The document discusses the immune system and immunity. It defines immunity as protection against foreign microorganisms or antigens. The immune system includes both non-specific defenses that provide a general barrier against pathogens as well as specific defenses involving lymphocytes and antibodies that provide targeted protection. Lymphocytes play a key role in the specific immune response through antibody production, cytotoxic attack of infected cells, immunological memory, and regulation. The document also distinguishes between passive immunity, which is temporary, and active immunity, developed through one's own immune response.

1. IMMUNITY
AGA 207 Animal Physiology 1
Written by Dr Chikwanda
Uploaded byWaiton Sherekte

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