Exam 2 (Lecture 16) - Fetal and Neonatal Immunity

Question 1

Describe the consequences of fetal infection and explain the factors that influence the outcome.

Answer 1

Consequences:
- Death (abort, stillborn)
- Malformation/congenital anomalies
- Successful immune response (high IgG titer)
- PI (used by BVD virus to evade ad. immunity)

Factors That Influence Outcome:
- Virulence and type of organism
- Dose of organism
- Age of fetus

Question 2

Compare and contrast how neonates of different domestic species receive antibody from their mother (primates vs. dog/cat vs. horse, cow, pig).

Answer 2

Primates:
- All passive immunity (systemic) crosses placenta

Dog/Cat:
- Approx. 10% of passive immunity crosses
placenta; the rest comes from colostrum

Horse/Cow/Pig:
- All passive immunity is via colostrum

Question 3

Explain the absorption of colostral antibody and describe the unique features of the neonate’s gut that allow the absorption of whole immunoglobulin molecules.

Answer 3

The uptake is via receptor mediated or whole macromolecules (mostly IgG) from the GI tract get into the bloodstream.

Neonate’s gut contains special epithelial cells that accommodate the uptake of large molecules (whole antibody molecules).
- There is also low proteolytic activity in the gut of
the neonate

Question 4

Explain “gut closure” – what it is, when it occurs, and how it occurs.

Answer 4

What it is:
- The specialized gut epithelium is replaced with
normal epithelial cells so macromolecules can
no longer be absorbed through the GI tract.

When it occurs:
- Approximately 24 hours after birth (influenced
by the amount of colostrum)

How it occurs:
- Specialized epithelial cells are replaced by
normal gut epithelium.

Question 5

Compare and contrast colostrum and milk, including the type of antibody, source of the antibody, and concentration of antibody.

Answer 5

Colostrum:
- Type of antibody: IgG
- Source of antibody: mother’s bloodstream
- Concentration of Ab: High

Milk:
- Type of Ab: IgA
- Source of Ab: plasma cells in mammary tissue
- Concentration of Ab: Low

Question 6

Briefly explain with words (and a drawing of each = draw a positive result) the basics of the SRID, SNAP, and immunoturbidimertirc assay (TIA) for diagnosis of FPT in foals.

Answer 6

**Drawing in notes!

SRID:
- Precipitate test
- At zone of equivalence IgG in the serum and
anti-IgG in agar form precipitate line
- Diameter of precipitate line is measured and
compared to standards

SNAP:
- Anti-equine IgG immobilized in nitrocellulose
membrane at sample spot
- Anti-equine IgG binds IgG in foal sample if
present
- Conjugate (enzyme-labeled anti-equine IgG)
is added and binds to foal IgG
- Substrate is added and if enzyme is present,
color change will occur

TIA:
- Anti-equine IgG added to blood plasma
- Immune complexes form
- Plasma become turbid (more turbid = more IgG)