Learning Objective 1
Compare and contrast primary and secondary immunodeficiency.
- Genetic, not reversible, rare.
- Acquired, reversible, common.
Give two examples of primary immunodeficiency
Bovine Leukocyte Adhesion Deficiency (BLAD)
Severe Combined Immunodeficiency (SCID)
Both are inherited. Presentation is with surface infections early in life. Fatal.
True or False
Viral infections are one of the most important causes of secondary immunodeficiency.
Yup, that's true
True or False
Secondary immunodeficincies can be reversed if the cause is identified.
How do viruses cause immunosuppression?
Lysis of lymphoid cells
Canine distemper virus
How can bacteria cause immunosuppression?
Two mechanisms: Direct and Indirect
Indirect - the energy required to fight the bacteria causes decreased immune activity.
Direct - Leukotoxins, etc. that destroy leukocytes
Learning Objective 2
List 2 causes of secondary immunosuppression and explain how each causes immunosuppression.
- Directly kill leukocytes or require large amounts of energy to fight, depressing the immune system.
- High cortisol levels decrease leukocyte activity
- If leukocytes do not have the nutrients required to produce their proteins, etc., they will not be effective at fighting infections.
How can renal failure lead to immunosuppression?
In renal failure, large amounts of protein are lost from the glomeruli. Decreased protein means a decreased production of immunoglobulins and other important immune proteins (acute phase proteins, complement, cytokines, etc.)
How can cancer lead immunosuppression?
Most animals with cancer are immunosuppressed.
Cancer cells can secrete immunosuppressive factors like TGF beta.
List some toxic compounds that can cause immunosuppression.
Pesticides (like DDT)
Biotoxins (like aflatoxins produced by Aspergillus)
A herd of cows suddenly starts showing increased susceptibility to infectious diseases. Do you suspect a primary or secondary immunodeficiency in these animals?
Lots of animals becoming sick at the same time suggests that these animals may have acquired immunodeficiency from an external source. Things to look for include environmental toxins, malnutrition, or viral infections.
You notice that some of the horses that just ran the Kentucky Derby are showing signs of opportunistic infection. How do you suspect this happened?
High performance athletes often show signs of immunosuppression. The proposed mechanism is elevated stress and cortisol levels, leading to decreased leukocyte activity.
Why is an older animal more susceptible to infectious diseases and cancer?
As the thymus involutes, T cell function also decreases.
Explain the pathogenesis for a vet student studying for finals who comes down with an infection.
Poor nutrition from eating nothing but mac n' cheese leads to an inability of the immune system to produce the proteins it needs to function.
Stress and lack of sleep elevate cortisol levels, depressing leukocyte activity.
TAKE CARE OF YOURSELVES
Learning Objective 3
Illustrate and explain with a labeled drawing how it is often the additive effect of immunosuppressive factors that result in clinical disease and not one factor alone. Include at least two factors that decrease resistance to disease and one factor that will boost or increase resistance.
How is FIV transmitted?
Primarily through bites. Virus particles are found in saliva and blood.
Which cells does FIV infect?
CD4 T cells (similarly to HIV)
Does the FIV SNAP test detect virus particles or antibodies against the virus?
Viral levels are often too low to detect in the serum. So, look for antibodies instead.
True or False
Once a cat is infected with FIV, it will be infected for life.
Describe how the SNAP test for FIV works.
- Viral particles embedded in nitrocellulose.
- If antibody is present in the patient's serum, they will bind to the viral particles.
- Enzyme-linked FIV binds to the antibodies. The enzyme acts on the conjugate to produce a color change.
What might a positive FIV SNAP test indicate?
- Infected animal
- Vaccinated animal
- Animal that has received passive immunity (young animal that has suckled colostrum)
True or False
If kicking ass at immunology was a political accomplishment, you would be the goddam president by now.