Immunology: Immune Cell Recruitment

Questions and Answers

What does the Miasma Theory propose as the cause of contagious diseases?

Contagious diseases are caused by environmental factors such as temperature changes.

Contagious diseases are caused by bad air from rotting organic matter. (correct)

Contagious diseases are caused by organisms like bacteria and viruses.

Contagious diseases are caused by direct contact with infected individuals.

Who is credited with developing the concept known as 'Molecular Koch’s Postulates'?

Joseph Lister

Louis Pasteur

Robert Koch

Stanley Falkow (correct)

Which of the following is NOT mentioned as a reservoir for infectious diseases?

Inanimate objects

Airborne particles (correct)

Humans

Animals

What distinguishes a human carrier from symptomatic individuals in the context of infectious diseases?

Human carriers can transmit the disease even when asymptomatic. Signup and view all the answers

Which scientist's work recognized the microbial relationship in fermentation and pasteurization?

Louis Pasteur Signup and view all the answers

What is the primary role of antigen presenting cells (APCs) such as Dendritic Cells?

To capture antigens and transport them to lymph nodes Signup and view all the answers

How do naive T cells enter lymph nodes?

Via high endothelial venules Signup and view all the answers

Which type of antigen can T cell receptors recognize?

Proteins Signup and view all the answers

What do CD8 T cells recognize?

Peptides on MHC-I Signup and view all the answers

What is a requirement for naive T cells to become activated?

Activation by mature APCs Signup and view all the answers

Which cells provide help to other immune cells?

CD4 T cells Signup and view all the answers

What occurs during clonal selection in the immune response?

Only T or B cells with receptors recognizing the pathogen multiply Signup and view all the answers

What is a common way for free antigens to reach lymph nodes?

Draining in lymph fluid Signup and view all the answers

Which phrase correctly describes the expression of MHC molecules?

MHC-II molecules are expressed by professional APCs only Signup and view all the answers

How did ancient peoples connect malaria to their environment?

By associating it with 'bad air' near swamps Signup and view all the answers

Which of the following is a family of Pattern Recognition Receptors (PRRs)?

Toll-like receptors (TLRs) Signup and view all the answers

What structures do Pathogen Associated Molecular Patterns (PAMPs) commonly consist of?

Components of bacteria, fungi, or viruses Signup and view all the answers

Which statement accurately describes the expression of PRRs in different cell types?

Different cell types express certain subsets of PRRs. Signup and view all the answers

Which of the following triggers inflammation and antiviral defense mechanisms?

Engagement of PRRs Signup and view all the answers

What is the main role of DAMPs (damage associated molecular patterns)?

Indicate damage from dying cells Signup and view all the answers

Which of the following is a characteristic of PAMPs?

Common structures shared by different pathogens Signup and view all the answers

Which type of receptors recognizes germline-encoded structures?

Pattern Recognition Receptors (PRRs) Signup and view all the answers

Which of the following outcomes is NOT directly driven by the signaling cascade following PRR engagement?

Regeneration of damaged tissues Signup and view all the answers

What is the primary function of pattern recognition receptors in the immune system?

To initiate adaptive immune responses Signup and view all the answers

What role do cytokines play in the recruitment of leukocytes to sites of infection?

They promote the formation of selectins on endothelial cells. Signup and view all the answers

Which step occurs first in the recruitment process of leukocytes during an infection?

Cytokines are secreted by resident cells. Signup and view all the answers

What is the role of integrins in leukocyte recruitment?

To strengthen the interaction between leukocytes and endothelial cells. Signup and view all the answers

Where does the activation of naïve T and B cells primarily occur?

In secondary lymphoid tissues. Signup and view all the answers

What is a key characteristic of the adaptive immune system?

It relies on memory for future responses. Signup and view all the answers

Which of the following is NOT considered a secondary lymphoid tissue?

Thymus Signup and view all the answers

How do lymphatic vessels contribute to immune function?

By draining fluids and facilitating immune responses. Signup and view all the answers

What does microbial virulence indicate?

The degree or intensity of pathogenicity of a microbe. Signup and view all the answers

Which of the following is NOT a category that influences microbial virulence?

Resistance to environmental changes. Signup and view all the answers

What is one function of virulence factors?

Facilitating the colonization of host tissue. Signup and view all the answers

How does the infectious dose (ID50) contribute to successful infection?

It indicates the number of pathogens required to cause infection in 50% of hosts. Signup and view all the answers

Which of the following is a way pathogens evade host immune responses?

Encapsulation to prevent phagocytosis. Signup and view all the answers

Which factor does NOT affect host susceptibility?

Nutrient absorption efficiency. Signup and view all the answers

What role do exotoxins play in microbial virulence?

They disrupt host cell membranes, causing damage. Signup and view all the answers

Which of the following statements about virulence is false?

