2F - Helminths

Question 1

what are helmithis

Answer 1

parasitic worms; cause immunosuppression of both the innate and adaptive immune system

Question 2

helminths and hosts co-evole which leads to

Answer 2

◦ Often cause asymptomatic or subclinical chronic infection
◦ Often large numbers of animals infected with only small to moderate numbers of parasites
◦ Battle between the host immune response and the immune evasion of the parasite
◦ Helper 2 T-lymphocytes response is important
‣ Th2 cells secrete cytokines → stimulate B-Cells to develop into antibody secreting plasma cells but reduce macrophage activity → immunodulation → interactions with inflammatory and immune mechanisms involved in other infections, allergic and auto-immune diseases

Question 3

defense against helminths innate defenses

Answer 3

◦ pH of the stomach
◦ Upper GI secretions
◦ Phagocytes
◦ Complement

Question 4

Adaptive lmmune response against parasites (steps)

Answer 4

◦ Eosinophils and IgE are key players
◦ Steps
‣ Parasite gets covered in IgE (also IgA and IgG)
‣ Receptors on the eosinophil bind to the Fc portion of the antibody
‣ Then eosinophils release the toxic products of the eosinophil granules
◦ Also toxic to surrounding tissues

Question 5

Antibodies directed against worm enzymes function to

Answer 5

block penetration of the intestinal mucosa and feeding of the worm

Question 6

Mechanical response mediated by the adaptive immune system

Answer 6

◦ Intestinal anaphylaxis
‣ Ig E mediated mast cell degranulation → stimulation of fluid, electrolyte and mucus secretion, smooth muscle, contractility, increased vascular and epithelial permeability and recruitment of immune cells such as eosinophils and mast cells
‣ Elimination of the larvae and expulsion of the adult

Question 7

creation of a granuloma

Answer 7

Inflammatory cells such as eosinophils, macrophages and lymphocytes accumulation
◦ Sometimes this granuloma surrounds the parasite and stops it migrating any further

Question 8

Mucosal hyperplasia

Answer 8

caused by IgE mediated hypersensitivity results in a thickening of the intestinal wall which makes it difficult to absorb nutrients
◦ → malabsorption diarrhea

Question 9

how to parasties evade the immune system

Answer 9

◦ They produce enzymes that
‣ destroy antibodies
‣ deactivate eotaxin (the special chemokine that attracts eosinophils produced by the immune cell)
◦ They
‣ destroy antigen presenting cells,
‣ depress lymphocyte stimulation
‣ induce eosinophil apoptosis (programmed cell death)
◦ They hide by acquiring and covering themselves in host molecules like serum albumins and IgM

Question 10

how can the stages affect how the parasite avoids the host defense

Answer 10

◦ The parasite goes through different stages within the same host- Stage specific antigens
‣ Change in morphology within hosts delays immune response
‣ So much antigen is released that this dilutes or diverts host response