Immunology 2

Questions and Answers

What is the primary mechanism that distinguishes the initiation of the Classical Pathway from the other complement pathways?

Binding of antibodies to the pathogen’s surface (correct)

Formation of the antigen-antibody complex

Utilization of regulatory proteins for activation

Activation by polysaccharides on pathogen

How does the regulatory network function in the context of the complement system?

Facilitates constant activation of complement

Enhances the formation of antigen-antibody complexes

Minimizes tissue repair processes

Terminates complement activity to prevent tissue damage (correct)

Which step occurs after the formation of the antigen-antibody complex in the Classical Pathway?

Activation of C1 following antigen binding (correct)

Formation of C2a and C4b without C1

Direct splitting of C2 and C4

Binding of C2 and C4 to the antibody

What is the role of activated C1 in the Classical Pathway?

It activates C2 and C4 by splitting them Signup and view all the answers

Which of the following statements is true regarding the regulatory proteins in the complement pathways?

They block activation of C1 in all three pathways Signup and view all the answers

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

To produce antibodies against specific antigens Signup and view all the answers

Where do T cells undergo differentiation?

In the thymus Signup and view all the answers

Which type of lymphoid tissue is involved in gut-associated immunity?

GALT Signup and view all the answers

What are antibodies also known as?

Immunoglobulins Signup and view all the answers

What happens to mature lymphocytes after processing in primary lymphoid tissues?

They migrate to secondary lymphoid tissues Signup and view all the answers

What is the role of antibodies in adaptive immunity?

To bind to specific antigens and neutralize them Signup and view all the answers

Which statement about the lymphatic system is correct?

Lymphocytes interact with antigens in secondary lymphoid organs Signup and view all the answers

Which of the following is NOT a secondary lymphoid organ?

Thymus Signup and view all the answers

What is the primary function of CD8 T cells?

To eliminate body cells infected with intracellular organisms Signup and view all the answers

Which type of T cell is primarily associated with the regulation of immune responses?

T reg Signup and view all the answers

What feature is unique to immature B cells?

They express IgM and IgD on their surface Signup and view all the answers

What triggers apoptosis in infected cells?

Cytotoxic action of CD8 T cells Signup and view all the answers

What is the primary role of B cells in humoral immunity?

To mediate antibody production Signup and view all the answers

Which type of T cell is involved in the activation of B cells?

Th2 cells Signup and view all the answers

What characteristic distinguishes a B cell receptor (BCR)?

It responds only to specific antigens or closely related groups Signup and view all the answers

Which T cell subtype is known for their role in generating an inflammatory response?

Th1 cells Signup and view all the answers

What occurs to infected cells before any significant leakage occurs?

They undergo apoptosis and are phagocytosed Signup and view all the answers

What is a key factor contributing to the complexity of immune function?

Lymphocytes working closely with macrophages Signup and view all the answers

What is the first step in B cell activation when an antigen is present?

BCR of the B cell binds to the antigen Signup and view all the answers

Which cells are primarily responsible for producing antibodies?

Plasma cells Signup and view all the answers

What is the function of memory cells after an infection has resolved?

They continue to circulate in the host Signup and view all the answers

During the primary immune response, which immunoglobulin is produced first?

IgM Signup and view all the answers

What process involves the selection of lymphocytes that will multiply in clones?

Clonal Selection Signup and view all the answers

How many antibody molecules can a plasma cell produce per second?

2,000 Signup and view all the answers

What happens to plasma cells after the infection is over?

They die out Signup and view all the answers

What characterizes the primary immune response in terms of time taken to fully develop?

1-2 weeks Signup and view all the answers

What is the main role of BCR in B cell function?

To bind to antigens Signup and view all the answers

Which cells are formed after B cells undergo clonal selection?

Both plasma and memory cells Signup and view all the answers

What is the primary function of antibodies in the process of opsonization?

To coat the pathogen, enhancing its phagocytosis Signup and view all the answers

How do antibodies neutralize toxins?

By blocking their active sites Signup and view all the answers

What is an effect of antibody-dependent cell-mediated cytotoxicity (ADCC)?

Binding of antibodies to target cells leading to their destruction Signup and view all the answers

Which pathway enhances phagocytosis through opsonization?

Classical Pathway Signup and view all the answers

What role do eosinophils play in the immune response?

Binding to antibodies via Fc region receptors Signup and view all the answers

What is the result of the antibodies coating the surface of a pathogen?

It promotes the pathogen's susceptibility to phagocytosis Signup and view all the answers

Which of the following processes can eliminate large parasites?

Antibody-dependent cell-mediated cytotoxicity Signup and view all the answers

Which statement describes the mechanism of the classical pathway in immunity?

It enhances opsonization through antibody binding Signup and view all the answers

What occurs when antibodies coat microorganisms?

