Parasites and the Immune System

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Questions and Answers

Which immunoglobulin class is specifically produced against helminths?

  • IgE (correct)
  • IgA
  • IgM
  • IgG

What is a major consequence of the immune response mechanisms activated against helminths?

  • Destruction of host tissue through bystander damage (correct)
  • Increased antibody production against protozoa
  • Inhibition of regulatory T cells
  • Complete elimination of the helminths

What role do eosinophils play in the immune response to helminths?

  • They consume the helminths directly.
  • They trigger the production of IgA.
  • They release proteins that compromise the worms. (correct)
  • They produce antibodies specific to helminths.

According to the hygiene hypothesis, why are allergies and autoimmune diseases more common in developed countries?

<p>The regulatory T cell network is underactive. (C)</p> Signup and view all the answers

What mechanisms have helminths evolved to prevent strong immune responses?

<p>Secretion of molecules triggering immunosuppression (B)</p> Signup and view all the answers

In developing strategies for worm therapy, what aspect of helminths is most exploited?

<p>Their mechanisms of immune modulation (B)</p> Signup and view all the answers

Why are complement proteins less effective against helminths?

<p>Helminth surfaces are difficult to penetrate. (C)</p> Signup and view all the answers

Which type of parasite is specifically categorized as a macro-organism?

<p>Helminth (D)</p> Signup and view all the answers

What mechanism allows African trypanosomes to evade the host immune system?

<p>Antigenic variation (A)</p> Signup and view all the answers

Which gene expression mechanism is primarily responsible for antigenic variation in T. brucei?

<p>VSG gene expression (D)</p> Signup and view all the answers

Which of the following parasites is known for its immunosuppressive effects?

<p>T. cruzi (C)</p> Signup and view all the answers

How do helminths potentially modulate the human immune system?

<p>Through immunosuppression (C)</p> Signup and view all the answers

Which of the following is NOT a mechanism of immune evasion used by parasites?

<p>Immune memory enhancement (A)</p> Signup and view all the answers

African trypanosomiasis is primarily transmitted by which vector?

<p>Tsetse fly (C)</p> Signup and view all the answers

In parasitic infections, what role does IgE typically play?

<p>Mediates responses to helminths (A)</p> Signup and view all the answers

What is a potential therapeutic route for exploiting parasitic immune modulation?

<p>Worm therapy (D)</p> Signup and view all the answers

How do African trypanosomes evade the immune response?

<p>By changing their antigenic profile using VSG gene expression (C)</p> Signup and view all the answers

What role do IgE and eosinophils play in the immune response to parasitic helminths?

<p>They help target and attack the larger size of helminths (A)</p> Signup and view all the answers

Why cannot protein ES-62 be used therapeutically despite its anti-inflammatory properties?

<p>It triggers an immune response on its own (B)</p> Signup and view all the answers

What has been the observed effect of reduced infection rates with parasitic worms?

<p>Higher rates of development of autoimmune diseases (A)</p> Signup and view all the answers

What is the significance of VSG gene expression in African trypanosomes?

<p>It helps in overwhelming the host's antibody production (A)</p> Signup and view all the answers

What therapeutic approach is being explored to utilize the effects of protein ES-62?

<p>Use of small chemical molecules that mimic the protein's activity (C)</p> Signup and view all the answers

What is the primary immune mechanism involved in response to parasitic infections as described in the content?

<p>Bystander damage minimization by modulating responses (B)</p> Signup and view all the answers

What can be inferred about the relationship between parasitic worm infections and allergic diseases?

<p>The presence of worms reduces the immune system's response to allergens (A)</p> Signup and view all the answers

Flashcards

Antigenic variation

A mechanism where microbes change their surface antigens to avoid immune system detection.

African trypanosomes

A parasite that uses antigenic variation to evade the host's immune system.

Immune system evasion

Methods used by parasites to avoid destruction by the host's immune defense.

Intracellular location

Parasites that live inside host cells to avoid immune detection.

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Antigenic mimicry

A parasite's strategy of mimicking host proteins or molecules to hide from the immune system.

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Immunosuppression

A parasite's strategy of weakening the host's immune response to facilitate infection.

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Parasite evasion

The overall process by which parasites avoid being destroyed by the host's immune system.

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Host immune response

The body's defense against pathogens, including parasites.

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Protein ES-62

A protein secreted by a parasitic worm (Acanthocheilonema viteae) that triggers anti-inflammatory immune responses.

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Immune Response Modification

Parasites manipulating the host's immune system to evade detection or cause a desired effect.

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Anti-inflammatory Drug Development

Creating small chemical molecules that mimic the activity of proteins like ES-62 to treat inflammation and autoimmune diseases.

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Parasitic Helminths

Large parasitic worms requiring different immune responses compared to smaller microorganisms.

