Term
| Pathogens that elicit defense responses |
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Definition
bacteria
viruses
fungi
protozoa
worms |
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Term
| Nonpathogenic foreign substances that alert defenses |
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Definition
pollen
chemicals
transplanted tissue |
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Term
| Dead or damaged cells that are cleared away by some of the defense systems |
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Definition
injured tissues
old red blood cells
abnormal cells may also be attacked |
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Term
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Definition
| They are not keyed to individual pathogens, and there is no clonal selection. |
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Term
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Definition
| They are keyed to individual pathogens, they adapt to specific pathogens, and there is clonal selection |
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Term
| Innate defenses: Barriers |
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Definition
skin, mucus membrane
skin - low pH - inhospitable to most bacteria |
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Term
| Innate defenses: phagocytes |
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Definition
| (cell eaters) such as macrophages. Enter tissues from the blood and eat invaders and assorted debris |
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Term
| How do phagocytes recognize enemies? |
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Definition
| By direct interaction with molecules on the surface of the target, or by interaction with a label attached to the target by the host's system - opsonization |
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Term
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Definition
interaction with a label attached to the target by the host's system
anitbodies
complement proteins
acute phase proteins |
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Term
| What is the main way phagocytes kill target cells? |
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Definition
phagocytosis - a phagosome carries the target into the phagocyte and fuses with a lysosome.
Active phagocytes can also signal and recruit other defenses to help |
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Term
| How does an active phagocyte signal and recruit other defenses? |
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Definition
two ways
- by release of signalling molecules (cytokines)
- by antigen presentation on cell surface |
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Term
| Natural killer (NK) cells |
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Definition
can attack cancerous cells and cells infected with viruses
early-acting defense if there is an infection |
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Term
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Definition
| by the release of granules containing proteins that destroy the target cell membrane, proteolytic enzymes that chew up the target's proteins, and molecules that induce target cell suicide (apoptosis) |
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Term
| How do NK cells recognize infected cells? |
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Definition
| unusual molecules on the surface of the target cell; both infected cells and tumour cells display their status on their surface |
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Term
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Definition
| cytokines - proteins secreted by immune system cells (helper T cells, macrophages) that regulate the activities of nearby cells. Among their effects, they can induce anti-viral defenses in target cells |
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Term
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Definition
| consists of 30 blood serum proteins that can destroy the membrane of a foreign cell or opsonize an invader, attracting macrophages |
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Term
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Definition
| response to tissue damage, either internal or external, that mainly handles bacterial infections |
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Term
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Definition
| The body's thermostat is reset upwards after infection. The higher temperature inhibits growth of the pathogen, and speeds up the action of defensive cells. |
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Term
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Definition
| signalling molecules that tell the hypothalamus to raise its setpoint |
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Term
| Specificity of adaptive defenses |
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Definition
| each defensive molecule (antibody, T cell receptor) interacts with a specific part of a target molecule (antigen) |
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Term
| Diversity of adaptive defenses |
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Definition
| The system as a whole interacts with many different antigens (millions) |
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Term
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Definition
| The system can distinguish between foreign and domestic molecules, except in pathological cases |
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Term
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Definition
| The system recalls antigens it has seen in the past |
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Term
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Definition
An individual molecule which manifests the properties of specificity and diversity
Two regions:
variable region - different in each
constant region - the same in lg class |
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Term
| immunoglobulin (lg) class |
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Definition
| a set of similar antibodies |
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Term
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Definition
part of the antigenic molecule that binds the antibody
12-20 amino acids |
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Term
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Definition
Proteins
Glycoproteins
Polysaccharides
Glycolipids |
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Term
| How are millions of different antibodies (with millions of different specificities) generated? |
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Definition
| By the editing of genes during the development of B cells, the cells that produce antibodies. The lg genes are randomly and independently mutated in each developing B cell |
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Term
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Definition
Manifest specificity and deiversity
Bind to antigens
Their diversity is generated by gene rearrangements |
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Term
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Definition
derives from stem cells in bone marrow
B lymphocytes (B cells) - mature in the bone marrow
T lymphocytes (T cells) - mature in the thymus |
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Term
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Definition
have antibodies on their surface that serve as antigen receptors, telling the B cells that if there is an antigen our there with the specificity to bind to that antibody
All the antibodies on the surface of a given B cell will have the same specificity; another B cell will have antibodies on its surface with a different specificity
activated by antigen binding or by interaction with a helper T cell |
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Term
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Definition
| Two B cell clones result from the activation of a single B cell with a single antigenic specificity |
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Term
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Definition
Type of B cell; short lived
secretes antibodies of the same specificity as the B cell receptor |
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Term
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Definition
Type of B cell; long lived
no immediate role but potentiates later responses |
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Term
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Definition
serve as membrane bound receptors in B cells
Coat viruses and bacteria, preventing attachment to epithelia
coat cells, viruses and particles for macrophage attack
activate complement |
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Term
| T lymphocytes: helper T cells |
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Definition
Helper T cells provide links between macrophages, dendritic cells, humoural immunity and cell-mediated immunity.
