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THE BODY’S DEFENSE
CHAPTER 43
Figure 43.4 The human lymphatic system
Figure 43.0 Specialized lymphocytes attacking a cancer cell
Figure 43.2 First-line respiratory defenses. Inside the lining of the trachea.
Yellow
cells are
ciliated.
Orange
cells
secrete
mucus.
Figure 43.1 An overview of the body's defenses
NONSPECIFIC DEFENSE
• Skin
• Mucus
• Secretions
CELLS:
Nonspecific
• Neutrophils - engulf microbes
(phagocytosis); self-destruct
after destroy microbes
• Monocytes - develop into
macrophages which can
migrate into tissues and
engulf microbes
Figure 43.x1 Anabaena (a blue-green algae
that makes a toxin, which causes cell death)
phagocytosed by a human neutrophil
Anabaena
Figure 43.3x Macrophage
Figure 43.3 Phagocytosis by a macrophage
Bacilli
Pseudopodia of
macrophage
• Esinophils - destroy parasitic
worms
• Natural killer cells - destroy
viral-infected cells
INFLAMMATORY RESPONSE
• Arterioles dilate to increase
blood flow to damaged area
• Increased WBC in damaged
area
• Histamine and prostaglandins
released to dilate arterioles
• Chemokines - chemical signals
for cells to follow
Figure 43.5 A simplified view of the inflammatory response
SPECIFIC DEFENSE
• Response is to a specific
microbe
• Antigen - foreign molecule
• Antibody - proteins made to
attach to specific antigens
CELLS:Specific
• B lymphocytes - develop in
bone marrow; differentiate
into plasma cells which
secrete antibodies; also make
memory cells
• T lymphocytes - develop in
thymus; activate B cells and
other WBC; also make memory
cells
Figure 43.8 The development of lymphocytes
Figure 43.8x B lymphocyte
Figure 43.6 Clonal selection
• Primary immune response first exposure; 10 - 17 days;
make antibodies
• Secondary immune response already been exposed; 2 - 7
days; memory cells make
antibodies quickly
Figure 43.7 Immunological memory
TOLERANCE FOR SELF
• Major histocompatibility complex
(MHC) on cells
– Class I MHC on all nucleated cells
– Class II MHC on macrophages, B
cells and activated T cells
– Biochemical fingerprint
– As your cells develop, if
fingerprint is wrong then cell
death occurs
– MHC molecules cradle foreign
antigens. They present the
antigen to other cells.
•MHC I presents antigens to
Cytotoxic T cells which kill bad
cells
•MHC II presents antigens to
Helper T cells
– Cells that present antigens are
called antigen presenting cells.
These include macrophages and B
Figure 43.9 The interaction of T cells with MHC molecules
HUMORAL VS. CELL
MEDIATED IMMUNITY
• Humoral - B cells activated by free
antigens (free bacteria, toxins,
viruses)
• Cell mediated - depends on T cells;
active against cells infected with
viruses and bacteria; as well as free
fungi, protozoa, and worms
Figure 43.9 The interaction of T cells with MHC molecules
Figure 43.10 An overview of the immune responses (Layer 4)
T Helper Cells
• Antigen presenting cells
(APC) include B cells and
macrophages
• Present antigen on class II
MHC
• T helper cell binds to MHC II
with antigen
• CD4 on Th cell holds APC cell
and Th cell together
• Th then activates T cytotoxic
cells
• T cytotoxic cells can then lyse
infected cells
Figure 43.11 The central role of helper T cells: a closer look
Figure 43.12a The functioning of cytotoxic T cells
Figure 43.12b A cytotoxic T cell has lysed a cancer cell
ANTIBODY PRODUCTION
• T-dependent antigens - B cell
must be activated by Th cell;
most protein antigens
• T-independent antigens directly stimulate B cells to
make antibodies; mostly
polysaccharide antigens
Figure 43.13 Humoral response to a T-dependent antigen (Layer 3)
ANITBODY MEDIATED
DISPOSAL OF ANITGEN
• Opsonization - many
antibodies bound to antigen
enhance macrophage
phagocytosis
• Agglutination - antibodies
attach to many antigens;
clumping them together to
enhance phagocytosis
Figure 43.16 Effector mechanisms of humoral immunity
ACTIVE IMMUNITY
• Depends on response of
infected person’s immune
system
• May be artificially induced by
vaccinations
Figure 43.x2 Vaccination
PASSIVE IMMUNITY
• Antibodies transferred from
one individual to another
• Some antibodies can move
across placenta to baby in
pregnant women
• Nursing
HEALTH AND DISEASE
• Review ABO blood types and
Rh
• MHC causes tissue and organ
rejections
• In bone marrow transplants,
donated marrow (with WBC)
will react against recipient
• Allergies - overproduction of
certain antibodies causes
histamine to be released
– Runny nose
– Teary eyes
– Smooth muscle contractions
= hard breathing
Figure 43.x4 Alternaria spores, a cause of allergies in humans
• Anaphylactic shock - lifethreatening reaction; abrupt dilation
of arteries causes serious drop in
blood pressure
• Autoimmune diseases - attack own
body
– Lupus, rheumatoid arthritis, MS
• Immunodeficiency Diseases
– Severe combined
immunodeficiency (SCID),
Hodgkin’s
Figure 43.x3 X-ray of hands with arthritis
• AIDS - acquired
immunodeficiency syndrome
– Two major strain: HIV I and
HIV II
– Bind to CD4 and therefore
Th cells
– Insert its RNA and reverse
transcriptase makes viral
DNA that is inserted into
host’s DNA
– Exists as provirus so
antibodies can’t get rid of it
easily
– Mutates often
– May cause Th cell death
– HIV positive = presence of
HIV antibodies
Figure 43.19 A T cell infected with HIV
Figure 43.19x1 HIV on a lymphocyte, detail
Figure 43.20 The stages of HIV infection
Figure 43.x5 AIDS posters