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IgE and Eosinophils

Immune response components used to fight parasitic worms; aim to limit bystander damage.

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Allergic Diseases Rise

Reduced parasitic worm infections might be linked to an increase in allergic diseases due to the immune system reacting wrongly to allergens.

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Immunomodulatory Drugs

Drugs that modify the immune system's activity, potentially developed from understanding worm immune responses.

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Parasitic worms and the hygiene hypothesis

Parasitic worms, like other infectious agents, affect host immune responses. The hygiene hypothesis suggests that a lack of exposure to these worms in developed countries might contribute to immune system issues like allergies and autoimmune diseases.

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Immunological responses to microbes vs. worms

Immune responses that target smaller microbes (bacteria, protozoa) are often ineffective against larger parasites (worms). Different immune mechanisms target worms.

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Regulatory T cells & worm immunity

Regulatory T cells help suppress immune responses to parasites (worms) to avoid unnecessary damage to host tissues. Worms also produce molecules to suppress the immune response.

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Hygiene hypothesis (simplified)

A lack of exposure to parasites (worms) in developed countries might lead to issues with immune regulation, possibly contributing to allergies and autoimmune diseases by altering the developing immune system.

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Immune system and allergies

The hygiene hypothesis suggests that a lack of exposure to parasitic worms during development may weaken the effectiveness of the immune system in regulating the appropriate response to environmental allergens and could lead to development of allergies.

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Worm therapy

Exploiting the mechanisms used by worms to modify the host's immunity may offer potential therapeutic benefits.

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Immune system dysfunction

The inappropriate immune response to a trigger can lead to autoimmune disease. This is a result of an altered immune system, especially in the absence of parasitic infections.

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Study Notes

Parasites and the Immune System

  • Parasites evade the mammalian immune system in various ways
  • African trypanosomes employ antigenic variation to outwit the host's antibody responses
  • IgE-mediated responses target parasitic helminths, modulating the host immune system
  • Different organisms evolved various ways to circumvent the immune system
  • Parasites may evade destruction by residing in hard-to-reach locations or expressing different surface antigens

Avoidance of Destruction by the Immune System

  • Location: Some parasites, like Plasmodium and Leishmania, reside intracellularly within host cells (liver cells, macrophages, etc.)
  • Cysts: Other parasites, such as Toxoplasma and Echinococcus, form cysts to evade destruction
  • Antigenic Mimicry: Some parasites mimic host antigens to avoid detection
  • Immunosuppression: Certain parasites, like T. cruzi, T. brucei, and filarial worms, suppress the host immune system
  • Antigenic Variation: Parasites like T. brucei, Borrelia, and Neisseria employ antigenic variation, changing surface antigens to evade detection

Antigenic Variation in African Trypanosomes

  • African trypanosomes have over 1,000 genes that code for different coat proteins
  • These coat proteins are sequentially expressed
  • This variation allows a parasite to constantly change the antigens that it expresses, thereby constantly outpacing the host immune system

Human African Trypanosomiasis

  • A disease caused by trypanosomes
  • This disease is shown in a picture of a sick man in bed being watched by a woman

T. brucei Lifecycle

  • Tsetse fly transmits parasites into a mammal's bloodstream
  • The parasite exists in two forms in the mammalian host: short and stumpy, and long and slender
  • The parasite has two life cycle stages inside the tsetse fly (procyclic and metacyclic trypomastigotes)

VSG Transcription

  • The surface glycoprotein (VSG) is vital for the parasite’s survival
  • VSGs are transcribed in only one allele (VSG gene) at a time

Successive Waves of Parasitaemia

  • A graph illustrating the fluctuating number of parasites over weeks post-infection

Parasite Sizes

  • Infectious agents vary significantly in size, from viruses to protozoa to metazoan parasites.

Parasitic Worms and the Hygiene Hypothesis

  • Immunological responses that combat "micro-organisms" are often ineffective against large "macro-organisms" like parasitic worms
  • Complement proteins and antibodies aren't effective because they can’t pass through their barriers
  • Specific immune responses against worms (e.g., IgE)
  • Eosinophils release proteins harmful to worms
  • Regulatory T cells are involved in minimizing immune damage in response to worms

Worm Therapy

  • Modifying the mechanisms used by worms to modulate host immunity is a potential therapeutic strategy
  • Protein ES-62, secreted by Acanthocheilonema viteae, triggers an anti-inflammatory response
  • Purification and injection of ES-62 reduces inflammation, potentially treating autoimmune diseases, however, the protein itself triggers an immune response

Summary of Parasites and the Immune System

  • Parasites evade the immune system
  • African trypanosomes use antigenic variation
  • Parasitic worms activate different immune responses
  • There are potential therapeutic targets by using the worms modulation methods to manipulate the immune system for better outcomes

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