medical bacteriology - powepoint 4

Questions and Answers

What is the primary function of dendritic cells in the immune system?

Initiate adaptive immune responses (correct)

Regulate inflammation through cytokines

Produce antibodies against pathogens

Directly kill virus-infected cells

Which of the following is NOT a characteristic of NK cells?

They can recognize tumor cells

They produce granzyme and perforin

They are primarily derived from bone marrow

They exclusively use antibody-mediated response (correct)

What type of proteins do cytokines primarily function as?

Hormones of the immune system (correct)

Antimicrobial peptides

Cell adhesion factors

Antigen-presenting molecules

Which component do macrophages NOT use for their immune response?

Patrolling leukocytes Signup and view all the answers

What is the primary role of chemokines in the immune system?

Direct chemotaxis to recruit immune cells Signup and view all the answers

What is the nature of the substances in the phagosome that immobilize bacteria?

Defensins and lactoferricin Signup and view all the answers

What major response do macrophages elicit upon attaching to the Fc portion of an antibody?

Activation of the complement system Signup and view all the answers

Which of the following cytokines is classified as a signaler?

TNF Signup and view all the answers

Which of the following statements about phagocytic cells is true?

They are involved in the direct engulfment of pathogens. Signup and view all the answers

What role do leukotrienes play in inflammatory responses?

Encourage monocyte recruitment from the blood Signup and view all the answers

Which mechanism of the complement system is primarily responsible for directly lysing pathogens?

Cytolysis Signup and view all the answers

What is the primary action of CD4 T helper cells in the immune response?

Activate B cells for antibody production Signup and view all the answers

Which type of interferon is produced by T lymphocytes and plays a role in cell differentiation and viral defense?

Gamma Signup and view all the answers

Which T cell subset is primarily involved in recruiting neutrophils during an immune response?

Th17 cells Signup and view all the answers

What is the role of anaphylatoxins like C5a and C3a in the immune response?

Induce vasodilation and increase vascular permeability Signup and view all the answers

Which of the following accurately describes the function of CD8 T cells?

Destroy infected cells presenting foreign peptides Signup and view all the answers

Which complement pathway involves antibody-antigen complexes and is referred to as the classical pathway?

Classical Pathway Signup and view all the answers

Which group of interferons is primarily produced by leukocytes?

Alpha interferon Signup and view all the answers

What is the function of co-stimulatory receptors in T cell activation?

To ensure the specificity of the T cell response Signup and view all the answers

Which mechanism does the complement system utilize to promote opsonization?

Coating pathogens with complement fragments Signup and view all the answers

Which cells are classified as antigen presenting cells (APCs)?

B-lymphocytes, Dendritic cells, Macrophages Signup and view all the answers

What role do Toll-like receptors (TLRs) play in the immune system?

They initiate the innate immune response by recognizing molecular patterns. Signup and view all the answers

What is the primary function of opsonins in the immune response?

To coat the surface of bacteria enhancing phagocytosis. Signup and view all the answers

Which types of receptors are classified as RIG-I-like receptors (RLRs)?

MDA-5 and RIG-I Signup and view all the answers

What is the role of pathogen-associated molecular patterns (PAMPs) in the immune system?

They activate innate immune responses by identifying conserved nonself molecules. Signup and view all the answers

What is the main function of the complement system in the immune response?

To facilitate the process of lysis of infectious organisms and opsonization. Signup and view all the answers

How do NOD-like receptors (NLRs) detect pathogens?

By sensing pathogen-associated molecular patterns within the cell. Signup and view all the answers

What is the function of MDA-5 in the immune response?

To detect viral infections as a RIG-I-like receptor. Signup and view all the answers

Which of the following is NOT a component of the innate immune response?

Antibodies Signup and view all the answers

What type of proteins are considered opsonins?

Antibodies and complement proteins that facilitate phagocytosis. Signup and view all the answers

What is the role of the co-stimulatory signal in cellular responses?

To enhance the regulation and structural stability of immune responses Signup and view all the answers

Which statement correctly describes the B cell activation process?

B cells differentiate into plasma cells and memory cells upon activation by T cells and cytokines Signup and view all the answers

What are the distinct features of heavy chains in immunoglobulins?

Heavy chains determine the class of the antibody and differ among IgG, IgM, IgA, IgD, and IgE Signup and view all the answers

In Type I hypersensitivity reactions, what triggers the degranulation of mast cells?

Binding of IgE to the offending allergen after initial exposure Signup and view all the answers

What is a characteristic feature of Type III hypersensitivity reactions?

