Immunology Year 1: Extracellular Infections
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Questions and Answers

What type of immune response is primarily generated by protein antigens associated with Streptococcus pyogenes?

  • No memory cells generated
  • Isotype switching leading to IgG and IgA production (correct)
  • Production of IgM only
  • Minimal isotype switching with IgM prevalence

What is a characteristic of the antibody production to non-protein toxins?

  • Presence of memory B cells
  • Mainly IgM production (correct)
  • Production of high-affinity antibodies
  • Generation of long-lived plasma cells

Which cytokine is associated with Th17 responses in immunity?

  • IL-23 (correct)
  • IL-4
  • IL-6
  • IL-10

Which type of B cells are generated in response to Streptococcus pyogenes and reside in the marginal zones of secondary lymphoid organs?

<p>Memory B cells (B)</p> Signup and view all the answers

What role do neutralizing antibodies play in the immune response against Streptococcus pyogenes?

<p>Prevent the entry of bacteria and neutralize exotoxins (C)</p> Signup and view all the answers

What is the primary type of antibody produced in response to Staphylococcus aureus?

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

In the context of antibody responses, what is the importance of isotype switching?

<p>To change the class of antibody for better efficacy (D)</p> Signup and view all the answers

What is a significant feature of the plasma cells generated from a B cell response to Streptococcus pyogenes?

<p>They reside in the gut and bone marrow (B)</p> Signup and view all the answers

What does hyposplenism primarily refer to?

<p>Reduction or loss of splenic function (B)</p> Signup and view all the answers

Which of the following is a common cause of hyposplenism?

<p>Congenital absence of the spleen (A)</p> Signup and view all the answers

What is the main goal of managing hyposplenism?

<p>Reduce infection risk (D)</p> Signup and view all the answers

Which type of antibody is produced by short-lived plasma cells that are affected by hyposplenism?

<p>IgM (B)</p> Signup and view all the answers

What is recommended before undergoing surgical splenectomy for those with hyposplenism?

<p>Immunization with certain vaccines (C)</p> Signup and view all the answers

Which antibiotic course is typically recommended for individuals with asplenia?

<p>Prophylactic antibiotics starting at birth (B)</p> Signup and view all the answers

Which of the following vaccines is NOT listed as recommended for individuals with hyposplenism?

<p>Polio (B)</p> Signup and view all the answers

What is a recommended action for monitoring patients with hyposplenism?

<p>Annual measurement of antibody titers (C)</p> Signup and view all the answers

What is the primary cytokine that instructs T cell differentiation into Th2 cells?

<p>IL-4 (A)</p> Signup and view all the answers

Which Toll-like receptor (TLR) is responsible for the recognition of the surface of Streptococcus?

<p>TLR2 (C)</p> Signup and view all the answers

Which of the following helminth infections is known to be associated with Ascaris lumbricoides?

<p>Trichuris trichiura (B)</p> Signup and view all the answers

What are the main cytokines produced by macrophages during an immune response?

<p>TNF and IL-1 (C)</p> Signup and view all the answers

What type of immune response do Th2 cells primarily mediate?

<p>Humoral immunity (A)</p> Signup and view all the answers

Which immune cells are specifically recruited by the action of IL-4 released by Th2 cells?

<p>Mast cells and eosinophils (C)</p> Signup and view all the answers

What is the role of antibodies against Streptococcus?

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

How do mast cell granules contribute to the immune response against helminths?

<p>By containing proteases that kill worm pathogens (D)</p> Signup and view all the answers

Which type of immune response do antibodies primarily support against Streptococcus?

<p>Adaptive immune response (D)</p> Signup and view all the answers

Which cytokine is known for its role in inflammation and fever induction?

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

What is the role of eosinophils in helminth infections?

<p>They release histamine to increase mucus secretion. (A)</p> Signup and view all the answers

What do changes in antibody production directed by Th2 cells include?

<p>Isotype switching towards IgE and IgG (D)</p> Signup and view all the answers

What is Opsonisation primarily responsible for in immune response?

<p>Tagging pathogens for destruction (B)</p> Signup and view all the answers

What is recognized by pattern recognition receptors (PRRs) in the immune system?

