Innate and Adaptive Immune System Review

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Questions and Answers

What is the primary function of B cells?

To produce antibodies that bind to antigens (correct)

To engulf and destroy pathogens through phagocytosis

To release cytokines that signal other immune cells

To directly kill infected cells

Which of the following cytokines is crucial for the development of B cells from hematopoietic stem cells?

IL-2

IL-12

IL-4

IL-7 (correct)

Which stage of B cell development marks the irreversible commitment to becoming a B cell?

Pre-pro B cell

Pro-B cell (correct)

Small lymphocyte

Plasma cell

What are the three professional antigen-presenting cells (APCs)?

Dendritic cells, Macrophages, B cells (B) Signup and view all the answers

What is the primary function of complement system component C3a?

Induction of inflammation (D) Signup and view all the answers

Which of the following correctly describes the relationship between B cells and antibodies?

Antibodies are produced by B cells and have identical antigen-binding sites to the B cell's surface receptors (A) Signup and view all the answers

What is the role of follicular helper T cells in B cell activation?

Follicular helper T cells help B cells to produce antibodies by releasing specific cytokines (A) Signup and view all the answers

Which of the following describes the state of B cells released into circulation?

They are immature and cannot be activated (D) Signup and view all the answers

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

Specificity for particular pathogens (C) Signup and view all the answers

What is the main function of the membrane attack complex (MAC)?

To directly kill pathogens (C) Signup and view all the answers

What is the role of iCOS and iCOS ligand in B cell activation?

They stimulate the T follicular helper cell to secrete cytokines and express CD40L. (B) Signup and view all the answers

Which of the following is NOT a requirement for B cell activation?

Direct stimulation by IL-21 and IL-4. (D) Signup and view all the answers

What is the primary role of plasma cells in the immune response?

To secrete antibodies into the bloodstream. (B) Signup and view all the answers

What is the main function of somatic hypermutation in B cell development?

To modify the antigen-binding site of antibodies, increasing their affinity. (D) Signup and view all the answers

Which of the following cytokines is NOT directly involved in antibody class switching?

IL-10 (D) Signup and view all the answers

What is the primary difference between the early primary response and the late primary response in antibody production?

The early response produces lower affinity antibodies, while the late response produces higher affinity antibodies. (C) Signup and view all the answers

Which of the following is an example of an antibody effector function?

Neutralizing viral particles. (A) Signup and view all the answers

What happens to the antigen specificity of a B cell during class switching?

The B cell retains its specificity for the original antigen but increases its affinity. (C) Signup and view all the answers

What is the primary function of IL-12 in the context of helper T cell differentiation?

IL-12 acts as a polarizing cytokine, influencing the differentiation of helper T cells into either Th1 or follicular helper T cells (Tfh). (A) Signup and view all the answers

Which of the following conditions is most likely to lead to the differentiation of a helper T cell into a Th1 cell?

High levels of both IL-2 and IL-12. (D) Signup and view all the answers

What type of antigen is presented by a B cell after it has bound to the B cell receptor?

Exogenous antigen (D) Signup and view all the answers

What is the role of MHC Class II molecules in antigen presentation by B cells?

MHC Class II molecules are responsible for presenting processed antigens to helper T cells. (B) Signup and view all the answers

Which of the following co-stimulatory molecules expressed on the surface of a B cell is responsible for binding to CD28 on helper T cells?

CD80/86 (B) Signup and view all the answers

What is the role of the CD40-CD40L interaction in the context of B cell activation?

CD40-CD40L interaction is involved in the production of antibodies by B cells. (C) Signup and view all the answers

What is the primary function of iCOSL on B cells?

iCOSL is a co-stimulatory molecule that binds to iCOS on helper T cells, leading to cytokine production. (B) Signup and view all the answers

Within the germinal centers of a lymphoid follicle, which type of helper T cell is most likely to interact with a B cell presenting its antigen?

Tfh (B) Signup and view all the answers

What happens to the antigen after it binds to the BCR on a B cell?

The antigen is internalized by the B cell and processed for presentation to T cells. (C) Signup and view all the answers

Which co-receptor is crucial for B cell activation in the spleen?

