Neonatal immunity Flashcards
Describe the immune system of a neonate?
well developed, not 100% functional
Why is the immune system of a neonate not 100% functional?
Hasn’t seen any antigens yet = non-functional lymphocytes- complete development requires antigen stimulation
Describe foetal immune development
- Thymus develops first followed by secondary lymphoid tissues
- CMI develops at same time as Ab based immunity
- foetus does not require a functional immune system
How does lymphocyte development change at birth?
- Macrophage + neutrophil proportion increases, T + B cell proportion decreases
- Neutrophil function is reduced but cell is fully functional- key parts of complement pathway missing
Name 2 common infections that could occur during pregnancy
Neospora caninum + BVDV
Explain the differences in the effect of Neospora caninum infection on the foetus at different stages of pregnancy
- 1st trimester = foetal immune system not developed- causes absorption of mummified foetus
- 2nd trimester = foetal immune system not developed + maternal inflammation- causes abortion
- 3rd trimester = foetus immunocompetent- parasite invasion limited leading to congenital infection
What kind of immune response is neonatal immunity + where does it come from?
Always primary
- maternally derived Abs from colostrum +/or placenta
- some lymphocytes in colostrum
Describe how the transfer of immunity differs b/w species
- Placental transfer = primates (IgG only)
- 5% placental/ 95% colostral = cats + dogs
- 100% colostral = ruminants, pigs + horses
When + where is colostrum produced?
produced in mammary glands in last few wks of pregnancy
Describe the process of colostral development
active transfer of Igs from blood to mammary gland under influence of oestrogen + progesterone
Name the main colostral Ab
IgG
Describe how the components of colostrum changes as it turns to milk
Reduced Ig content + proportionally more IgA
Apart from Abs what else does colostrum consist of?
cytokines, hormones, growth factors, other immune cells
Describe + explain the process of colostrum transfer
- colostrum ingested + passes into GI tract where enzyme levels are low/ blocked = proteins can reach SI
- Newborns have specialised Fc receptor (FcRn) on intestinal epithelia
- In GI tract Igs are bound, actively pinocytosed + quickly reach lymphatics + circulation
Describe the species differences in colostrum transfer
- Horse + pig = IgG + IgM selectively absorbed to blood, IgA stays in intestine
- Ruminants = all Igs go into blood
Why does colostrum need to be given so soon?
Intestine is only permeable for short period- begins declining after 6hrs
How much colostrum do calves + foals require (minimum) within 6hrs birth?
1L
How long do newborn cows have an oesophageal groove?
20 days
What role does the oesophageal groove in calves have?
diverts colostrum + milk straight to abomasum, avoiding rumen + omasum = colostrum/ milk avoids souring in rumen + readily absorbed
What can failure of passive transfer cause + why?
causes infections- IgG prevents septicaemia, IgA prevents enteric disease
In what circumstance can failure of passive transfer occur?
- failure of production- premature lactation/ dripping
- failure of ingestion- multiple births/ damaged teats
- failure of absorption- major cause in horses
How is failure of passive transfer diagnosed?
measure serum IgG using a hydrometer/ colostrumeter
- measures specific gravity which correlates w/ protein + IgG content
How can failure of passive transfer be treated in animals <15hrs old?
administration of additional colostrum using bottle/ nasogastric tube
How can failure of passive transfer be treated in animals >15hrs old?
Use IV plasma- no oral absorption
Explain the response of neonates to vaccines
- GI lymphoid tissues respond well to ingested Ags
- passive immunisation inhibits development of immune response = non-suckled calves make Abs sooner than suckled calves
Why does passive immunity inhibit development of immune response?
maternally derived antibodies inhibit Ab production