<p>Pathogen-associated molecular patterns (PAMPs) (D)</p> Signup and view all the answers

Which cytokine is typically involved in promoting the differentiation of T-helper cells?

<p>IL-4 (C)</p> Signup and view all the answers

In the context of immune responses, what is the function of complement activation?

<p>Enhancing phagocytosis (B)</p> Signup and view all the answers

What causes inflammation during an immune response?

<p>Release of secretory antigens like IL-1, TNF, and IL-8 (C)</p> Signup and view all the answers

What type of immunity involves antigen presentation in the lymph nodes?

<p>Adaptive immunity (C)</p> Signup and view all the answers

What role do eosinophil granules play in fighting parasites?

<p>They release proteins that are toxic for the parasite. (A)</p> Signup and view all the answers

What condition is associated with increased levels of IgE and mast cell activity?

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

Which interleukin is most associated with TH2 responses?

<p>IL-4. (D)</p> Signup and view all the answers

What benefit do IgE antibodies provide in terms of infections?

<p>Help in case of a secondary infection. (A)</p> Signup and view all the answers

Increased susceptibility to what condition is a common feature of TH2 associated diseases?

<p>Asthma. (B)</p> Signup and view all the answers

What type of organisms are classified as extracellular infections?

<p>Bacteria that live outside of cells (C)</p> Signup and view all the answers

Which immune cells are primarily involved in detecting extracellular infections?

<p>Macrophages and dendritic cells (A)</p> Signup and view all the answers

How do antibodies contribute to the elimination of extracellular infections?

<p>By activating complement and neutralizing pathogens (D)</p> Signup and view all the answers

What is a characteristic of hyposplenism?

<p>Decreased removal of pathogens from the blood (C)</p> Signup and view all the answers

Which of the following is true about the immune response to helminths?

<p>Both innate and adaptive immune responses are required (A)</p> Signup and view all the answers

What distinguishes extracellular bacteria from intracellular bacteria?

<p>Extracellular bacteria multiply outside of host cells (A)</p> Signup and view all the answers

What type of immune response is primarily involved in clearing extracellular bacteria?

<p>Humoral immunity, mostly using antibodies (C)</p> Signup and view all the answers

Which type of immune cells are activated by antigen presentation from macrophages?

<p>Helper T cells (D)</p> Signup and view all the answers

Which statement about the inflammatory response during extracellular infections is accurate?

<p>Inflammation can lead to both localized and systemic effects (A)</p> Signup and view all the answers

What is the role of cytokines in the immune response to extracellular infections?

<p>They initiate and regulate immune responses (D)</p> Signup and view all the answers

What is established by B cell memory in response to an extracellular infection?

<p>Antibody persistence over months to years (D)</p> Signup and view all the answers

Which of these infections primarily engages the adaptive immune response?

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

Which of the following is an example of an extracellular pathogen?

<p>Staphylococcus aureus (C)</p> Signup and view all the answers

Flashcards

Streptococcus pyogenes

A type of bacteria that can cause various illnesses.

Streptococcus pneumoniae

A type of bacteria that causes infections, primarily in the lungs.

Staphylococcus aureus

A common bacteria, known for causing skin infections and food poisoning.

Antibody response to streptococci

B cells produce antibodies, including IgG and IgA, for mucosal protection. Long-lived plasma cells in bone marrow and gut, and memory B cells also result.

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Isotype switching

Changing antibody types in B cells. This is important for strong mucosal protection.

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IgG and IgA antibodies

Important antibody types for mucosal protection during bacterial infections.

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Neutralizing antibodies

Antibodies that block harmful bacteria and toxins. Prevents them from entering.

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Memory B cells

B cells that remember prior exposure to a pathogen. They rapidly respond if re-encountered.

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Extracellular Infection

Infections caused by pathogens that live and multiply outside host cells.

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Innate Immunity

The body's first and rapid response to infection, non-specific to the pathogen.

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Adaptive Immunity

The more targeted response to infection; specific to the pathogen.

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Complement Activation

A part of innate immunity, proteins that enhance the immune response to pathogens.