CD21 (A) Signup and view all the answers

What is the primary role of the follicular dendritic cells (FDCs) in the lymph node?

To provide a scaffold for B cell maturation. (B) Signup and view all the answers

Which of the following is NOT a characteristic of mature naïve B cells?

Presence in the bone marrow (D) Signup and view all the answers

What is the primary function of the paracortex in the lymph node?

To facilitate T cell activation. (D) Signup and view all the answers

What is the main difference between primary and secondary follicles in the lymph node?

Primary follicles are inactive, while secondary follicles are actively involved in B cell maturation. (C) Signup and view all the answers

Which of the following cells are responsible for presenting antigens to T helper cells in the paracortex?

Dendritic cells (A) Signup and view all the answers

What is the role of Ig-alpha and Ig-beta in the B cell receptor?

They initiate signal transduction pathways. (B) Signup and view all the answers

Which of the following is a key marker for mature naïve B cells?

IgD (B) Signup and view all the answers

Where does the process of B cell development primarily take place?

Bone marrow (B) Signup and view all the answers

What is the main reason why pre-B cells undergo checkpoints during development?

To eliminate B cells that are self-reactive. (A) Signup and view all the answers

What is the role of stromal cells in the bone marrow during B cell development?

They secrete growth factors that stimulate B cell proliferation. (B) Signup and view all the answers

What is the primary role of the medulla in the lymph node?

To contain mature plasma cells. (C) Signup and view all the answers

How do naive B cells typically encounter antigens in the lymph node?

All of the above (D) Signup and view all the answers

What is the primary function of the B cell co-receptors, CD19 and CD21?

To amplify the signal from the BCR. (A) Signup and view all the answers

Which of the following processes occurs in the germinal center of the lymph node?

Affinity maturation and isotype switching. (B) Signup and view all the answers

Which of the following statements accurately describes the role of T helper cells in class switching?

T helper cells provide the necessary cytokines that trigger class switching in B cells. (C) Signup and view all the answers

Which of the following is NOT a cytokine typically involved in class switching?

TNF-alpha (C) Signup and view all the answers

What is the primary function of somatic hypermutation in B cells?

To increase the affinity of antibodies for their antigens through selective mutations. (B) Signup and view all the answers

What is the critical role of follicular dendritic cells in the germinal center?

They present antigen to B cells, allowing them to test their antibody affinity. (C) Signup and view all the answers

How does a B cell with a higher affinity for an antigen survive in the germinal center?

It interacts with follicular helper T cells and receives signals that promote its survival and further differentiation. (A) Signup and view all the answers

Why is T cell help required for B cell differentiation into plasma cells?

T cells provide the necessary cytokines that promote B cell survival and differentiation. (B) Signup and view all the answers

What is the primary function of Th2 cells in relation to class switching?

They promote the production of IgE antibodies, which are important for allergic responses and defense against parasites. (A) Signup and view all the answers

Which of the following correctly describes the role of the dark zone in the germinal center?

It is where B cells undergo somatic hypermutation and lose HLA surface expression. (C) Signup and view all the answers

What is the primary difference between a plasma cell and a memory B cell?

Plasma cells are short-lived, while memory B cells are long-lived. (C) Signup and view all the answers

What does a helper T cell do when it interacts with a B cell?

It provides signals that activate the B cell to differentiate into a plasma cell. (B) Signup and view all the answers

Which of the following is NOT a function of antibodies?

Directly killing pathogens. (D) Signup and view all the answers

Which antibody class is typically the most prevalent in the blood?

IgG (C) Signup and view all the answers

What is the primary function of memory B cells?

They provide long-term immunity by quickly responding to re-exposure to a specific antigen. (B) Signup and view all the answers

Which of the following is a characteristic of plasma cells?

They secrete large quantities of a single type of antibody. (D) Signup and view all the answers

Which antibody class is primarily involved in activating the classical pathway of complement?

IgM (B) Signup and view all the answers

Which antibody class is found in high concentrations in secretions like tears, saliva, and breast milk?

IgA (C) Signup and view all the answers

Which of the following best describes the process of opsonization?

Antibodies coat pathogens, making them more easily recognizable and engulfable by phagocytes. (B) Signup and view all the answers

What is the primary role of Fc receptors in the immune system?

