15. Parasites I Flashcards
(24 cards)
What is a parasite?
An organism that lives on or in another organism (host) and benefits by deriving nutrients at the expense of the host.
What is the difference between obligate and facultative parasites?
Obligate parasites must have a host to survive, while facultative parasites can survive without a host.
Approximately what percentage of all lifeforms on Earth show parasitic lifestyles?
40%.
What are endoparasites?
Parasites that live inside the host.
What are ectoparasites?
Parasites that live on the surface of the host; examples include lice, fleas, ticks, and leeches.
What are microparasites?
Single-celled organisms, such as protozoa/protists, that require a vector for transmission between hosts.
What are macroparasites?
Multicellular organisms, such as helminths (worms), that can be several meters long.
What is a primary host?
The host where sexual reproduction occurs, often the vector.
What is a secondary host?
The host where asexual reproduction occurs, often humans or mammals.
Which parasites do parasitologists primarily focus on?
Protozoa and helminths.
What are the general characteristics of parasitic infections?
- Eukaryotic nature
- Long-duration infections
- Developmental changes
- Host preservation
- Co-evolution with host.
What is one mechanism by which parasites cause disease?
Direct physical damage, such as physical blockage or blood vessel damage.
What immune response is typically associated with microparasites?
Type 1 response.
What are key features of the Type 1 immune response?
- Pro-inflammatory
- Activated M1 macrophages
- Interleukin-12 and interferon gamma
- Natural killer cells and cytotoxic T cells
- IgG2 and IgG3 antibodies.
What is the role of IgE in parasitic infections?
It plays a major role in immunity to helminths and allergies.
Fill in the blank: Eosinophils are primarily involved in the immune response to _______.
macroparasites.
What causes high morbidity but often lower mortality in parasitic infections?
The nature of parasitic relationships with hosts.
What changes occur in the immune response during chronic parasitic infections?
Increased eosinophil and basophil counts.
True or False: Parasites generally want to kill their host.
False.
What is the significance of antigenic changes in parasites?
They occur with different life stages and can affect immune recognition.
What is the role of natural killer cells in the immune response to protozoa?
Activated by IL-12 and promote Th1 development.
What are the contents of eosinophil granules?
- Eosinophil peroxidase
- Ribonucleases and deoxyribonucleases
- Major basic protein.
What is the role of CD23 in the immune response?
Acts as a negative feedback mechanism to prevent excessive immune response.
What is the conclusion regarding parasite evolution?
Parasites have evolved sophisticated mechanisms to survive in hosts and elicit different immune responses.
