24. Fungal and Parasitic Diseases

Question 1

Which type of host defenses play the most important role in fungal infections?

Answer 1

Delayed Type hypersensitivity = cell-mediated immunity

Question 2

Suppose a patient initially tested negative for antibody to the fungal organism, Candida albicans, but then tested positive for this antibody 3 weeks later. What do these test results indicate?

Answer 2

Patient converts from Negative to Positive = Indicates fungal (Candida albican) infection.

Question 3

What is being detected in the Cryptococcal latex agglutination test, and what are the latex beads coated with?

Answer 3

Detects Cryptococcus anitgen. Latex beads are coated with Anti-Cryptococcus

Question 4

Suppose a patient initially had a positive skin test for Candida albicans, but was skin test- negative one month later. What do these test results indicate?

Answer 4

Skin test converting from positive to negative is a poor prognostic sign = indicates immunosuppression

Question 5

For what types of protozoa do antibodies play an important defensive role?

Answer 5

Protozoa that invade the bloodstream

Question 6

For what types of protozoa does cell-mediated immunity play an important defensive role?

Answer 6

Protozoa that invade the tissues

Question 7

What are 4 ways in which protozoa can escape host immune responses?

Answer 7

1. Different developmental stages of parasites have different antigens
2. Some parasites induce suppression of the immune response.
3. Antigenic variation, or a change in parasite Ags can occur during course of infection
4. Survival of organisms can occur in macrophages

Question 8

What class of antibody and what type of white blood cell play key roles in defense against helminths?

Answer 8

IgE-mediated (Type I hypersensitivity) and Eosinophil-mediated (ADCC)

Question 9

What are 3 ways in which helminths can escape host immune responses?

Answer 9

1. Motility of worms
2. Some worms induce suppression of the immune response
3. Antigenic mimicry = worms disguise themselves with an outer coat of host Ags

Question 10

Why does the diagnosis of infectious disease require serology testing in addition to, or instead of, traditional microbiology laboratory tests?

Answer 10

Serologic testing is:

1. More rapid
2. More sensitive
3. necessary for infection where culture is difficult or not possible
4. detects past infection
5. Used to monitor the course of disease over time