B19. Foetal, newborn and maternal immunity

Question 1

Sequence of immune organ development

Answer 1

1. Thymus
2. Bone marrow, spleen, IgM
3. Secondary lymph organs, IgG

Question 2

Foetuses can also respond to atg

Answer 2

o Most important thing is the B cell selection in the primary lymphoid organs during the foetal life - not an immune response but a selection. This is to develop tolerance of self.
o Positive and negative selection can go on for a while after birth as well, so there is no sharp line to a real immune response.
o Important for some atg before birth due to foetal response - vaccination before birth!

Question 3

Types of placenta

Answer 3

• Haemochorial (primates, rodents) - IgG can cross (IgM, A, E cannot)
• Endotheliochorial (dogs, cats) - only 5-10% of IgG can cross
• Epitheliochorial (eq, pig) - cannot cross
• Syndesmochorial (ru) - cannot cross

Question 4

. Foetal, newborn and maternal immunity

Answer 4

• Foetuses do not have fully developed immune system; it is ready to react with atg, but lymphocytes are hard to activate because they do no know how to communicate with each other. Further development is needed and the phagocytic cells must learn how to function and produce cytokines.
• Complement system and phagocytosis also occur in a very low level - new borns cannot protect themselves!!
o I takes weeks or months depending on species before it can do that, it needs help to be protected —> nature invented maternal immunity.
o The initial period after birth the protection is provided by the mother by passive immunity through foetal life or colostrum.
o In some species the Igs can pass the placental barrier, and they are also found in the colostrum which also contain lymphocytes.
o Ig are different, they also come from the mother but depending on the structure of the placenta, they may or may not go through the placenta.
o Even in primates and rodents which has placental Ig, the colostrum is important due to the lymphocytes and continuation of their own immune response.

Question 5

Colostrum

Answer 5

• Contains atb for immediate protection of the young animal, and active cells (T and B cells, plasma cells) that can be absorbed during a short period of time after birth.
• The active cells are not responsible for immediate protection, but helps the young animal to develop its own functional immune response by activating the new borns immune system.
• The lymphocytes are important for production of cytokines - the cytokines from the colostrum will activate the new borns own lymphocyte receptors!
• Th are the most important ones. They produce cytokines which will bind to cell receptors in the young
• animals, and the cells will be more sensitive.
• Without the maternal cells the development of the immune system would take very long.
• The cells penetrate by loosen up the cell layer in the intestinal epithelia and push their way into the tissues.
• Changes in the gut up to 24 h, the first 6h are the best ones. The atb transferred in the colostrum are the same circulating the blood of the mother.
• Do not move the new borns to new environments! They have no atb from it since the mother has not been there.
• Significant drop of atb in the colostrum already after 24h, but the amount from the start is huge! If the young receives the colostrum for the first time at 6h it is still enough.
• The milk contains Igs as well, not only colostrum.
o Generally IgA in non ruminants. In ru it is a combination of IgA/M.
o In milk the Igs are locally produced in the mammary glands.
• In colostrum IgA is dominant in primates while IgG and IgM in the others. In colostrum the Igs mainly come from the serum of the mother.
• IgA is a typically secretory atb with protection from degradation (GI tract of the young’s are already developed and will digest other Ig)

Question 6

IgG (colostrum) and IgA (milk) difference

Answer 6

o IgA always present in digestive tract and can protect mucosa surfaces from infection by blocking the entry of atg. IgG will be present inside the tissues. Very important in GI diseases where IgG will offer some, but not very efficient protection.
o In order to give the young’s a good IgA protection the mother has to be vaccinated. Usually live vaccines are used to induce an immune response in the mother - the mucosal surfaces are connected to the mammary glands via immunological bridges —> cells activated on the mucosal layers will migrate into the mammary glands. SO! for IgA protection and bridge utilisation mucosal surfaces have to be exposed —> vaccinate on mucosal surface through lungs or gut
o For colostral atb vaccination into skin or muscles is enough.