Neonatal immunity

Question 1

What does complete immunity development require?

Answer 1

Antigen stimulation

Question 2

Neonates have a well-developed immune system when born, but not 100% functional. Why is it important to immediately control microbial invasion?

Answer 2

Mammals develop from sterile environment - born into one that isn’t sterile!
Vulnerable to infection in first few weeks of life

Question 3

Why don’t foetuses themselves require a functional immune system?

Answer 3

Develop in a sterile environment

Question 4

What lymphoid organs appear first in the foetus? What does CMI develop at the same time as?

Answer 4

Thymus
Then secondary lymphoid organs
Antibody production

Question 5

Why are intrauterine infections that are harmless to the mother serious for the foetus?

Answer 5

Foetus has tolerance to pathogen

Question 6

What is tolerance? Why is this used?

Answer 6

Lack of immune response to a specific antigen

Stops immune response to self tissues

Question 7

What viral disease has tolerance in calves after intrauterine infection?

Answer 7

BVD - bovine viral diarrhoea

Infection in utero means calf will be infected if re-challeneged

Question 8

How are maternally derived antibodies transferred to a neonate?

Answer 8

Colostrum

Placenta

Question 9

Apart from maternally derived antibodies, what other immune feature is found in colostrum?

Answer 9

Lymphocytes

Question 10

What % of the mothers immunity is transferred to offspring via placenta and colostrum? (Cats, dogs, ruminants, pigs, horses)

Answer 10

Cats and dogs - 95% colostrum, 5% placental

Pigs, ruminants horses - 100% colostral

Question 11

What transports antibodies into the mammary glands from blood? What hormones influence the movement of Abs into the mamamry gland?

Answer 11

Fc receptor - also allows neonates to absorb antibodies in SI
Oestrogen and progesterone

Question 12

What lymph node is found in the udder?

Answer 12

Supramammar lymph node

Question 13

What is the main antibody in colostrum? What is the main antibody found when colostrum changes to milk?

Answer 13

Colostrum - IgG

As changes to milk - IgA

Question 14

Where is all the IgG, most IgM and half of IgA in colostrum derived from?

Answer 14

Serum

Question 15

What is found in colostrum?

Answer 15

Antibodies
Lymphocytes
Growth factors (cytokines)
Other hormones

Question 16

Intake of colostrum is essential in the first few hours of life. Why are the antibodies not digested in the neonate GI?

Answer 16

Enzyme levels are low/blocked so they can reach the SI

Question 17

How do neonates absorb the maternally derived antibodies in colostrum?

Answer 17

Specialised Fc receptor on intestinal epithelium

Antibodies are actively pinocytosed to reach lymphatics and circulatory system

Question 18

What is the function of the oesophageal groove?

Answer 18

Divert colostrum from rumenoreticulum and omasum to abomasum
Avoids milk/colostrum souring in rumen and causing acidosis

Question 19

What volume of colostrum do calves and foals need? Within how many hours of their life?

Answer 19

1L within first 6 hours

Question 20

How does the absorption of colostrum differ in horses and pigs, compared to ruminants?

Answer 20

Ruminant - all antibodies go into blood

Horse and pig - IgG and IgM absorbed in blood, IgA stays in intestine

Question 21

Why is it essential that colostrum is absorbed within the first 6 hours (preferably) of life?

Answer 21

Intestine has Fc receptors to antibody for short period of time
Permeability starts declining after 6 hrs
Almost no Fc receptors by 24 hrs - no antibody absorption

Question 22

At what age are peak levels of circulating antibodies in the neonate?

Answer 22

12-24 hrs old

Question 23

What happens to MDA in the first few weeks of life?

Answer 23

Slowly decline

Young starts producing own antibodies

Question 24

Why are unsuckled animals prone to bacterial infections

Answer 24

Low MDA - don’t make own antibodies straight away

Question 25

What is the immunity gap? Why is this?

Answer 25

Period where neonate at risk of infection

Due to MDA becoming inadequate and puppies own antibodies still developing

Question 26

At what age is the immunity gap in puppies?

Answer 26

4-12 wks

Question 27

How can you measure colostrum quality? What do these measure?

Answer 27

Hydrometer/colostrometer

Protein and IgG content

Question 28

What are the consequences failure of passive transfer? (FPT)

Answer 28

Very serious - infections with antibody deficit
IgG prevents sepsis
IgA prevents enteric disease

Question 29

What can cause failure of passive transfer?

Answer 29

Premature lactation/dripping
Multiple births
Damaged teats
Absorption (major cause in horses)

Question 30

How can failure of passive transfer be treated?

Answer 30

Bottle or nasogastric tube of colostrum (<15 hrs old)
IV plasma (>15 hrs old - little intestinal permeability to antibodies, little Fc receptors)

Question 31

Colostrum also contains lymphocytes. Are these mainly T or B cells? How long do they survive in newborn calf intestines?

Answer 31

Mainly T cells

Up to 36 hrs

Question 32

Why aren’t T cells in colostrum rejected by neonates immune system?

Answer 32

Recognised as ‘self’

Question 33

Why do non-suckled calves make antibodies faster than suckled calves?

Answer 33

MDAs inhibit own antibody production

Passive immunisation inhibits development of immune response