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?

Memory B cells Signup and view all the answers

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

Prevent the entry of bacteria and neutralize exotoxins Signup and view all the answers

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

IgG Signup and view all the answers

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

To change the class of antibody for better efficacy Signup and view all the answers

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

They reside in the gut and bone marrow Signup and view all the answers

What does hyposplenism primarily refer to?

Reduction or loss of splenic function Signup and view all the answers

Which of the following is a common cause of hyposplenism?

Congenital absence of the spleen Signup and view all the answers

What is the main goal of managing hyposplenism?

Reduce infection risk Signup and view all the answers

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

IgM Signup and view all the answers

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

Immunization with certain vaccines Signup and view all the answers

Which antibiotic course is typically recommended for individuals with asplenia?

Prophylactic antibiotics starting at birth Signup and view all the answers

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

Polio Signup and view all the answers

What is a recommended action for monitoring patients with hyposplenism?

Annual measurement of antibody titers Signup and view all the answers

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

IL-4 Signup and view all the answers

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

TLR2 Signup and view all the answers

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

Trichuris trichiura Signup and view all the answers

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

TNF and IL-1 Signup and view all the answers

What type of immune response do Th2 cells primarily mediate?

Humoral immunity Signup and view all the answers

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

Mast cells and eosinophils Signup and view all the answers

What is the role of antibodies against Streptococcus?

Opsonisation Signup and view all the answers

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

By containing proteases that kill worm pathogens Signup and view all the answers

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

Adaptive immune response Signup and view all the answers

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

TNF Signup and view all the answers

What is the role of eosinophils in helminth infections?

They release histamine to increase mucus secretion. Signup and view all the answers

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

Isotype switching towards IgE and IgG Signup and view all the answers

What is Opsonisation primarily responsible for in immune response?

Tagging pathogens for destruction Signup and view all the answers

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

Pathogen-associated molecular patterns (PAMPs) Signup and view all the answers

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

IL-4 Signup and view all the answers

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

Enhancing phagocytosis Signup and view all the answers

What causes inflammation during an immune response?

Release of secretory antigens like IL-1, TNF, and IL-8 Signup and view all the answers

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

Adaptive immunity Signup and view all the answers

What role do eosinophil granules play in fighting parasites?

They release proteins that are toxic for the parasite. Signup and view all the answers

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

Asthma. Signup and view all the answers

Which interleukin is most associated with TH2 responses?

IL-4. Signup and view all the answers

What benefit do IgE antibodies provide in terms of infections?

Help in case of a secondary infection. Signup and view all the answers

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

Asthma. Signup and view all the answers

What type of organisms are classified as extracellular infections?

Bacteria that live outside of cells Signup and view all the answers

Which immune cells are primarily involved in detecting extracellular infections?

Macrophages and dendritic cells Signup and view all the answers

How do antibodies contribute to the elimination of extracellular infections?

By activating complement and neutralizing pathogens Signup and view all the answers

What is a characteristic of hyposplenism?

Decreased removal of pathogens from the blood Signup and view all the answers

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

Both innate and adaptive immune responses are required Signup and view all the answers

What distinguishes extracellular bacteria from intracellular bacteria?

Extracellular bacteria multiply outside of host cells Signup and view all the answers

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

Humoral immunity, mostly using antibodies Signup and view all the answers

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

Helper T cells Signup and view all the answers

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

Inflammation can lead to both localized and systemic effects Signup and view all the answers

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

They initiate and regulate immune responses Signup and view all the answers

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

Antibody persistence over months to years Signup and view all the answers

Which of these infections primarily engages the adaptive immune response?

Helminths Signup and view all the answers

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

Staphylococcus aureus Signup and view all the answers

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.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

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.