag and Helper T-cells
• Figure 21.17
Antibody Mediated Immunity
• The cell proliferates
• some of the new cells (plasma cells) will
produce antibodies (Ab)
– Ab will bind to the Ag and lead to its
destruction
• some of the new cells will become memory
cells
• Figure 21.9 and AMAZING animation
B-cell Activation
Antigen
B-cell
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
Helper T-cell
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
B-cell Activation
Memory
Cell
Antibody Mediated Immunity
 Memory
• The primary (or 1st) response to an
antigen takes 3-6 days to take effect
• secondary response takes only hours
• Chickenpox example and Figure
21.10
Antibody Mediated Immunity
 Ab
Classes – Table 21. 3
Antibody Mediated Immunity
 Ab
Functions – Figure 21.13
Immunizations
 What
does an immunization do?
 A vaccine is made from antigens that are
not harmful
• Leads to memory
 CD
animation
Allergies
Allergies are an immune response to a
harmless substance
 Hay fever is an allergy to plant pollen

• this usually results in the release of large
amounts of histamine from white blood cells
• histamine triggers inflammation as well as
runny nose, sneezing, etc.
• treated with an antihistamine (it blocks the
effects of histamine)

Anaphylactic shock
Autoimmunity & Transplants
 Autoimmunity
- the immune system
reacting against normal body proteins
• rheumatoid arthritis, others on page 819
 Transplant
Rejection
• Why are transplanted organs or tissues
rejected?
Chapter 21 Readings
 Articles