Immune Response

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  • Created on: 01-06-14 13:52
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Immune response
Primary Defence
Physical barriers:
Skin ­ The outer layer called the epidermis, which consists of a layer of cells. Most of these are
called keratinocytes. They are produced my mitosis at the base of the epidemide and migrate out to
the surface of the skin. As they migrate, they dry out and the cytoplasm is replaced with keratin. This
takes about 30days. But the time the cells reach the surface they are no longer alive. Eventually the
dead cells slough off. The keratinised layer of dead cells acts an effective barrier to pathogens.
Prevents microbial entry.
Mucous Membrane: Oxygen and nutrients must enter our blood, so the body is exposed to infection
as the gaseous substances could be harbouring microorganisms. The airways, lungs and digestive
systems are protected by mucous membranes. The epithelial layer has mucus secreting goblet cells,
in airways the mucus lines the passages and traps any pathogens that may be in the air. The epithelial
layer also has ciliated cells, which move in a coordinated fashion to waft the layer of mucus up to the
top of the trachea where it enters the oesophagus and is swallowed and passes in to the digestive
systems where most pathogens are killed by the stomach acid which has a pH of 2. This denatures
the pathogens enzymes
The eyes are protected by antibodies in the tear fluid.
The ear canal is lined by wax, which traps pathogens.
The vagina is protected by maintaining relatively acidic conditions.
Secondary Defence
Innate Immunity (Non Specific):
The process of non specific immunity.
Phagocyte is the generic name for non specific immune cells that phagocytose foreign cells and
debris. For the pathogens that are not killed by the conditions in the body, phagocytes need to kill
them before they are able to reproduce and cause any symptoms of a disease.
There are two types of phagocytic cells, neutrophils and macrophages:
The most abundant phagocyte are neutrophils. They are recognisable by their distinct multilobed
nucleus, and are manufactured in the bone marrow. They travel in the blood and are able to
squeeze out of the blood, through fenestrations in capillaries, into tissue fluid they can also be found
on epithelial surfaces such as the lungs. Neutrophils are short lived but are released in exceptionally
large numbers as a result of an infection.
The other type of phagocytic cell that is involved in the non specific response is macrophages.
Macrophages are larger cells manufactured in the bone marrow they travel around in the blood as
monocytes. They tend to settle in the body organs, particularly in the lymph nodes where they
develop into macrophages. They play a very important role in the specific responses to invading
pathogens. They are antigen presenting cells.

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Process of phagocytosis
The innate response is triggered when receptors on phagocytes bind to nonself antigens
(chemical markers on outer membrane of foreign bodies/ pathogens). Antigens are glycoprotein
found on the surface of all cells. The antigens that cover a cell are organism/individual specific, if they
belong to the organism they are considered to be self antigens, nonself antigens are identifiable by
their shape as they differ from self antigens.…read more

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Antibody/Immunoglobulins structure
Produced by lymphocytes in the immune system, and released in response to an infection. Their
shapes are complementary to a particular antigen and so are specific to one variation of antigens.
Our immune system has to manufacture one type of antibody for every antigen that is detected.
Antibodies attach to antigens and render them harmless.…read more

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Neutralisations: Antibodies attach to antigens on a pathogen that uses these antigens as a binding
site to bind with a host cell. Antibodies covering the pathogens binding site prevent the pathogen
from binding to a host cell and entering the cell. Antibodies prevent pathogens adhering to other
Agglutination: Some antibodies are larger than the Yshaped molecule they resemble many
Yshaped molecules attached together and therefore have many binding sites and can attach to
multiple pathogens at the same time.…read more

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This is the primary immune response and once the pathogens
have been dealt with the number of antibodies rapidly dropping.
Second Infection The immune system recognise the pathogen if the body is infected again, the
immune response is able to take action more quickly and are able to produce antibodies sooner and
to a higher concentration, this often is not seen externally as the body does not have time to show
symptoms of infection before the pathogen has been eradicated/dealt with.…read more

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Following the presentation of antigens is clonal selection. For T cell activation to take place they
need to undergo clonal selection, which refers to the specificity of the immune response, it would
take time for a lymphocyte with a complementary receptor to bind to an antigen being represented.
No action is done if there is not a complementary match. T cells involve dealing with virally infected
cells and any foreign cells.…read more

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Plasma cells manufacture and release antibodies
So B cells differentiate to make B memory cells which remain specific to
pathogen it was created for.
Reproduction of T Killer cells (clonal expansion done by mitosis)
T Killer ells search for infected cells to which they attach to.…read more


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