They bind to the stem of antibody molecules. (D) Signup and view all the answers

What is the main difference between naive B cells and memory B cells?

Memory B cells have a higher affinity for their specific antigen than naive B cells. (A) Signup and view all the answers

Which cytokine is known to induce class switching to IgE?

IL-4 (C) Signup and view all the answers

What is the primary function of antibody-dependent cell-mediated cytotoxicity (ADCC)?

To induce apoptosis in infected cells via the activation of NK cells. (C) Signup and view all the answers

Which of the following is NOT a characteristic of IgG?

It is the first antibody class to be produced during an immune response. (B) Signup and view all the answers

What happens when an antigen binds to two or more antibodies on a granulocyte?

The granulocyte becomes activated, releasing inflammatory mediators like histamine. (A) Signup and view all the answers

What is the key characteristic that determines the distinct functions of different antibody classes?

The structure of their constant region. (C) Signup and view all the answers

Which antibody class is primarily involved in inducing degranulation of basophils and mast cells?

IgE (B) Signup and view all the answers

Which of the following statements regarding affinity maturation is CORRECT?

It involves the selection of B cells that express BCRs with higher affinity for the antigen. (C) Signup and view all the answers

Study Notes

Innate Immune System Review

Macrophages and neutrophils are phagocytes, breaking down microbes into smaller components and releasing cytokines
Cytokines are crucial in initiating inflammation and recruiting immune cells to the affected area
Complement system components (e.g., C3a, C3b, C5b) promote inflammation and aid in phagocytosis

T-Cell Response to Antigen Presentation

T cells require antigen presentation by professional antigen-presenting cells (APCs) like dendritic cells and macrophages
Macrophages also help with antigen presentation and the action of helper T-cells
B cells can also present antigens and require helper T-cells
Cytokines like IL-12 influence the development of follicular helper T-cells

B-Cell Function and Development

B cells produce plasma cells, which secrete antibodies
Antibodies are capable of targeting pathogens, microbes, or molecules
B-cell development is influenced by IL-7, from hematopoietic stem cells
B-cells will go through checkpoints before developing into a plasma or memory B-cell

B-Cell Development and Stages

Pre-pro B cells develop from lymphoid precursors
Pro-B-cells become irreversibly committed to B-cell development
B-cells go through immunoglobulin gene recombination to create antibody diversity
Pre-B cells express an immature B cell receptor
Checkpoint #1 in pre-B cells checks if BCR is productive and can bind to antigen or not
Pre-B cells check point #2 for self-reactivity
Immature B cells leave bone marrow to the spleen or lymph nodes
B cell markers change (surface B cell markers)
Stromal cells in bone marrow provides antigens for testing
B-cell receptors associate with disulfide-liked Ig-alpha and Ig-beta

B-Cell Activation

B cells can be activated in lymphatic tissue and by encountering pathogens, or macrophages presenting antigens
Ag binding to the BCR with the help of B cell co-receptors (e.g., CD21)
B cells encounter antigens in the lymph nodes through afferent lymphatics
Activated to plasma or memory b cells
Activation proceeds in the germinal center of lymph nodes
B cells produce antibodies with high affinity during somatic hypermutation
Cytokines secreted by T helper cells (like Tfh cells) influence class switching
B cells will either differentiate into plasma cells (to produce antibodies) or memory B cells (for future immune responses)

Antibody Structure and Function

Antibodies are proteins with two heavy and two light chains
Specific regions (variable) bind to specific antigens
Diverse antibody types provide distinct response strategies
Neutralization, agglutination, opsonization, complement activation, and antibody-dependent cell-mediated cytotoxicity (ADCC) are antibody functions

Antibody Class Switching

Antibodies can change from one type (e.g., IgM) to another (e.g., IgA or IgG) in response to specific signals
Cytokines produced by T helper cells regulate the class switching process in germinal centers
Different antibody classes have different functions and properties (e.g., mucosal immunity, neutralization, or complement activation)

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Description

This quiz covers key aspects of the innate and adaptive immune systems, focusing on phagocyte functions, T-cell responses, and B-cell development. Test your knowledge on cytokines, antigen presentation, and the role of antibodies in immune defense. Perfect for students studying immunology.