Transcript CD4: Helper T cell surface protein

Figure 43.0 Specialized lymphocytes attacking a cancer cell
The Body’s Defense: The Immune System
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A lymphocyte: They display specificity for an antigen
There are:
B lymphocytes or cells and
T lymphocytes or cells
They display:
Specificity
Diversity
Memory
Can distinguish self from nonself
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Figure 43.1 An overview of the body's defenses
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Nonspecific Defenses
1. Skin
a) Oil and sweat glands keep pH about 3-5 and this prevents
bacteria from inhabiting the area.
b) Lysozyme: an example of a protein that digests bacterial
cell walls.
Found in eyes, upper respiratory tract.
2. Mucous
a) traps bacteria in respir. tract
b) action of cilia
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3. Action of neutrophils
a) phagocytes
b) exhibit a chemotaxis: attracted by chemicals released by
damaged cells
4. Monocytes
a) develop into macrophages that will engulf bacteria
b) attracted to the polysaccharides on the bacteria’s surface.
c) engulfed into a vacuole and then nitric oxide (NO) will
destroy it.
5. Natural Killer Cells
a) attack virus-infected cells and cause the cells to lyse
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Figure 43.3 Phagocytosis by a macrophage
Bacteria are the rodshaped structures
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Figure 43.3x Macrophage
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The Importance of the Lymph Nodes
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The Inflammatory Response
Pyrogens
Complement system: bunches of proteins
Interferons: released by virus-infected cells
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Figure 43.6 Clonal selection
Selected B cell makes clones
Antigen receptors are actually membrane antibodies or immunoglobulins
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Immune Response: Know this well
Primary Immune
Response
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Figure 43.10 An overview of the immune responses (Layer 2)
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Figure 43.8 The development B and T Cells or lymphocytes
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Figure 43.9 The interaction of T cells with MHC molecules
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Major Histocompatibility Complex (MHC)
1. There are genes that code for two types of distinguishing
glycoproteins on a cell’s surface:
a) Class I MHC
b) Class II MHC
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2. The Role of the MHC Glycoproteins
a) Antigen Presentation
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Figure 43.10 An overview of the immune responses (Layer 4)
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Figure 43.11 The central role of helper T cells: a closer look
TH cells: involved in both cell
mediated and humoral responses.
CD4: Helper T cell surface protein:
binds to the presented antigen fragment
of the APC
Upon activation by the APC, the TH cells
will make many clones and also produce
memory TH cells.
Once activated, a macrophage
will make IL-1 which helps to
make IL-2 which stimulates TH
cells to divide as well as the
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production of B cells
Figure 43.12a The functioning of cytotoxic T cells
MHC I Glycoprotein: all nucleated
cells
Tumor Cells: present tumor
antigens to Tc cells so the body can
fight against tumors
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Figure 43.12b A cytotoxic T cell has lysed a cancer cell
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Figure 43.13 Humoral response to a T-dependent antigen (Layer 3)
B cells can be
stimulated by TH cells
to make antibodies.
This is a T- dependent
antigen.
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Figure 43.10 An overview of the immune responses (Layer 2)
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Figure 43.11 The central role of helper T cells: a closer look
TH cells: involved in both cell
mediated and humoral responses.
CD4: Helper T cell surface protein:
binds to the presented antigen fragment
of the APC
Upon activation by the APC, the TH cells
will make many clones and also produce
memory TH cells.
Once activated, a macrophage
will make IL-1 which helps to
make IL-2 which stimulates TH
cells to divide as well as the
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production of B cells
Epitopes (antigenic determinants)
Epitopes: small portion of an antigen to which the
antibody binds.
Epitope B
Epitope C
Epitope A
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Figure 43.15a,b The structure of a typical antibody molecule
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Fig. 43-13
DNA of undifferentiated B cell
V37
V38
V39
V40
J1 J2 J3 J4 J5 Intron
C
1 DNA deleted between randomly selected V and J
segments
DNA of differentiated B cell
V37
V38
V39 J5
Intron
C
Recombinase acts
randomly to combine any
one of the J gene segments
with any one of the V gene
segments.
Functional gene
2 Transcription
pre-mRNA
V39 J5
C
Intron
3 RNA processing
mRNA
Cap
V39 J5
C
40V x 5J x 1C = 200
different ways.
B cell receptor
Poly-A tail
V
V
V
4 Translation
V
C
C
Light-chain polypeptide
V
Variable
region
C
C
Constant
region
B cell
C
Figure 43.15c Antibody molecule
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Table 43.1 The Five Classes of Immunoglobulins
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Figure 43.16 Effector mechanisms of humoral immunity
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Figure 43.17 The classical complement pathway, resulting in lysis of a target cell
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Types of Immunity
1. Active Immunity
a) naturally acquired after an infection (chicken pox)
b) acquired by an immunization (vaccination)
c) person demonstrates the secondary response
2. Passive Immunity
a) antibodies acquired from another person
b) antibodies are passed from a mother’s breast milk to
nursing child while the child’s immune system is
developing.
c) a rabies bitten person can receive antibodies from those
vaccinated against rabies
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Allergic Reactions
1. An allergen causes a specific kind of antibody IgE to be
released from plasma cells and instead of binding to the
allergen (pollen) they bind to mast cells that are present in
connective tissue (ligaments, tendons, etc).
2. This causes the mast cells to release histamine
3. Histamine causes blood vessels to dilate and also increases
their permeability so lots of fluid leaks out.
4. Antihistamine
5. Anaphylactic shock: allergic response is one of huge release
of histamine and so much blood goes to periphery that blood
pressure drops.
(bee stings, food allergies (peanuts)
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Person takes a shot of epinephrine.
Figure 43.18 Mast cells, IgE, and the allergic response
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Figure 43.x4 Alternaria spores, a cause of allergies in humans
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Figure 43.19 A T cell infected with HIV
T cell
Viruses: small blue
dots
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Figure 43.19x2 HIV budding
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Figure 43.19x2a T cell infected with HIV
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Figure 43.20 The stages of HIV infection
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HIV MOLECULAR BIOLOGY
1.
Retrovirus
2.
Several strains of HIV
3.
Binding and Entry
a)
RNA has 9 different genes encoding 15 proteins.
b)
Entry requires the fusion of the viral envelope with the host cell
membrane.
c)
The viral envelope interacts with specfic cell surface receptors.
d)
gp120 is on the viral surface binds to the CD4 receptors on the T
cells.
e)
gp41
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Virus attacks cells with CD4 receptors on TH cells(immune system cells)
5.
Role of TH cells? Stimulates the immune system; they bind to MHC II
APC’s which stimulates both cell mediated immunity and antibody
secretion from plasma cells
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6.
HIV binds to probably several proteins: CD4 receptor, a fusin
protein which allows for the envelope of the virus to join with
the T cell and another receptor CCR5 which is on
macrophages.
7.
8.
CXCR4 binds to T-cells in later stages of the disease.
In up to 13% of individualos of northern Eurpean descent, a
naturally occurring deletion of 32 base pairs in the CCR5 gene
results in a mutant CCR5 receptor that never reaches the cell
surface.
a)
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10.
Individuals homozygous for this mutation (1-2% of Caucasian
population) are almost completely resistant to HIV infection.
Binding of gp120 and CD4 produces changes in gp41, it springs
open and grabs the lipid bilayer of the target cell. This
promotes fusion.
Detection for HIV antibodies: 1-12 months after
exposure/infection.
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