Neonatal immunity Flashcards
What does complete immunity development require?
Antigen stimulation
Neonates have a well-developed immune system when born, but not 100% functional. Why is it important to immediately control microbial invasion?
Mammals develop from sterile environment - born into one that isn’t sterile!
Vulnerable to infection in first few weeks of life
Why don’t foetuses themselves require a functional immune system?
Develop in a sterile environment
What lymphoid organs appear first in the foetus? What does CMI develop at the same time as?
Thymus
Then secondary lymphoid organs
Antibody production
Why are intrauterine infections that are harmless to the mother serious for the foetus?
Foetus has tolerance to pathogen
What is tolerance? Why is this used?
Lack of immune response to a specific antigen
Stops immune response to self tissues
What viral disease has tolerance in calves after intrauterine infection?
BVD - bovine viral diarrhoea
Infection in utero means calf will be infected if re-challeneged
How are maternally derived antibodies transferred to a neonate?
Colostrum
Placenta
Apart from maternally derived antibodies, what other immune feature is found in colostrum?
Lymphocytes
What % of the mothers immunity is transferred to offspring via placenta and colostrum? (Cats, dogs, ruminants, pigs, horses)
Cats and dogs - 95% colostrum, 5% placental
Pigs, ruminants horses - 100% colostral
What transports antibodies into the mammary glands from blood? What hormones influence the movement of Abs into the mamamry gland?
Fc receptor - also allows neonates to absorb antibodies in SI
Oestrogen and progesterone
What lymph node is found in the udder?
Supramammar lymph node
What is the main antibody in colostrum? What is the main antibody found when colostrum changes to milk?
Colostrum - IgG
As changes to milk - IgA
Where is all the IgG, most IgM and half of IgA in colostrum derived from?
Serum
What is found in colostrum?
Antibodies
Lymphocytes
Growth factors (cytokines)
Other hormones
Intake of colostrum is essential in the first few hours of life. Why are the antibodies not digested in the neonate GI?
Enzyme levels are low/blocked so they can reach the SI
How do neonates absorb the maternally derived antibodies in colostrum?
Specialised Fc receptor on intestinal epithelium
Antibodies are actively pinocytosed to reach lymphatics and circulatory system
What is the function of the oesophageal groove?
Divert colostrum from rumenoreticulum and omasum to abomasum
Avoids milk/colostrum souring in rumen and causing acidosis
What volume of colostrum do calves and foals need? Within how many hours of their life?
1L within first 6 hours
How does the absorption of colostrum differ in horses and pigs, compared to ruminants?
Ruminant - all antibodies go into blood
Horse and pig - IgG and IgM absorbed in blood, IgA stays in intestine
Why is it essential that colostrum is absorbed within the first 6 hours (preferably) of life?
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
At what age are peak levels of circulating antibodies in the neonate?
12-24 hrs old
What happens to MDA in the first few weeks of life?
Slowly decline
Young starts producing own antibodies
Why are unsuckled animals prone to bacterial infections
Low MDA - don’t make own antibodies straight away
What is the immunity gap? Why is this?
Period where neonate at risk of infection
Due to MDA becoming inadequate and puppies own antibodies still developing
At what age is the immunity gap in puppies?
4-12 wks
How can you measure colostrum quality? What do these measure?
Hydrometer/colostrometer
Protein and IgG content
What are the consequences failure of passive transfer? (FPT)
Very serious - infections with antibody deficit
IgG prevents sepsis
IgA prevents enteric disease
What can cause failure of passive transfer?
Premature lactation/dripping
Multiple births
Damaged teats
Absorption (major cause in horses)
How can failure of passive transfer be treated?
Bottle or nasogastric tube of colostrum (<15 hrs old) IV plasma (>15 hrs old - little intestinal permeability to antibodies, little Fc receptors)
Colostrum also contains lymphocytes. Are these mainly T or B cells? How long do they survive in newborn calf intestines?
Mainly T cells
Up to 36 hrs
Why aren’t T cells in colostrum rejected by neonates immune system?
Recognised as ‘self’
Why do non-suckled calves make antibodies faster than suckled calves?
MDAs inhibit own antibody production
Passive immunisation inhibits development of immune response
