9. Immunology

Question 1

Why is the immune system important?

Answer 1

Protects against microbial invasion

Question 2

How does the immune system work?

Answer 2

Functions through many different cell types sending and receiving messages that are delivered in the form of chemical signals. Involves hormones and cytokines which bind to specific receptors on target cells

Question 3

What is immunity?

Answer 3

Functional or protective immunity describes having sufficient biological defences against a particular pathogen, which makes the animal non-susceptible to certain diseases.

Question 4

What are specific and non-specific immunity components?

Answer 4

Specific- Act as barriers or eliminators of pathogens

Non-specific- Generation of pathogen specific immunity

Question 5

What are sickness behaviours?

Answer 5

• lethargy
• loss of appetite
• muscle and joint pain
• fever

(All components of innate immunity)

Question 6

What is the complement system?

Answer 6

An immediate response by the innate immune system. Its a response activated by both innate and acquired immune mechanisms

Question 7

What is innate immunity?

Answer 7

Non specific, defences that an animal has at birth.

Includes:

• chemicals- lysozymes in saliva, stomach acid, sweat/tears are bactericidal
• flushing mechanisms- saliva, tears, urinating, cilia
• Phagocytic WBC

Question 8

What is the inflammatory response?

Answer 8

The body releases histamine causing vasodilation resulting in the area of skin becoming reddened.

Permeability of blood capillaries is affected to enable plasma proteins and tissue fluid to leak causing swelling.

Chemical mediators are transported by tissue fluid, attracting WBCs which phagocytose dead and damaged tissue- essential for removing the initiating factor.

Question 9

What are the 2 forms of acquired immunity?

Answer 9

1. Mediated by antibodies- produced in response to a specific antigen, protects against extracellular invaders in the bloodstream (bacterium)
2. Cell-mediated immunity- protects against intracellular invaders (Viruses)

Question 10

What are antibodies?

Answer 10

Immunoglobulins- proteins produced by B lymphocytes in response to an antigen which are specific to the antigen that stimulates their production (Lock and key mechanism to form an immune complex)

Question 11

What is the acquired immune system?

Answer 11

The ability to remember prior exposure to provide a faster, more effective response to exposure- can be passive or active

Question 12

What is passive immunity?

Answer 12

An animal receiving antibodies from another animal- colostrum- the milk a newborn animal receives from the mother whom has been vaccinated.

Can only allow antibodies across during the first few hours post birth and can last 12 weeks in dogs and cats

Question 13

What types of passive immunity is there?

Answer 13

• Artificial Passive Immunity
• Antisera
• Antitoxin
• Hyperimmune sera

Question 14

What is active immunity?

Answer 14

• Natural active immunity- naturally coming into contact with antigens and the body creates antibodies to it
• Artificial active immunity- developing antibodies using a vaccine

Question 15

What are the features of immunity?

Answer 15

• specificity- specific antibodies produced for a specific antigen
• Memory
• Recognition of ‘self’- when this fails autoimmune disease results

Question 16

How do antibodies respond?

Answer 16

• primary response- the first time the body encounters an antigen it produces specific antibodies, which eventually fight off the infection. It also produces memory cells.
• Secondary response- the second time the body encounters an antigen it is recognised by the memory cells. An overwhelming production of antibodies prevents an infection establishing.

Question 17

How are antibodies produced? (Humeral response)

Answer 17

B-lymphocytes mature, antigen stimulates B cells to develop plasma and memory cells, plasma produce antibodies (only live for one day), memory cells then retain the info on how to make again

Question 18

How are antibodies produced? (cell mediated response)

Answer 18

T-lymphocytes mature in the thymus- 3 types:

• killer cells- destroy foreign cells
• helper cells- encourage b cells to change to plasma cells
• suppressor cells- suppress helper cells until the antigen is destroyed

Question 19

What are the effects of failure of passive transfer?

Answer 19

Foals are born with little or no immunity to infection from outside organisms

There is a minimal amount of immunoglobulin-M (IgM) produced in utero, but insufficient to ensure adequate external protection

Foals acquire that immunity, initially, through the mare’s colostrum, which should be high in immunoglobulins

Question 20

What is IgG?

Answer 20

maternally developed antibodies for 24 hrs post parturition (colostrum) - if this fails, mortality occurs (specifically in foals)

Question 21

What are the causes of FPT?

Answer 21

• poor lactation
• poor colostrum quality
• maternal aggression towards the foal

Question 22

What could FPT develop into?

Answer 22

• septicaemia, including septic joints or “joint ill”
• meningitis
• eye infections
• enterocolitis
• umbilical infections
• pneumonia
• death

Question 23

How can FPT be diagnosed?

Answer 23

ELISA test (snap test) - adequate passive transfer= 800mg/dl lgG, anything less is failure

Question 24

How is FPT treated?

Answer 24

colostrum administrated through nasogastric tube or per os.

plasma transfusion

Question 25

How can we prevent FPT?

Answer 25

Snap testing foals early and making sure the mare is vaccinated.