Transcript THE BODY`S DEFENSE

THE BODY’S DEFENSE
CHAPTER 43
Immunity
• Invertebrates have nonspecific
systems
• Plants have molecular recognition of
pathways to defend against
pathogens; leads to destruction of
infected cells
• Vertebrates have nonspecific and
nonheritable defense systems
• Mammals have nonspecific, humoral
and cell mediated.
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.
• Innate immunity is present
before any exposure to
pathogens and is effective from
the time of birth
• It involves nonspecific responses
to pathogens
• Innate immunity consists of
external barriers plus internal
cellular and chemical defenses
• Acquired immunity, or adaptive
immunity, develops after
exposure to agents such as
microbes, toxins, or other
foreign substances
• It involves a very specific
response to pathogens
NONSPECIFIC DEFENSE
• Skin
• Mucus
• Secretions
CELLS:
Nonspecific
• Neutrophils - engulf microbes
(phagocytosis); self-destruct
after destroy microbes
• Macrophages - can migrate into
tissues and engulf microbes
• Esinophils - destroy parasitic
worms
• Natural killer cells - destroy
viral-infected cells
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
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
Fig. 43-8-3
Pathogen
Mast cell
Splinter
Chemical Macrophage
signals
Capillary
Red blood cells Phagocytic cell
Fluid
Phagocytosis
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
(APCs). These include macrophages
and B cells.
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
Fig. 43-16
Humoral (antibody-mediated) immune response
Cell-mediated immune response
Key
Antigen (1st exposure)
+
Engulfed by
Gives rise to
Antigenpresenting cell
+
Stimulates
+
+
B cell
Helper T cell
+
+
Cytotoxic T cell
Memory
Helper T cells
+
+
+
Antigen (2nd exposure)
Plasma cells
Memory B cells
+
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.
Immune System Players
• Antigen presenting cells
(APC) include B cells and
macrophages
• Present antigen on class II
MHC
• T helper cell (Th) 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