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P A R T 3
Drugs acting on the immune system
mild response from the immune system and somehow
tricks the T cells into allowing it to survive.
Viral invasion of cells
Viruses are genetic parasites that can survive only by
invading a host cell that provides the nourishment nec
essary for viral replication. Invasion of a cell alters the
cell membrane and the antigenic presentation of the cell
(the MHC). This change can activate cellular immunity,
or it can be so subtle that the immune system’s response
to the cell is mild or absent. In some cases, the response
activates a cellular immune reaction to normal cells
similar to the one that was invaded. This is one theory
for the development of autoimmune disease.
Autoimmune disease
Autoimmune disease
occurs when the body responds
to specific self-antigens to produce antibodies or cell-
mediated immune responses against its own cells. The
cause of autoimmune disease is not known, but theories
speculate that (1) it could be a result of response to a cell
that was invaded by a virus, leading to antibody pro
duction to similar cells; (2) production of autoantibodies
is a normal process that goes on all the time, but in a
state of immunosuppression the suppressor T cells do
not suppress autoantibody production; or (3) there is a
genetic predisposition to develop autoantibodies.
Transplant rejection
With the growing field of organ transplantation, more is
being learned about the reaction to foreign cells that are
introduced into the body. Typically, self-transplantation,
or autotransplantation, results in no immune response.
All other transplants produce an immune reaction.
Therefore, matching a donor’s HLA markers as closely
as possible to those of the recipient for histocompatibil
ity is essential. The more closely the foreign cells can be
matched, the less aggressive the immune reaction to the
donated tissue will be.
CHAPTER SUMMARY
■■
The body has several defence mechanisms in place to
protect it from injury or foreign invasion: the skin,
mucous membranes, normal flora, gastric acid, and
the inflammatory and immune responses.
■■
The inflammatory response is a general response to
any cell injury and involves activation of Hageman
factor to stimulate the kinin system and release
of histamine from injured cells to generate local
inflammatory responses.
■■
The clinical presentation of an inflammatory reaction
is heat (calour), redness (rubor), swelling (tumour)
and pain (dolour).
■■
The inflammatory response is a non-specific reaction
to any cellular injury and involves the activation
of various chemicals and neutrophil activity. The
immune response is specific to an antigen or protein
that has entered the body and involves B cells,
antibodies and T cells.
■■
Several types of T cells exist: effector or cytotoxic
T cells, helper T cells and suppressor T cells. Effector
or cytotoxic T cells immediately destroy foreign
cells. Helper T cells stimulate the immune and
inflammatory reactions. Suppressor T cells dampen
the immune and inflammatory responses to conserve
energy and prevent cellular damage.
■■
B cells are programmed to recognise specific proteins
or foreign antigens. Once in contact with that protein,
the B cell produces antibodies (immunoglobulins) that
react directly with the protein.
■■
Reaction of an antibody with the specific receptor site
on the protein activates the complement cascade of
proteins and lyses the associated protein or precipitates
an aggressive inflammatory reaction around it.
■■
Other chemicals are involved in communication
among parts of the immune system and in local
response to invasion. Any of these chemicals has the
potential to alter the immune response.
■■
The T cells, B cells and inflammatory reaction work
together to protect the body from invasion, limit the
response to that invasion and return the body to a
state of homeostasis.
■■
Problems that occur within the immune system
include the development of neoplasms, viral invasions
of cells that trigger immune responses, autoimmune
diseases and rejection of transplanted organs.
Knowing your strengths and weaknesses helps you to
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ONLINE RESOURCES
An extensive range of additional resources to enhance teaching
and learning and to facilitate understanding of this chapter may
be found online at the text’s accompanying website, located on
thePoint at
These include Watch and
Learn videos, Concepts in Action animations, journal articles,
review questions, case studies, discussion topics and quizzes.
BIBLIOGRAPHY
Abbas, A., Lichtman, A. H. & Pillai, S. (2014).
Basic Immunology:
Functions and Disorders of the Immune System
(4th edn).
Philadelphia: Elsevier Saunders.
Barrett, K. E. & Ganong, W. F. (2012).
Ganong’s Review of Medical
Physiology
(24th edn). New York: McGraw-Hill.
Doan, T. (2013).
Lippincott’s Illustrated Reviews: Immunology
(2nd edn). Philadelphia: Lippincott Williams & Wilkins.
Hall, J. (2011).
Guyton and Hall Textbook of Medical Physiology
(12th edn). Philadelphia: Saunders.