Formation of antigen-antibody complexes that damage tissues Signup and view all the answers

Which statement best describes the role of T lymphocytes in Type IV hypersensitivity reactions?

They release cytokines upon re-exposure to the sensitizing antigen, causing inflammation Signup and view all the answers

What is the function of antibodies in the immune response?

Antibodies enhance phagocytosis, neutralize toxins and viruses, and mediate other immune responses Signup and view all the answers

How does the immune system respond during opportunistic infections in AIDS?

Both the innate and adaptive responses are compromised, allowing opportunistic pathogens to thrive Signup and view all the answers

What is the mechanism of action by which IgE antibodies induce allergic responses?

Cross-linking of IgE on mast cells causes degranulation and release of inflammatory mediators Signup and view all the answers

Study Notes

Innate Immunity Overview

Dendritic cells (DCs) serve as sentinels, initiating adaptive immune responses.
DCs originate from bone marrow and are the most potent antigen-presenting cells.
Natural Killer (NK) cells are lymphocytes that target virus-infected and tumor cells using granzyme and perforin.
NK cells utilize specific receptors for recognizing bacteria and activating antibody-dependent cellular cytotoxicity (ADCC), and are major producers of gamma interferon, an antiviral cytokine.

Phagocytic Cells and Their Functions

Phagocytic cells include monocytes, macrophages, polymorphonuclear cells (PMNs), and dendritic cells.
Toxins produced by phagocytes, such as defensins and lactoferricin, assist in immobilizing and killing bacteria.
Macrophages can enhance immune response by attaching to the Fc portion of antibodies and activating complement proteins.

Cytokines Role in Immunity

Cytokines are immune system hormones like interferon and interleukins that regulate inflammation and affect various immune cells.
Two main groups of cytokines: Signalers (like TNF and IL-1) and chemokines (which direct cell movement).
Cytokines are secreted by macrophages alongside prostaglandins and leukotrienes, leading to vasodilation and increased permeability.

Microbial Sensors

Toll-like receptors (TLRs) recognize pathogen molecular patterns to trigger innate immune responses.
NOD-like receptors (NLRs) are intracellular sensors detecting pathogen-associated molecular patterns (PAMPs).
RIG-I-like receptors (RLRs) identify viral infections within cells.

Antigen Presenting Cells (APCs)

Dendritic cells, macrophages, and B-lymphocytes phagocytose pathogens and present epitopes to naive lymphocytes.
This interaction is essential for the migration and killing of microbes by immune cells.

Opsonization and Complement System

Opsonization enhances phagocytosis through antibodies, such as IgG and C3b, that coat pathogens.
The complement system consists of over 30 serum proteins involved in pathogen lysis, inflammation, and opsonization.
There are three complement pathways: classical, alternative, and lectin—each culminating in the formation of the membrane attack complex (MAC).

Interferons and Their Functions

Interferons (IFNs) are produced by NK and T cells to combat viral infections and influence cell growth.
Classified into alpha, beta, and gamma groups, IFNs inhibit viral replication and activate immune responses.

Adaptive Immunity Overview

Adaptive immunity involves cellular responses from T and B lymphocytes, leading to plasma cell proliferation and antibody production.
Helper T (CD4) cells can differentiate into various subtypes (Th1, Th2, Th17, Treg) with specific immune functions.

T Cells and Their Functions

CD4 T cells facilitate the activation of other immune cells and promote antibody production through cytokine release.
CD8 T cells function as cytotoxic T cells targeting infected cells recognized by MHC-I presentation.

Antigen Recognition and Activation

T cell receptors (TCRs) ensure specificity by recognizing small antigen peptides presented by MHC molecules.
Co-stimulatory signals are crucial for T cell activation, providing necessary regulatory support.

Antibody Production and Functions

Activation of B cells leads to clonal expansion and differentiation into antibody-secreting plasma cells and memory cells.
Antibodies enhance phagocytosis, neutralize toxins, and mediate complement lysis.

Hypersensitivity Reactions

Type I hypersensitivity involves IgE-mediated degranulation upon re-exposure to allergens, leading to histamine release.
Type II hypersensitivity results in antibody-mediated cytotoxicity and tissue damage (e.g., autoimmune conditions).
Type III hypersensitivity is characterized by immune complex deposition and subsequent inflammation.
Type IV hypersensitivity involves T cell-mediated responses with cytokine release causing delayed inflammatory reactions.

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Description

Explore the fascinating world of innate and adaptive immunity with this quiz. Learn about key players like dendritic cells and their roles in initiating immune responses. Test your knowledge and enhance your understanding of the immune system's intricate workings.