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Phagocytosis

A process where cells engulf and destroy pathogens.

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Inflammatory Response

A reaction to tissue damage or infection causing redness, swelling etc.

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Antibodies

Proteins produced by the immune system that specifically target pathogens.

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B cell memory

Long-lasting immunity developed by memory B cells against previously encountered pathogens.

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Hyposplenism

A condition where the spleen's function is weakened or absent.

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Extracellular Bacteria

Bacteria that survive and multiply outside human cells.

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Macrophages

Immune cells that engulf and destroy pathogens.

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Dendritic cells

Immune cells that present antigens to T cells.

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T helper cells

Cells that activate other immune cells, like B cells and cytotoxic T cells.

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Cytotoxic T cells

Cells that directly kill infected cells.

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Antigen Presentation

The process of displaying pathogen fragments on the surface of immune cells.

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Immune Response

The body's response to foreign substances or pathogens.

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TLR for Streptococcus Recognition

Toll-like receptor (TLR) 2 is the main receptor involved in the recognition of Streptococcus bacteria by the immune system.

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Main Macrophage Cytokines

Tumour necrosis factor (TNF) and interleukin-1 (IL-1) are key cytokines produced by macrophages during the inflammatory response against Streptococcus.

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Antibody's Role against Strep

Antibodies against Streptococcus play multiple roles, including opsonisation, neutralisation, and complement activation, all contributing to bacterial elimination.

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Opsonisation

Opsonisation is a process where antibodies coat the Streptococcus, making it easier for phagocytes (like macrophages) to recognise and engulf the bacteria.

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Neutralisation

Neutralising antibodies bind to the surface of the Streptococcus, blocking its ability to attach to and infect host cells.

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Adaptive Immune Response

The adaptive immune response is a specific immune response against Streptococcus, involving the activation of B cells and T cells, leading to antibody production and immune memory.

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What is Hyposplenism?

A condition where the spleen's function is reduced or lost entirely.

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Functions of the Spleen

The spleen plays a vital role in filtering blood, removing old red blood cells, storing white blood cells, and producing antibodies.

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Causes of Hyposplenism

Hyposplenism can be caused by congenital absence of the spleen, surgical removal, or functional impairment due to conditions like coeliac disease or sickle cell anemia.

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Why is Hyposplenism a Problem?

Hyposplenism makes you more vulnerable to infections because the spleen is crucial for producing antibodies, particularly IgM, to fight bacteria.

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How is Hyposplenism Managed?

Management focuses on preventing infections. This involves prophylactic antibiotics, early immunizations, and regular antibody checks.

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IgM Antibodies

IgM antibodies are a type of antibody produced by short-lived plasma cells in the spleen. They are crucial for fighting off bacterial infections.

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What is the Prognosis of Hyposplenism?

With proper management, individuals with hyposplenism can live normal lives. However, regular monitoring and prompt treatment of any infections is crucial.

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What is the Importance of Early Immunizations?

Early immunizations are crucial for people with hyposplenism because they provide a protective boost to their weakened immune system, preventing infections.

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Th2-associated diseases

Conditions linked to a dominant Th2 immune response, characterized by increased IgE levels, mast cell activity, and a tendency towards allergy and asthma.

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High IgE levels

Elevated levels of immunoglobulin E (IgE), a type of antibody commonly associated with allergic reactions.

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Mast cell activity

Increased activity of mast cells, immune cells that release histamine and other inflammatory mediators, contributing to allergic reactions.

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IL-4, IL-5

Interleukins (IL) 4 and 5 are key cytokines produced by Th2 cells, promoting IgE production and mast cell activity.

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Increased susceptibility to asthma and allergy

Individuals with Th2-associated diseases are more prone to developing asthma and allergies due to the heightened immune response.

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Risk for Hyposplenic Patients

Patients with hyposplenism have an increased risk of serious infections, particularly from encapsulated bacteria. They should be advised about the risks of travel, insect bites, and bacterial infections.

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Helminth Infections

Infections caused by parasitic worms, such as Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura, Necator americanus, and Ancylostoma duodenale. These worms live in the gut and can cause various symptoms, including diarrhea, abdominal pain, and malnutrition.

