What is the difference between a primary and secondary immunodeficiency?
Primary have a genetic, heritable basis
How can the humoral immunity be evaluated?
- CBC for lymphocytes
- Serum Ig concentrations
- Vaccination (watch response)
- Phenotyping studies (measure B-cells in blood/lymphoid tissues)
- In vitro B-lymphocyte proliferation test (function)
How can the CMI be evaluated?
- CBC for lymphocytes
- Phenotyping studies (measure T-cells in blood/lymphoid tissues)
- In vitro T-lymphocyte proliferation test
- Intradermal injection of PHA (in vivo test of function)
Which is the dominant immunoglobulin in colostrum?
IgG
When is colostrum produced?
During final weeks of pregnancy
Lasts ~24 hours after birth
How is colostrum absorbed by foals? When is it most efficiently absorbed
Specialized enterocytes bind colostral Ig
Transfer across epithelium to lymphatics and capillaries
Best absorption during first 6 hours
Is FPT a humoral or cell-mediated immunodeficiency?
Humoral
What clinical signs are associated with FPT?
D/t secondary infection (doesn’t always occur)
Umbilical infections
Bronchopneumonia
Enteritis
Bacteremia and septicemia (injected, pale, or muddy mms; tachycardia; hypoperfusion)
DIC (petechiation, hemorrhage, thrombosis)
How is sepsis diagnosed in the foal?
- Maintain high index of suspicion in any sick neonatal foal!
1. Sepsis score sheet (>11)
2. Radial immunodiffusion (RID) to measure IgG - gold standard, but pricey and time-consuming
3. ELISA-based tests - IgG >800 = adequate
- IgG <400 = complete FPT
4. SNAP test - color of blue dot indicates strength of IgG
What are the indirect indicators of passive transfer? Are they used in the foal?
Plasma TP, colostrum-derived serum GGT
Both NOT used in foals
If a foal has IgG levels 400-800 mg/dL and is clinically normal, should it be treated for FPT?
Not necessarily
How should a FPT foal <8-12 hours be treated?
PO 2L high quality colostrum (or 2-3 bottles Seramune)
SG >1.060 (colostrometer) / SG >23% (sugar refractometer)
How should a FPT foal >12-24 hours be treated?
1-2L plasma transfused IV
+/- flunixin pretreatment to reduce risk of adverse rxns
How much colostrum should the foal get?
2L of quality colostrum in first 8 hours
What screening is recommended to prevent FPT?
Screen all foals at 24-36 hours
How is FPT screened for/diagnosed in the bovine?
- Direct - FPT = IgG <1000mg/dL
- Indirect - TP (refractometer) <5.0 g/dL
(ONLY run on healthy calves with good hydration)
How much colostrum should the calf get?
100g IgG within 6 hours of birth (SG >1.050)
Dairy cows - 4L
Beef cows - 2L
What is the etiology of SCID?
Primary immunodeficiency - Arabian
Failure to produce functional B and T lymphocytes
What is the pathogenesis of SCID?
Mutation in DNA-dependent protein kinase
Lymphoid stem cells fail to differentiate
Dysfunctional B and T lymphocytes
Complete deficiency in both CMI and humoral immunity
What clinical signs are associated with SCID?
Affected foals normal for 2-3 months (until maternal Ab wanes)
Susceptible to opportunistic infections
Die within 5 months
How is SCID diagnosed?
Severe and persistent leukopenia
Low to absent levels of autologous Ig
PCR test identifies normal, heterozygous, or homozygous
How is SCID treated?
NO treatment. Grave prognosis
How is SCID prevented?
Avoid breeding carriers to one another
What is the etiology of selective IgM deficiency?
Equine specific
Humoral immunodeficiency characterized by persistently low IgM (other classes normal)