Macrophages and dendritic cells are antigen-presenting cells (APCs). A major histocompatibility complex (MHC) molecule presents the antigen to Th cells
An activated helper T cell in turn will activate B cells and cytotoxic T cells |
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Term
| T lymphocytes: cytotoxic T cells |
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Definition
Activated by Th cells and infected cells (eg with a virus AKA killer T cells)
Tc cell will lyse the membrane of the target cell
A line of memory T cells is established too, as with B cells |
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Term
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Definition
the secondary response to an antigen is faster and greater than the primary one
this is the basis of acquired immunity |
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Term
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Definition
antibodies are supplied directly from the outside
eg antibodies are transferred across the placenta, protects the fetus |
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Term
| For each of the following, state whether they belong to the adaptive or the innate defense system, and state why: plasma cells, macrophages, antibodies, memory B cells, complement, inflammation |
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Definition
plasma cells - adaptive; produce only one kind of antibody recognizing only one epitope
macrophages - innate; recognize general features of bacteria or infected cells
antibodies - adaptive; recognize only one epitope
memory B cells - adaptive; descended from a B cell that produced only one kind of antibody
complement - innate; able to bind directly to many kinds of bacteria and to the constant region of antibodies
inflammation - innate; a wound introducing any pathogen will send out chemical signals that cause vasodilation, bringing phagocytes to the infected area |
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Term
| In what cases do the adaptive and innate defense systems cooperate? |
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Definition
| Macrophages and dendritic cells present antigens (bound to Class II MHC proteins) to helper T cells, thus activating them. Antibodies coat an invading cell or toxin and invite attack by macrophages. Antibodies help complement proteins recognize invading cells and lyse them. Natural killer cells can recognize an antibody-coated invader, and proceed to lyse the plasma membrane of that invader |
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Term
| What are the differences between humoural and cell-mediated immunity? What cell type stimulates both systems? |
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Definition
| Humoural immunity comprises the antibodies secreted by plasma cells. Cell-mediated immunity is the direct killer of infected cells by cytotoxis T cells. The link between the two branched is the helper T cell, which stimulates both |
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Term
| In the film Fantastic Voyage a team of medical adventurers allow themselves to be shrunken to microscopic size and injected into the blood of a patient in order to do some microsurgery on him. One of the characters gets covered with antibodies while swimming around in his serum. The film was made in the 1960s when the structure and function of antibodies were not understood as well as they are today. As a consequence, the film showed this character suffering grave distress, but did not make it clear how, exactly, the antibodies were causing the distress. What might the antibodies have been doing to her? |
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Definition
The coating of her body may have invited attack by macrophages
(although things did not come to that pass in the movie). More likely,
complement proteins might have discovered the antibody sticking to her
and begun lysing her membranes (not shown either, although the
connection between antibodies and complement attack had been
demonstrated as far back as 1898). |
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Term
| How is the great variability of antibodies generated? |
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Definition
By a rearrangement and editing of the genes encoding the variable (V)
and junction (J) regions immunoglobulin molecules. A given lymphocyte
has several choices in picking the V and J regions for inclusion in its
functional immunoglobulin light chain and heavy chain genes. |
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Term
| What is the relationship between artificial immunization and the phenomenon of clonal selection? |
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Definition
Immunization prepares your system to respond more rapidly the next
time you encounter the antigens you were inoculated with. The reason you
can mount a more rapid response the second time is that the first exposure
caused a multiplication of memory cells in the specific defense system
which recognize that antigen. This specific multiplication is called clonal
selection. |
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Term
| Based on the concept of the epitope, explain how immunization with a disables or killed pathogen can provide protection against a later exposure to the living version. |
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Definition
A given antibody or T cell receptor does not recognize an entire
bacterium or virus; it recognizes only a small portion of one antigenic
molecule found in the pathogen: an epitope. This epitope would look the
same to the antibody or T cell receptor whether it was attached to a fully
functional pathogen or a disabled one |
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Term
| Why doesn't your immune system attack your own healthy cells? Why don't your macrophages attack your own healthy cells? |
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Definition
During the process of maturation of the cells of the immune system they
are tested against your body’s own antigens, in particular the MHC. Cells
responding too vigorously to your own MHC antigens have their
development halted.
In order for a macrophage to attack a cell, that cell must have certain
surfaces features found only on invaders or must be coated with
antibodies that bind only to invaders. |
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