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Th2 Response

A type of immune response directed towards helminth infections. It involves the activation of T helper 2 cells (Th2) which release cytokines like IL-4, IL-5, and IL-13, leading to the production of IgE and IgG antibodies.

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Eosinophils and Mast Cells

Immune cells that are important in mediating the immune response against helminth infections. They contain granules that release substances that directly kill the worms.

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Histamine Role

Histamine is released by mast cells and eosinophils. It helps to increase mucus secretion in the gut and aids in peristalsis, helping to expel the worms from the body.

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PAMPs and PRRs

PAMPs (Pathogen-Associated Molecular Patterns) are molecules found on pathogens that are recognized by the immune system. PRRs (Pattern Recognition Receptors) are receptors on immune cells that bind to PAMPs, triggering an immune response.

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TLRs (Toll-like Receptors)

A type of PRR that plays a crucial role in recognizing PAMPs and activating the innate immune response. TLRs are expressed on various immune cells, including macrophages, dendritic cells, and neutrophils.

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Innate Immune Response

The body's first line of defense against pathogens. It is non-specific and involves cells like macrophages, neutrophils, and dendritic cells, which recognize and destroy pathogens.

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Study Notes

Responses to Extracellular Infection

  • Lecture material from November 2024
  • Presented by Dr. Patrick Walsh
  • Class Year 1, Module BMF
  • Title: Responses to Extracellular Infection

Immunology Lectures Outline

  • Barrier Immunity (lecture): Physical, mechanical, and chemical barriers to infection
  • Innate Immunity (lecture): Cytokines, inflammation, complement, and antigen presentation
  • Adaptive Immunity (T cell lecture): Response to extracellular infections. Cytotoxic and helper T cells.
  • Adaptive Immunity (B cell lecture): Response to intracellular infections. B cells, antibodies.

Lecture Learning Outcomes

  • Describe the immune response to extracellular infections (using Streptococci and helminths as examples)
  • Explain how innate immune cells detect extracellular infections
  • Describe how antibodies eliminate extracellular infections
  • Explain how B cell memory is established
  • Outline conditions that cause hyposplenism
  • Describe the clinical consequences and management of hyposplenism

Immune Response Against Different Infections

  • Viruses
  • Extracellular Bacteria
  • Intracellular Bacteria
  • Fungi
  • Protozoan
  • Multicellular parasites

Extracellular vs Intracellular

  • Extracellular: Interstitial spaces, blood, lymph, Epithelial surfaces, Bacteria, Fungi, Protozoa, Helminths
  • Intracellular: Cytoplasmic, Vesicular, Viruses, Bacteria, Fungi, Protozoa

Examples of Extracellular vs Intracellular

  • Extracellular: streptococci pyogenes, staphlococcus aureus, haemophilus influenza, schistosoma mansoni
  • Intracellular: listeria monocytogenes, mycobacterium tuberculosis, viruses

Cooperation Between Innate and Adaptive Immunity

  • Macrophages and dendritic cells are the initial line of defense.
  • Existing circulating antibodies targeting outer coat proteins or lipids are important.
  • Antigen presentation to T cells activates helper T cells and cytotoxic T cells.

Overview of Immune Response to Extracellular Infections

  • Details about innate immune responses to extracellular infections.
  • All were discussed during earlier Immunity Lectures.

Innate Immunity to Extracellular Infections

  • Complement activation
  • Phagocytosis
  • Inflammatory response

Complement Activation

  • Classical pathway (activated by antibodies)
  • Alternative pathway (activated by peptidoglycans)
  • Lectin pathway (activated by bacteria with mannose on their surface)
  • Importance of MAC formation.

Phagocytosis and Inflammation

  • Phagocytosis is initiated by mannose receptors and complement receptors.
  • Killing occurs in phagolysosomes via ROS and NO.
  • Inflammatory mediators like TNF, IL-1, IL-6, IL-8, and prostaglandins are produced.

