Immune system of Bovines

1. IMMUNITY OF DAIRY CATTLE
Prepared by: Dr. Muhammad Umer Haider
DVM(Gold Medalist), Mphil. Pathology
Technical Service Representative
Hipra Pakistan

2. CATTLE IMMUNE SYSTEM
• Cattle, like other mammals, possess a complex immune system which helps protect them
against invasion by viruses, bacteria or other parasitic microorganisms
• The immune system produces different types of lymphocytes (white blood
cells) which are programmed to recognize specific ‘foreign’ substances, including antigens
displayed by the microorganisms which cause disease.
• The first time a cow’s immune system encounters a pathogen (disease-causing agent), it often cannot
respond quickly enough to prevent disease. However, the immune system usually succeeds
neutralizing the infection over time.
• When lymphocytes encounter a in
foreign antigen, those with specific receptors for this antigen proliferate and give rise to effector cells.

3. CONTI….
• The responses which follow are of two main types––
1- Humoral
2- Cell Mediated
• In a humoral response, the effector cells produce antibody which reacts with the
foreign antigen or microorganism and results in its elimination.
• In a cell mediated response,
the effector cells kill the cells bearing the foreign antigen, either directly or by recruiting othe
r accessory cells.
• The mammalian immune system consists of specialized lymphoid organs, plus a diffuse
network of lymphatic vessels which collect lymph and cells from tissues in almost every part
of the body, and a pool of lymphoid cells which recirculate continuously between the
lymphatic system and the bloodstream

5. IMMUNE ORGANS
Primary Organs
1) Thymus gland – T-cell system – Cell-
mediated immunity
2) Bone Marrow – B-cell system – Humoral
immunity
3) Payers Patches – B-cells- Humoral
immunity
Peripheral Lymphoid Tissue
1) Lymph nodes
2) Spleen
3) GALT

6. CONTI…
• Cells produced in the primary, lymphoid organs join the recirculating pool of
lymphocytes and populate the spleen and lymph nodes, secondary lymphoid organs
which are adapted to trapping and responding to foreign antigens.
• Each of the different lymphoid
organs has a distinct structural arrangement adapted to its specific function.

8. TYPES OF IMMUNITY
• It has two components
• Innate immunity
• Acquired or adaptive immunity

9. INNATE IMMUNITY
• This refers to the natural or inherited ability to resist disease.
• Included in this type of immunity are a number of non-specific disease response
mechanisms.It is seen before birth itself .
• This word comes from latin word ‘innatus’ which means to be born with . Birds
have well developed innate defence mechanisms. It is a slow and non-specific
immunity.
• It has three components
1) Barrier to physical attack
2) Chemical defense system
3) Cellular components

10. ACQUIRED IMMUNITY
• This refers to immunity provided by immune cells or antibodies
that are produced in response to exposure to an antigen.
• These cells and proteins circulate through the body in the blood.
• It includes targeted recognition of specific molecular features on
the surface of the pathogen.
• It is also called adaptive immunity

13. IMMUNE RESPONSE
• Developing immunity in cattle requires an effective herd
health program.
• Vaccines contain antigens of disease-causing agents, and are
used to stimulate cattle’s immune systems and create an
immune response before significant natural exposure to
disease-causing agents.
• Many factors influence the immune response to vaccinations,
including stress, vitamin and mineral balance, nutrition, and
overall health of the animal being vaccinated
• Presenting the antigens to the immune system for processing
greatly depends on the type of vaccine used and on the route
of administration.

14. CONTI..
• After an animal recovers from an infection, memory cells that have been
produced by the immune system remain for months to years.
• Memory cells are programmed to recognize specific pathogens if they
are encountered again, and facilitate a response before the pathogen
can cause disease.
• Memory cells recognize parts of a pathogen’s body called antigens.
Antigens are molecules unique to each pathogen, and memory cells use
antigens to recognize specific pathogens.
• Exposure to an antigen stimulates an immune response, which creates
memory cells for that pathogen without causing the negative effects of
an actual first infection.

16. CONT..

17. ANTIBODY –MEDIATED IMMUNE
RESPONSE
• The cattle blood has two types Red cells and White cells
• Normally lymphocytes constitute 60% of white blood cells
• Lymphocytes are produced in the bone marrow from (soft tissue
within the bones)from a cell that has the potentiality to develop into
several types of blood cell.
• This cell is known as ‘pluripotent stem cell’.

