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Equine Clinical Immunology > Chapter 2: The immune system of the young horse > Flashcards

Chapter 2: The immune system of the young horse Flashcards

1
Q

What is the definition of the neonatal immune system?

A

“The neonatal immune system rapidly expands and generates appropriate immune responses to pathogens and environmental antigens.”

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2
Q

What was previously believed about neonatal immunity?

A

“Neonates were previously not considered to be immunocompetent.”

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3
Q

What have studies revealed about the immune responses of neonates?

A

“Studies of horse

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4
Q

When does the lymphoid population of the thymus develop in the equine fetus?

A

“By approximately 80 days of gestation.”

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5
Q

When are circulating lymphocytes observed in the equine fetus?

A

“By 120 days of gestation.”

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6
Q

When are secondary lymphoid tissues populated in the equine fetus?

A

“Soon after circulating lymphocytes are observed.”

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7
Q

What indicates successful B lymphopoiesis in fetal liver, bone marrow, and spleen tissues?

A

“Expression of transcripts for B cell genes like CD20

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8
Q

What evidence is there for immunoglobulin isotype switching during mid-gestation?

A

“mRNA expression of IGHM

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9
Q

What indicates the diversity of the immunoglobulin sequence content in equine fetuses?

A

“The significant increase in the variation between immunoglobulin transcripts and germline sequences between 100 days of gestation and birth.”

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10
Q

What immunoglobulin proteins are evident in fetal serum before 200 days of gestation?

A

“Both IgM and IgG proteins.”

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11
Q

What do low but detectable amounts of serum IgM and IgG at birth suggest?

A

“The fetal humoral immune system repertoire undergoes expansion and limited diversity in an antigen-independent manner during gestation.”

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12
Q

What role does colostrum play in the neonatal immune system?

A

“Colostrum provides passive transfer of antibodies

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13
Q

What soluble factors are provided by colostrum to the neonatal foal?

A

“Complement components (e.g.

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14
Q

What is the timeline for IgG absorption from colostrum?

A

“Mares start producing colostrum a couple of weeks before foaling

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15
Q

What are the primary immunoglobulin isotypes found in equine colostrum?

A

“Primarily IgG4/7

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16
Q

What is the significance of passive transfer of immunoglobulins via colostrum?

A

“It provides essential humoral protection for foals

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17
Q

What conditions may lead to failure of passive transfer (FPT) of immunoglobulins?

A

“Inadequate ingestion of colostrum

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18
Q

How is failure of passive transfer (FPT) of immunoglobulins defined?

A

“Serum IgG concentration less than 800 mg/dL by 24 hours old

19
Q

What is the incidence rate of failure of passive transfer in foals?

A

“Estimated to be between 10–18% based on a serum IgG concentration below 400 mg/dL.”

20
Q

What are common causes of septicemia in neonatal foals?

A

“Respiratory

21
Q

What are the key components of the innate immune system in neonatal foals?

A

“Phagocytes

22
Q

How does the innate immune system function in neonatal foals?

A

“Newborn foals have intrinsic phagocytic and oxidative burst activities

23
Q

What is serum amyloid A (SAA) and its role in neonatal foals?

A

“An acute phase protein that induces chemotaxis

24
Q

What are Toll-like receptors (TLRs) and their role in the neonatal immune system?

A

“TLRs recognize pathogen-associated molecular patterns (PAMPs) and initiate immune cell activation; foal neutrophils express TLR-8 and TLR-9

25
Q

How do neonatal foal neutrophils respond to Toll-like receptor (TLR) stimulation?

A

“Foal neutrophils express pro-inflammatory cytokines like IL-6 and IL-8 upon TLR-8 stimulation

26
Q

What is the adaptive immune system’s status at birth in foals?

A

“The adaptive immune system is naïve to environmental organisms but undergoes rapid expansion and maturation postnatally.”

27
Q

What changes occur in the lymphocyte population of foals during the first five months of life?

A

“Circulating B and T lymphocyte populations expand in a linear fashion

28
Q

What is the significance of lymphocyte proliferation in neonatal foals?

A

“It reflects exposure to environmental antigens and pathogens

29
Q

What are age-dependent changes observed in foal antigen-presenting cells (APCs)?

A

“Reduced MHC class II expression in foals less than three months old

30
Q

When do foals develop organized lymphoid tissue in the lungs?

A

“Bronchus-associated lymphoid tissue (BALT) is observed by 12 weeks old

31
Q

What is the role of immunoglobulin A (IgA) in the mucosal immune system of foals?

A

“IgA offers effective neutralization and opsonization of pathogens and toxins

32
Q

When do foals start producing endogenous IgA in the respiratory tract?

A

“IgA is not detected in the airway until 28 days old

33
Q

What is the dynamic phase of circulating colostrum-derived antibodies and endogenous antibodies in foals?

A

“There is a nadir in total IgG observed between the first 1–2 months of life due to the decay of colostrum-derived antibodies and rise of endogenously-produced antibodies.”

34
Q

How long does it take for foals to attain appreciable endogenous serum IgM and IgG levels?

A

“By 2–3 months of life

35
Q

What is considered adequate transfer of antibodies through colostrum at birth?

A

“A serum IgG level of at least 800 mg/dL

36
Q

When is endogenous production of immunoglobulin G4-7 (IgGb) observed in foals?

A

“IgG4-7 proteins are present in pre-suckle serum

37
Q

When does endogenous production of immunoglobulin E (IgE) occur in foals?

A

“Delayed until six months old

38
Q

What effect do passively transferred antibodies have on endogenous immunoglobulin production in foals?

A

“They may have a suppressive effect

39
Q

What cytokine production is observed in foal peripheral blood mononuclear cells (PBMCs)?

A

“Active production of TNF-alpha

40
Q

What immune responses do young foals generate to experimental infection and vaccine challenges?

A

“Antigen-specific humoral and cell-mediated immune responses

41
Q

What is the effect of vaccinating mares before foaling?

A

“Maximizes antigen-specific antibody transfer to the neonate through colostrum

42
Q

What are the challenges in neonatal vaccination?

A

“The need for immediate protection early in life with long-term memory

43
Q

What vaccination strategy has been effective against Rhodococcus equi in foals?

A

“Oral vaccination at two

44
Q

What are the implications of early exposure to environmental pathogens for neonatal foals?

A

“Exposure to pathogens before immune system priming can lead to disease

Equine Clinical Immunology (32 decks)

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