Adaptive Immunity to Extracellular Microbes (T cells)

  • T helper cells are crucial for adaptive immunity to extracellular microbes
  • Antigenic presentation leads to T cell activation
  • T helper cells aid in antibody responses

Adaptive Immunity to Extracellular Microbes (B cells)

  • B cell activation leads to antibody production
  • Isotype switching (IgG, IgA) is critical for effective protection
  • Long-lived plasma cells and memory B cells are generated

Antibody Responses

  • Neutralizing antibodies target the microbe and its exotoxins to prevent entry and promote elimination.
  • Opsonization tags the microbe for phagocytosis.
  • Complement activation and antibody activation enhance effectiveness.

Follow the Streptococcus

  • Antigen recognition - Which TLR is responsible for recognizing Streptococcus surface antigens?
  • Signaling - Which cytokines are produced by macrophages?
  • Adaptive immune response - What is the role of antibodies against Streptococcus?

Hyposplenism - Reduction/Loss of Splenic Function

  • Removal or reduced function causes increased infection susceptibility.
  • Critical role of the spleen in B cell development and antigen encounter.
  • Important to know the causes.
  • Crucial for B cell development and activation, and a site for circulating antigen encounter.
  • Hyposplenism is associated with a weakened antibody response and increased risk for infection.
  • Congenital absence, surgery, or disorders are types of hyposplenism.

Management of Hyposplenism

  • Prophylactic antibiotics (starting at birth or post-surgery)
  • Immunizations (2 weeks prior to surgery)
  • Monitoring/Measurement of antibody responses (through titers)
  • Educating patients about the risk conditions.
  • Maintaining infection prevention through medic alert bracelets

Immune Response to Other Extracellular Pathogens

  • Focus on Helminths: Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale.

Recognition and Activation of Innate Immunity

  • PAMPs (pathogen-associated molecular patterns)
  • PRRs (pattern recognition receptors), TLRs (Toll-like receptors)
  • Cytokines (IL-1/TNF/IL-8) initiate inflammation.
  • Antigen present in lymph nodes.
  • Cytokine instruction (IL-4) drives T cell differentiation.

TH2 cells and Helminth Infections

  • Key functions of TH2 cells (isotype switching to IgE and IgG, recruiting mast cells and eosinophils, mucus and antimicrobial production)
  • TH2 cells' role in fighting helminth infections

IgE & Eosinophil/Mast Cell Mediated Reactions

  • Mast cell granules contain proteases to kill the worm, and histamine increases mucus secretion.
  • Eosinophil granules are toxic to parasites.
  • Presence of IgE antibodies enhances protection from secondary infections.

TH2-associated Diseases

  • Increased susceptibility of individuals to asthma and allergies due to high levels of IgE and mast cell activity.

Streptococcus Conditions

  • The common conditions caused by Streptococcus: Pharyngitis (Strep throat), Skin Infections (Impetigo, Scarlet fever, Cellulitis) More serious conditions: Toxic shock syndrome, pneumonia, necrotizing fasciitis
  • Note various presentation methods.

Overview of Immune Response to Streptococcus

  • Extracellular microbe
  • Resident macrophages induce phagocytosis and inflammation
  • Recruitment of neutrophils
  • Antibody production by B cells
  • Antigen presentation to CD4+ T helper cells

Streptococcus pyogenes - good and bad!

  • Strep pyogenes, Strep pneumonia, Staphylococcus aureus, Candida
  • Examples of conditions related to Th17 activity, such as IBD, uveitis, psoriasis, periodontitis, arthritis, multiple sclerosis.
  • Note different methods of presenting these conditions.

B Cell Response to Streptococcus

  • Isotype switching produces IgA/IgG. This is important for mucosal protection
  • Long-lived plasma cells produce the antibodies in secondary/peripheral lymphoid tissues.
  • Memory B cells are an important aspect.
  • IgM production is mainly through the independent pathways.

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Responses to Extracellular Infection PDF 2024

Description

This quiz covers the immune response to extracellular infections, focusing on the roles of T cells and B cells, as presented in Year 1, Module BMF. You will learn how innate immune cells detect infections and how antibodies eliminate them. Example pathogens such as Streptococci and helminths will be discussed.

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