They block the adhesion of bacteria and viruses to mucosa Signup and view all the answers

What is the primary location where B cells develop in adults?

Bone marrow Signup and view all the answers

What happens to B cells after they mature?

They migrate to lymphoid organs. Signup and view all the answers

Which process involves B cells dividing into many clones upon encountering an antigen?

Clonal selection Signup and view all the answers

What type of cells actively secrete antibodies?

Plasma cells Signup and view all the answers

What is the primary function of immunogens in the immune system?

To elicit immune responses Signup and view all the answers

What role do T cells play in the immune response?

Cell-mediated immunity Signup and view all the answers

Which component is NOT considered a key player in adaptive immunity?

Viruses Signup and view all the answers

What is the term for the production of antibodies by activated B cells?

Humoral immunity Signup and view all the answers

What type of immunity is primarily associated with the function of antibodies?

Humoral immunity Signup and view all the answers

What distinguishes adaptive immunity from innate immunity?

It can remember specific pathogens for faster response upon re-exposure Signup and view all the answers

What role do antibodies play in the immune response?

They bind to pathogens to neutralize or mark them for destruction Signup and view all the answers

Which lymphoid organs are crucial for B cell activation and response?

Lymph nodes and spleen Signup and view all the answers

Which of the following best describes the response of acquired immunity?

Delayed but highly specific Signup and view all the answers

What initiates the clonal selection process in B cells?

Encountering a foreign antigen Signup and view all the answers

What do activated B cells primarily differentiate into?

Plasma cells Signup and view all the answers

What is the primary significance of determining blood types in the context of adaptive immunity?

To facilitate organ matching for transplants Signup and view all the answers

How do antigens interact with antibodies in the immune system?

Antibodies bind to specific sites on antigens called epitopes Signup and view all the answers

What is the function of the complement system in adaptive immunity?

Enhancing the ability of antibodies and phagocytes to clear pathogens Signup and view all the answers

What type of disorders is associated with deficiencies in C1, C2, or C4 complement molecules?

Collagen vascular disorders Signup and view all the answers

Which complement deficiency is particularly associated with increased susceptibility to infections?

C3, C2 Signup and view all the answers

What infectious diseases are associated with deficiencies in C5 to C9 complement components?

Neisseria meningitidis and N. gonorrhoeae Signup and view all the answers

Which cells are predominantly responsible for expressing Class II molecules?

Macrophages and Dendritic cells Signup and view all the answers

Which complements are encoded by HLA-D region's genes?

HLA-DP, HLA-DQ, HLA-DR Signup and view all the answers

Which class of molecules do CD8 T-cells primarily interact with?

Class I molecules Signup and view all the answers

What is a likely consequence of complement deficiencies?

Increased susceptibility to various infections Signup and view all the answers

Which type of cell does NOT express Class I molecules?

Muscle cells Signup and view all the answers

What specific role do Class III molecules play in the immune system?

They encode complement proteins and cytokines. Signup and view all the answers

What is the primary role of Helper T Cells in cell-mediated immunity?

Activate macrophages and assist in B-cell processes Signup and view all the answers

Which of the following statements is true regarding cytotoxic T cells?

They destroy infected host cells and foreign cells. Signup and view all the answers

What must occur for T-cells to recognize an antigen?

The antigen must be presented by MHC on an antigen-presenting cell. Signup and view all the answers

Which statement accurately describes the Major Histocompatibility Complex (MHC)?

It enables T cells to distinguish self from non-self. Signup and view all the answers

What distinguishes adaptive immunity from innate immunity in regards to cellular components involved?

Adaptive immunity primarily involves T-lymphocytes and antigen processing. Signup and view all the answers

What is the role of MHC Class I proteins in antigen presentation?

They present antigens to T cells for recognition. Signup and view all the answers

Which immunoglobulin is predominantly present on the surface of immature B cells?

IgM Signup and view all the answers

What triggers the activation of B cells?

Binding of specific antigens to B-cell receptors. Signup and view all the answers

What is the outcome of the interaction between B cells and T cells?

Production of antibodies by activated B cells. Signup and view all the answers

How does an antigen interact with B cells?

By fitting into a specific BCR, triggering a response. Signup and view all the answers

What initiates the process of antigen presentation by an antigen-presenting cell (APC)?

Capture and processing of exogenous antigens. Signup and view all the answers

Which statement accurately describes how antigens are recognized by T cells?

Antigens must be attached to MHC molecules of an APC. Signup and view all the answers

What is the primary function of the groove in MHC molecules?

To hold and present antigen fragments. Signup and view all the answers

What is the main characteristic of B-cell receptors (BCRs)?

They can bind to a specific antigen or a related group. Signup and view all the answers

What is the consequence of a B cell successfully binding to an antigen?

