Download 35.2 Nonspecific and Specific Defenses

Chapter 35
The Body’s Defenses
35.1 The Lymphatic System

plasma leaves the blood at capillaries
carries food and picks up waste
 this fluid fills space between cells—called
interstitial fluid
 needs to be returned to the blood


lymph system is a series of tubes
(lymphatic vessels) that return interstitial
fluid to the blood
fluid in lymph vessels is called lymph
 plasma, interstitial fluid, and lymph are the
same juice, different place

Human Lymphatic System
The body’s defenses
35.2 Nonspecific and Specific Defenses
Nonspecific defenses occur
automatically and have no memory

1. barriers to entry
skin
 mucous membranes
 secretions (oil, lysozyme, acid in stomach)

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2. inflammatory response: caused by
physical or chemical damage or pathogens

outward signs (from capillary changes)
 redness
 heat
 swelling
 pain
Cilia in trachea
35.2 Nonspecific and Specific Defenses
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2. inflammatory response, cont.
helps prevent spread of infection
 can inhibit healing if skin is not broken (ice,
ibuprofen, cortisone)
 triggered by damaged tissue cells and mast
cells (WBCs in connective tissues) releasing
histamine
 results in dilation of vessels
 increased permeability
 also triggers fever
 inhibitis microbes
 helps in tissue repair
 facilitates phagocytes
 faster immune cell division

Fig. 35.3 Inflammatory response
Inflammatory response
35.2 Nonspecific and Specific Defenses

3. phagocytes and natural killer cells
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phagocytes
 neutrophils and monocytes: amoeboid,
squeeze through capillaries
 monocytes become macrophages
 dendritic cells (in skin, mucous
membranes) and macrophages (other
tissues)
 recognize pathogens with receptors
 devour pathogens
 release cytokines to stimulate
neutrophils and monocytes
 move through tissue fluid  lymph 
spleen and activate B and T cells
Phagocytosis
35.2 Nonspecific and Specific Defenses
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3. phagocytes and natural killer cells

natural killer cells (NK)
 large, granular
 kill infected (viral) and cancerous body cells
by cell-cell contact
 kill cells without self-proteins; same manner
as cytotoxic T cells
35.2 Nonspecific and Specific Defenses

4. protective proteins
complement (blood plasma proteins)
 amplify inflammatory response
 can bind to pathogens with antibodies,
ensuring phagocytosis
 can form membrane attack complex;
holes cause lysis
 interferons
 produced by virus-infected cells to warn
others
 cause production of substances that
interfere with viral replication in non-infected
cells

35.2 Nonspecific and Specific Defenses
Specific defenses require B-cells and
T-cells

two major cell types:
B cell lymphocytes
 chemical immunity, kill germs using
chemicals (antibodies)
 made in Bone marrow
 T cells lymphocytes
 helper T: control immune system (TH)
 cytotoxic T: kills germs (TC)
 suppresser T: stops immune system when
the attack is over (TS)
 made in Thymus

35.2 Nonspecific and Specific Defenses

two major cell types, cont.
lymphocytes respond to antigens
 antigen (“antibody generating”): foreign
molecule (protein) that elicits a response by
lymphocytes may belong to viruses,
bacteria, fungi, protozoa, parasitic worms,
pollen, transplanted tissue, etc.
 stimulate production of antibodies, which
bind to antigens
 B cells and T cells undergo clonal selection
 there are millions of types of lymphocytes,
each with unique membrane receptors
specific for various antigenic molecules

Clonal selection
35.2 Nonspecific and Specific Defenses
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two major cell types, cont.

B cells and T cells undergo clonal selection
 when an antigen is encountered for the first
time, the lymphocyte attaches to the
receptor complementary to it
 cell with the receptor produces clones of
itself; clones become:
 effector cells (plasma cells)—attack the
antigen (primary immune response
(takes 10-17 days))
 memory cells (last a lifetime)—quickly
attack antigen on 2nd (and later)
exposures (secondary immune
response, AKA immunity)
35.2 Nonspecific and Specific Defenses
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two major cell types, cont.

lymphocytes work by recognizing each other,
invaders, and other body cells with proteins on
their membranes
 major histocompatibility complex (MHC)
 Class I MHC: on all body cells, identifies
cells as being part of the body
 Class II MHC: only on immune cells
 antigens attach to MHC proteins
 B cells have antigen-specific receptors
(similar to antibodies) on their membranes
 T cells have T cell receptors on theirs
 both types of receptors are complementary
to a specific antigen/MHC
Interaction of T cells with MHC molecules
Specific defenses flow chart
35.2 Nonspecific and Specific Defenses
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helper T cells (TH)
immature TH becomes a mature TH
 TH divides producing clones and memory TH
 stimulate B and TC

Role of helper T cells
35.2 Nonspecific and Specific Defenses
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role of TH cells
macrophage surrounds and engulfs antigen
 macrophage begins to “process” the antigen
 processed antigen will be attached to Class II
MHC

35.2 Nonspecific and Specific Defenses
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role of TH cells, cont.
processed antigen on the macrophage is
complementary to TH receptor
 TH and macrophage bind
 interleukins are released by the macrophage
which causes TH to mature

35.2 Nonspecific and Specific Defenses
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cell-mediated immunity
uses cells (TC) to kill eukaryotic cells, including:
 protists and fungi, virus-infected cells,
cancer cells
 steps (for instance):
 antigen enters a body cell and is processed
 after being processed, the antigen is
displayed on a Class I MHC

35.2 Nonspecific and Specific Defenses
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cell-mediated immunity

steps, cont.
 immature cytotoxic T cell binds with
macrophage displaying antigen
 mature helper T-cell attaches to Class II
MHC on macrophage and pumps out
interleukins
35.2 Nonspecific and Specific Defenses
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cell-mediated immunity
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steps, cont.
 interleukins cause cytotoxic T cell to mature
 mature TC binds to infected cell and pumps
out perforin to kill it
Perforin
35.2 Nonspecific and Specific Defenses
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antibody-mediated immunity
kills bacteria and viruses with antibodies
 antibodies:
 cause germs to stick together or precipitate,
easier for macrophages to eat
 inactivate germ (block virus attachment)
 work with the complement proteins to kill the
germ
 are made by B cell lymphocytes

Antibody activity
35.2 Nonspecific and Specific Defenses
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antibody-mediated immunity
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steps:
 a specific B cell binds to an antigen (such
as a virus) by its receptor
 antigen is engulfed
 antigen is processed and the processed
antigen is displayed on the Class II MHC
35.2 Nonspecific and Specific Defenses
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antibody-mediated immunity

steps, cont.
 B cell is now activated and finds a mature
helper T cell, usually at a lymph node or
other lymphatic tissue
 helper T cell releases interleukins which
cause B cell to divide
35.2 Nonspecific and Specific Defenses
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antibody-mediated immunity

steps, cont.
 new B cells are called plasma cells which
mass produce antibodies (30,000
molecules/second!)
 some B cells become memory cells which
wait until next infection (source of immunity)
Immunological memory
AIDS
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human immunodeficiency virus attacks
helper T cells
antibodies are made, but are ineffective
HIV stays dormant for awhile (lysogeny)
until some secondary infection strikes
helper T cells are quickly killed as HIV
spreads, victim loses immunity
Course of HIV-AIDS
Review of specific immunity
Review of specific immunity
Review of specific immunity
Review of specific immunity