Lecture 9 Flashcards
(24 cards)
What do parasites do
Exploit host resources without causing much damage
For the parasite to be successful what must is do
Should coexist with the host in a state of persistent infection
What can the innate immune response be eliminated by
Phagocytosis
What are the two T cell responses
- Extracellular protozoa: Th2 cytokines release that stimulate antibody production
- Th2 cytokines activated eosinophils and mast cells - Intracellular protozoa: Certain protozoa love and replicate in macrophages, they modify this usually toxic environment to survive
- Cytotoxic lymphocytes kill infected cells
- Th1 cytokines activate macrophages
What are the 2 antibody responses
- Extracellular protozoa: may be eliminated by opsonisation, complement activation and ADCC
- Intracellular protozoa: prevented from entering the host cells by neutralisation
Why do innate and adaptive immunity combine
To eliminate protozoa
- Antibody + Complement
- Activate macrophages (Th1 cells)
What mechanisms do parasitic protozoa use for immune invasion (7)
- Antigenic variation
- Antigenic drift
- Molecular drift
- Molecular mimicry
- Intracellular localisation
- Sequestration in immune privileged sites
- Regulation of host functions
Can parasites hide from the immune system
Yes
What is the problem with immune responses against parasites (3)
- Can be detrimental to the host causing immunopathology
- Hypersensitivity reactions
- Autoimmunity
Where can hemlinth larvae be found
Various tissues
What is the central player in helminths immune response 2
Type 2 immunity is the CD4+T helper 2 (Th2) cell which produces a broad range of cytokines
What does the helminths immune response 2 induce
IgE and certain IgG subclass/isotypes
What are involved in the immune response to helminths
Mast cells and eosinophils
How can mast cells degranulate
Binding of helminth Ag to immunoglobulin E bound to the surface of mast cells
What do mast cells release following activation
Histamine, heparin, proteases, secrete cytokines IL-4 and IL-5
What do mast cells bound to IgE trigger
Degranulation, vasoactive molecules stimulated smooth muscle contraction, increased vascular permeability, increased epithelial cell turnover, worm expulsion
What role do eosinophils pay in helminth infections (3)
- Products can damage helminth cuticle
- Eosinophil cationic protein and Eosinophil derived neurotoxin are ribronucleases, toxic for helminths
- Eosinophils + Ig = ADCC
What can mediate explosion of intestinal nematode parasites
Mast-cell-independent and mast-cell-dependent
What do IL-4 and IL-3 stimulate in term of intestinal nematode parasites
Goblet cell proliferation and mucin secretion, and physiological changes in the gut epithelium and muscle that lead to expulsion
What is a mechanism of expulsion of intestinal nematode parasites
Mast cell growth and degranulation, increasing intestinal permeability, smooth muscle contractions and net fluid secretion
What type of response is key to expelling parasites and regulating immune response
Type 2 immune response
What does the type 2 immune response contribute to
Rapid tissue repair and this sometimes leads to fibrosis-related pathology
What changes over the time of helminth infections
T cell dynamics
What may a host develop
Inflammation and hypersensitivity