Clonal expansion and differentiation. Signup and view all the answers

Study Notes

Lymphocytes Overview

Two primary types of lymphocytes: B cells and T cells.
B cells differentiate and mature in the bone marrow; T cells do so in the thymus.
Mature lymphocytes migrate to secondary lymphoid organs for antigen interaction.

Antibodies

Antibodies, or immunoglobulins, are produced in response to specific epitopes on pathogens.
They help in the inactivation or destruction of infectious agents.
Antibodies can be found in blood serum, body fluids, and tissues, and are highly specific.

Humoral Immunity

Characterized by antibody-mediated responses primarily involving B cells.
Immature B cells express IgM and IgD on their surface as receptors.

B Cell Function

B cell receptors (BCR) specifically respond to individual antigens.
Activated B cells can proliferate into plasma cells and memory cells; the latter ensures long-term immunity.
Plasma cells can produce up to 2,000 antibody molecules per second.

Antibody Actions

Antibodies function through various mechanisms, including neutralization and opsonization.
Neutralization involves blocking toxin and pathogen action.
Opsonization enhances pathogen phagocytosis by coating them with antibodies.

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

Involves destruction of target cells (e.g., large parasites) via non-specific immune cells.
Eosinophils, macrophages, and NK cells bind to antibodies on target cells, releasing enzymes to damage them.

Pathways of Antibody Action

Classical pathway initiated by the binding of antibodies to antigens, forming a complex that activates C1 and leads to further complements.
Complement pathways (Classical, Alternative, Lectin) differ by their initiation mechanism but converge on enhancing immune response.

Clonal Selection and Memory

Clonal selection process ensures that only lymphocytes specific to an antigen are activated and reproduce.
Initial B cell response to infection takes about 1-2 weeks, with IgM being the first immunoglobulin produced.
After the infection, plasma cells die, but memory cells persist for quicker responses upon re-exposure.

Regulation of Complement Pathway

Serum regulatory proteins control the complement system, preventing excessive activation and tissue damage.
Regulation occurs at multiple stages to ensure that complement activity is appropriately terminated.

Adaptive Immunity

Represents the body's third line of defense against pathogens.
Enables recognition and response to specific invaders and products, such as protozoa, fungi, bacteria, viruses, or toxins.
Referred to as acquired or specific immunity, activated when innate immunity is compromised.

Key Players & Components

Antibodies: Proteins generated to neutralize antigens.
Antigens: Substances that elicit an immune response (immunogens).
Lymphocytes: White blood cells, including B-cells and T-cells, essential for adaptive immunity.
Cytokines: Signaling proteins that mediate and regulate immunity.
Complement System: Proteins that enhance the immune response, assisting in the elimination of pathogens.

Cell Activation

B-Cell Receptors (BCRs): Immunoglobulin receptors on B-cells that recognize specific antigens, generally IgM and sometimes IgD.
Interaction between B-cells and T-cells occurs in lymphoid organs such as lymph nodes and the spleen.

Major Adaptive Immune Responses

Humoral: Mediated by antibodies circulating in body fluids.
Cell-Mediated: Carried out by T-cells at a cellular level.

B-Cell Activation Mechanism

Clonal selection occurs when a B-cell encounters a specific antigen, leading to proliferation into plasma cells that produce antibodies.

Complement System & Diseases

Deficiencies in complement proteins can increase susceptibility to infections.
Specific deficiencies correlated with clinical conditions, such as:
- C1, C2, or C4: Linked to collagen vascular disorders.
- C3, C2: Higher infection susceptibility.
- C5 to C9: Increased risk of infections from Neisseria species.

Cell-Mediated Immunity

Provides defense against intracellular microbes and infections that antibodies cannot address.
Mediated by T-lymphocytes, crucial for recognizing antigens from infected cells.

Components of Cell-Mediated Immune System

Helper T Cells (CD4): Activate macrophages, assist B-cell activation, and cytotoxic T-cell activation.
Cytotoxic T Cells (CD8): Responsible for destroying infected host cells and foreign cells.

Immune Response Mechanism

An effective immune response requires distinguishing between self and non-self.
Innate Immunity: Utilizes toll-like receptors (TLRs) to detect microbial components.
Adaptive Immunity: Involves identification, processing, and presentation of antigens using:
- Antibody-antigen Complex: Direct binding of antigens to antibodies.
- Major Histocompatibility Complex (MHC): Essential for T-cells to recognize peptide antigens presented by antigen-presenting cells (APCs).

Major Histocompatibility Complex (MHC)

Also known as the Human Leukocyte Antigen (HLA) system; crucial receptors on lymphocytes and macrophages.
Differentiated into Class I MHC (present on most nucleated cells) and Class II MHC (found mainly on APCs), both key for proper immune function.

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Description

Test your knowledge on the two main types of lymphocytes: B cells and T cells. This quiz will cover the characteristics, functions, and roles of these vital components of the immune system. Understand how they contribute to antigen-specific responses.