19. •

20. ANTIBODIES
• Antibodies are very small bodies of a very special protein (globulin protein) that
animals release into their circulatory system to fight invading viruses and bacteria.
• Antibodies are short lived.
• They are specific for the antigen to which they attach.
• For example, the antibody against Newcastle disease virus will attach only to the
Newcastle disease virus, not to the infectious bronchitis virus.

21. MODE OF ACTION
• Antibodies do not have the capability to kill disease organisms directly.
• Antibodies perform their function by attaching to disease organisms and
blocking their receptors and prevent them from attaching to their target cell
receptors in the chicken.
• For example: 1. A Bovine viral diarrhea virus which has its receptors covered
with antibodies will not be able to attach to and penetrate its target cells, the
cells lining the trachea.
• 2. The attached antibodies also immobilize the disease organism which
assists their destruction by macrophages.

23. TYPES OF ANTIBODIES
• In chicken 3 main type of antibodies ( Ig ) are produced .
• IgM: First antibodies produced in chicken which is actually five of the Ig’s (IgY ) joined
at the tails in a circular fashion. • The function of IgM is mainly to arrest the entry of
infectious agent.
• IgG: It consists of only one ‘y’ and hence five times smaller than IgM. It causes
clumping of the infectious agents and attach to their surfaces. This facilitates
phagocytosis.
• Ig A: The third important antibody in the chicken. • IgA is produced mainly to protect
body surfaces . This process is known as “immune elimination “. In chicken 30% to 75%
of IgA produced in the intestinal wall diffuse into the blood circulation for reaching the
liver.

25. CELL MEDIATED RESPONSE
• Lymphoid stem cells undergo a period of processing in the thymus and differentiate
into mature lymphocytes.
• The differentiated mature cells are called ‘thymus-derived lymphocytes’ , or ‘T-
lymphocytes’ , or simply as ‘T-cells’ . T stands for thymus.
• The processing and differentiation transform them into ‘cytotoxic T-cells’.
• That is they acquire the ability to kill the cells that harbour the infectious agents.

26. PURPOSE OF THE CELL-MEDIATED
IMMUNE RESPONSE
• The B-cell antibody system is meant basically to destroy the infectious agents before they reach their
targets. T-cells system is to deal with the infectious agents after they reach their target cells.
• The cell-mediated immune response is meant to deal with the infectious agents after they reach their
targets , the cells. T-cells are manufactured in the thymus ,a gland present in the neck of birds.
• While there is only one kind of antibody-producing B-cell, there are several kinds of T-cells , each
serving different functions.
• These are
• Cytotoxic T-cells-serve to kill cells infected with disease agents.
• Helper T-cells-helps in the mediation of the immune response.
• Suppressor T-cells-control cells of the immune response.

27. MODE OF ACTION
• Those cells in which the infectious agents grow within and cannot be attacked by antibodies are destroyed
by the cell-mediated immune response.
• Since viruses grow within the cells , virus-infected cells and all those cells in which bacteria or other
infectious agents grow within , are destroyed by cytotoxic T-cells to protect the body from any further
damage.
• Cytotoxic T-cells have receptors on their surface for that lock and key match. Each cell possesses about
10,000 – 20000 exactly similar receptors.
• Because all receptors are exactly the same , one T-cell will bind and kill only one type of infectious agent.

29. Role Of T-Helper Cells
• That neither the cytotoxic T-cells which kill the infected cells , nor the B-cells which produce protective
antibodies , can function without the signals received from ‘helper T-cells’.
• Helper T-cells secrete certain chemical substances (cytokines) which act as messenger molecules.
• This molecules help both B-cells and T-cells in the mediation of antibody and cell-mediated immune
responses, hence the name ‘Helper T-cell’ .
• In other words ,these cells regulate the immune responses.

30. ROLE OF MACROPHAGES
• The B –cells and T-cells do not themselves pick up the infectious agents.
• The infectious agents are first engulfed by a cell called ‘macrophage’.
• It is derived from blood cell known as ‘monocyte ‘.
• Infectious agents are broke down ,processed and then presented to T-cells and B-cells.
• Macrophages thus acts as ‘antigen-processing’or ‘antigen-presenting cell’

32. PRIMARY IMMUNE RESPONSE
• This is a response to an invader the
First time the invader infects the
body.
• No measurable immune response for
first few days.
• Next 10 – 15 days antibody
production grows steadily
• A more rapid response to an invader
the 2nd time it invades the body.
• Antibody production increases
dramatically and in a much shorter
time period.
SECONDARY IMMUNE RESPONSE
IMMUNE RESPONSE OF VACCINE