Vl 10 Nematodes I

Question 1

How does the L1 larva of Trichinella spiralis change its host cell ?

Answer 1

• changes host cell (muscle cell) into a nurse cell:
• disables contractions by degrading actin and myosin
• builds up a collagen capsule and network of capillaries to protect and nourish the worm
• basophile transformation: loss of fibrils,
  architecture, intensive DNA replication

Question 2

What are the immunological mechanisms that typically lead to protective immunity
against parasitic worms?

Answer 2

TH2-response:

first contact:

• antigen is recognized by T-cells, which recruit eosinophils with IL-5 and B-cells with IL-4 and IL-13 (also recognizing antigens as foreign)
• develop specialized IgG and IgE antibodies, IgE binds to nurse cell⇒ degranulates it and attracts eosinophiles⇒ stimulate intestinal cells to widen and produce mucus and cytotoxic granula, all bind to parasite, which is flushed down

Question 3

Describe the life cycle of Ascaris lumbricoides

Answer 3

1) embryonated eggs ingested with contaminated food
2) L2 larvae hatch in small intestine
3) larva penetrate intestinal wall, enter blood stream and travel through heart and liver to lungs
4) conversion to L3 and break out into alveolus, actively migrate up the bronchi, are coughed up and swallowed again
5) grow into adults in small intestine
6) mate and produce eggs
7) unembryonated eggs passed through feces
8) in environment, eggs embryonate within 3 weeks

Question 4

What are the immunological hallmarks of helminth infections and auto-immune diseases?

Answer 4

TH2 immune response: IgE development and eosinophily (IL-4, -5 and -13)

other immune responses have problems due to overlaps

Question 5

What are the two principle drugs against nematodes and how do they act?.

Answer 5

benzimidazol - inhibits assembly of tubulin to microtubuli (broadly active against nematodes, low doses required, few side effects)

Ivermectin - paralyses worms by inhibiting ion channels (essential for neuromuscular junctions)