2. Body
defense and
the immune
system
Body defense: Is protection against injury
Immunity: Is the protection against foreign micro-
organisms or the harmful effect of antigenic
substances (antigens)
Antigens: are molecules that can stimulate
immune response directed at the specific molecule.
Most cases antigens are components of foreign
cells or secretions from microorganisms
Non specific defense: General defense that do not
need to recognise specific antigens to be effective
protect the body against injury.
3. Foreign: Refers to cells or substances that are not self
Self: Cells or substances that are normal components of an animal’s body &
that do not normally elicit an immune response
The ability to distinguish between self and foreign is critical to the immune system
Auto-immune disorder: occurs when the immune system erroneously identifies
self tissues or antigens as foreign & mounts an inappropriate immune response
4. The immune system should also identify self cells
that have changed so that they can be harmful.
Identification and destruction of changed cells is
important in protecting against cancer
5. Immune
System
Def: Refers to all structures and cells involved in
providing immune protection
Cells of this system can be found throughout the
body in many tissues
Lymphocytes are the primary cell type involved in
an immune response and their wide distribution
throughout the body provides them ready access to
invading microorganisms
6. Lymphocytes are not a uniform group of cells but in
general
Primary response of lymphocytes are:
production of circulating antibodies (humoral
response)
Generation of lymphocytes capable of removing
the potential harmful cell (cellular response) or both
7. Inflammation: is the response of tissues to injury characterised by:
Swelling
Pain,
Heat and redness
The above are produced in response of tissues to injury
Desired outcome to injury is complete repair and restoration of tissues to
original state
8. Effects of injury produce local changes that initiate
inflammatory response
Cells attracted to the site of injury leukocytes and
macrophages also participate in inflammatory
response
9. Non specific
defenses
Include:
Epithelia that covers surfaces exposed to the
external environment confers a protective barrier
that prevent entry of injurious agents
Protective barrier enhanced by epithelial secretions
such as HCl in the stomach and non specific
antimicrobial agents in saliva e.g. lysozyme
Physical damage to the epithelial barrier may
provide entry point for harmful agents to reach
body fluids and spread
10. Non-specific
or innate
response
Damage to the epithelial barrier by microbes or
injurious agents initiate a response and
inflammation
Initial phases of the inflammation response are
immediate and similar regardless of the type and
identity of the microbe or pathogen
Referred to as non-specific or innate responses
11. Local tissue phagocytes (microphages) are among
the first cells to respond in non specific response
They engulf and destroy any foreign microbe or
substance
Neutrophils are also attracted to the cite of injury
as part of the non specific response
Cytokine: Is a term applied to all chemical
messengers (mainly proteins) that regulate cells
involved in any immune response
12. Specific or
acquired
immune
response
Def: Is the identification of the specific microbe or
agent and development of a response directed to
that specific agent
Important characteristic of acquired immunity is:
Specificity &
memory
13. The two characteristics of specificity and memory
are the basis of vaccination
Vaccination: is the deliberate induction of a
specific immune response and immunologic
memory by planned exposure to an antigen in a
manner that does not cause disease
14. Lymphocytes: are the important leukocytes that develop a specific immune
response. Their functions in this response are to:
1. Antigen recognition
2. Antibody production
3. Cytotoxic attack on infected cells
4. Immunologic memory
5. Regulation of the specific immune response
This function is not done by a single cell but subpopulations are responsible for
different aspects of the specific immune response
15. B
Lymphocyte
s
B Lymphocytes (B cells): are lymphocyte subtype
responsible for the production of antibody or the
humoral component of a specific immune response
Steps of their immune response:
1. Recognition of antigen by B cells. Antigen binds
to specific membrane receptor on B Cells and
causes them to proliferate (clonal selection)
2. Cells then differentiate into plasma cells that
produce antibodies specific to the antigen. Each
plasma cell produces only one antibody
16. 3. Other B cells develop into memory cells
These remain in the body for extended periods of
time sometimes for a lifetime
Any second infection later n life the immune system
will be ready and the immune response will be
accelerated and amplified
(For further reading: Frandson 7th
edition page 274-
275)
17. Immunoglob
ulins
Immunoglobin is a term that is given for a protein
that can bind to an antigen
Includes both antibodies (circulating
immunoglobins), &
Those found on the cell membranes of B Cells
Immunoglobins fall into five major classes based o
their chemical and functional characteristics (see
Table 16- 1 Frandson 7th
edition)
18. T Cells and
Cell
Mediated
Immunity
T Cells are a type of lymphocytes associated with
the component of an immune response known as
cell mediated immunity
It is different from humoral response involved with
antibodies that have their effects at distant sites
from their site of production in that
In Cell mediated immune response, the responding
T Cell need to be in contact with the cells bearing
the foreign antigen
19. Passive
Immunity
Def: PI is a state of temporal immunity achieved by
the transfer of immunoglobins or T Cells from an
animal to another that has not encountered the
antigen involved
Passive immunity is a temporal state because the
immunoglobins and or T Cells are degraded or
destroyed over tie
E.g. Mother to foetus transfer; mother to child
through colostrum, antidote in snake venom
treatment
20. ACTIVE
IMMUNITY
Def: Is a state of immunity to a specific antigen
achieved by the response of one’s own immune
system
Active immunity involves both humoral and cell
mediated responses
21. Further
reading
Further reading. See handout on the lymphatic
system covering:
i. Lymphatic vessels
ii. Lymph nodes
iii. Spleen
iv. Thymus
v. Tonsils