All pathogens have the same level of virulence. Signup and view all the answers

Study Notes

Global Recognition System

Pattern recognition receptors (PRRs) function to identify pathogens globally.
PRRs do not trigger responses to self, reflecting a healthy immune state.
Essential for initiating the adaptive immune response through interactive mechanisms.

Immune Cell Recruitment and Trafficking

Leukocytes exit the bloodstream to reach infection sites via a stepwise process.
Infection detection leads to resident cells producing cytokines and chemokines.
Cytokines promote adhesion molecules (E- and P-selectin) on endothelial cells.
Leukocytes express selectin ligands, enabling initial adhesion to endothelial cells.
Endothelial cells display chemokines on proteoglycans for leukocyte attraction.
Leukocytes transition integrins (LFA-1, VFA-4) from low to high affinity states.
This results in stronger interactions, leading to leukocyte arrest and migration through endothelial junctions.
Cells navigate toward tissue using chemokine gradients and complement fragments.

Adaptive Immune System

Takes several days to initiate a response and is characterized by specificity and diversity.
Requires activation of naïve T and B cells in secondary lymphoid tissue.
Features include clonal expansion and immunological memory, developed through "education" to avoid autoimmunity.

Lymphoid Tissue

Primary lymphoid organs include the bone marrow (B cell maturation) and thymus (T cell maturation).
Secondary lymphoid organs consist of lymph nodes, spleen, and mucosa-associated tissues.

Lymphatic System

Lymphatics are specialized vessels that facilitate fluid drainage and immune response.
Antigen-presenting cells like dendritic cells transport antigens to lymph nodes via lymphatics.
Free antigens also pool in lymph nodes and are processed by macrophages and dendritic cells.

Lymph Nodes

Comprise distinct zones for B and T cells.
Lymph enters through afferent lymphatic vessels while naïve lymphocytes migrate via high endothelial venules.

Naïve Lymphocytes

Circulate continuously through secondary lymphoid tissues.
Naïve T cells enter lymph nodes using high endothelial venules, influenced by selectin ligands and chemokines.

Antigens, Epitopes, and Peptides

Antigens elicit immune responses and include proteins, lipids, and polysaccharides.
Epitopes are specific regions on antigens recognized by lymphocyte receptors.
Cognate T and B cells respond to the same antigen, with T cell receptors primarily recognizing proteins.

B Cells vs. T Cells

B cells can detect free-floating antigens, while T cells recognize antigens presented by MHC.
CD8 T cells (cytotoxic) kill infected cells via MHC-I, whereas CD4 T cells (helper) assist other immune cells through MHC-II.

MHC and T Cell Activation

MHC-I presents intracellular peptides to CD8 T cells, activated to destroy infected cells.
MHC-II presents extracellular peptides to CD4 T cells, aiding macrophages and B cells.
Naïve T cells require signals from mature antigen-presenting cells for activation through MHC recognition and co-stimulatory signals.

Clonal Selection and Memory

Diversity of T and B cells ensures a wide range of antigen recognition.
Specific T or B cells proliferate upon pathogen encounter, leading to clonal expansion; some become memory cells for future attacks.

Microbial Disease

Recognition of various causative agents and their links in the infectious disease chain.
Understanding how disrupting any link can help control outbreaks.
The evolution from Miasma theory to Germ theory, establishing the causative role of microbes in disease.

Infectious Disease Chain Principle

Reservoirs of disease include inanimate objects, animals, and symptomatic or asymptomatic humans.
Transmission occurs through direct contact and other means, influencing disease spread.

Microbial Virulence

Virulence measures a microbe’s ability to cause disease, indicated by pathogenicity and mortality rates.
Virulence factors enable microbial survival, spread, and evasion of host defenses.

Host Susceptibility

Affected by factors such as age, socio-economic status, and immune status, impacting disease resistance.

Infectious Dose

Successful infection involves both the initial microbial dose and host susceptibility.

Pattern Recognition Receptors (PRRs)

Expressed by various cell types, essential for innate immune response.
Located on cell surfaces, endosomes, and cytoplasm, with five primary families: TLRs, CLRs, NLRs, RLRs, and CDSs.

Pathogen Associated Molecular Patterns (PAMPs)

Common structures in pathogens recognized by PRRs, distinct from healthy cells.
DAMPs indicate danger signals released from damaged cells.

PRRs in Immune Response

PRR engagement triggers a signaling cascade, promoting inflammation, cytokine production, cellular apoptosis, and adaptive immune stimulation.

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Description

This quiz covers the fundamental aspects of immune cell trafficking to sites of infection, emphasizing the roles of pattern recognition receptors and the steps involved in the recruitment of leukocytes. Understand how immune cells detect infection and communicate through cytokines and chemokines to mount an effective response.