B Lymphocytes lecture

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Questions and Answers

What are B cells?

  • Cells responsible for blood clotting
  • A type of lymphocyte that produces antibodies (correct)
  • Cells that directly kill pathogens
  • A class of RBC

Where do B cells develop in birds and mammals?

  • In the thymus for both
  • In the bursa of fabricus in birds and bone marrow in mammals (correct)
  • In the spleen for both
  • In the lymph nodes for mammals and birds

Where do B cells become activated?

  • In the thymus
  • In the blood stream
  • In secondary lymphoid organs like lymph nodes or the spleen (correct)
  • In the bone marrow

How do B cells become activated?

<p>Through antigen recognition by B cell receptors and co-stimulatory signals (B)</p> Signup and view all the answers

What is the co-stimulatory signal for B cell activation?

<p>Binding of CD40 on B cells to CD40L (B)</p> Signup and view all the answers

How do B cells react to T-independent antigens or T-dependent antigens?

<p>T-independent antigens directly activate B cells, T-dependent antigens require helper T cells (B)</p> Signup and view all the answers

What’s the main difference in B cell activation by T-dependent and T-independent antigens?

<p>T-depending activation requires co-stimulation and produces stronger, longer lasting responses (B)</p> Signup and view all the answers

Why do B cells depend on T helper cells during T-dependent responses?

<p>T helper cells produce cytokines and co-stimulators signals needed for activation (A)</p> Signup and view all the answers

Define the B cells’ primary immune response

<p>The initial response with a lag phase, mainly producing IgM (B)</p> Signup and view all the answers

Define the B cells’ secondary immune response

<p>A rapid, strong response characterized by memory cell activation and IgG production (B)</p> Signup and view all the answers

Compare the B cell secondary and primary immune response

<p>The secondary response is faster, stronger and produces higher-affinity antibodies than the primary response (C)</p> Signup and view all the answers

Explain antibody diversity

<p>Diversity arises from somatic recombination of V,D, and J gene segments in B cells (D)</p> Signup and view all the answers

What do you understand by B cell clonal selection?

<p>Selection and proliferation of B cells specific to an antigen (B)</p> Signup and view all the answers

Following activation of B cells, what does the differentiation pathway look like?

<p>Activated B cells differentiate into plasma and memory cells (D)</p> Signup and view all the answers

What’s the last stage of B cell differentiation?

<p>Differentiation into plasma cells that secrete antibodies (A)</p> Signup and view all the answers

What happens in the germinal centers following B cell activation?

<p>B cells undergo affinity maturation, isotope switching, and memory cell formation (C)</p> Signup and view all the answers

Which immunoglobulins are produced first in the primary response?

<p>IgM (D)</p> Signup and view all the answers

What is B cell isotope switching?

<p>Changing the antibody heavy chain constant region to produce different immunoglobulin classes (C)</p> Signup and view all the answers

What is B cell affinity maturation?

<p>A selection of B cells producing antibodies with increased binding affinity due to somatic hypermutation (A)</p> Signup and view all the answers

What is the role of cytokines in B cell isotype switching?

<p>They regulate isotype switching to immunoglobulin classes like IgG, IgA and IgE (D)</p> Signup and view all the answers

In which immune response, primary or secondary, are high-affinity antibodies produced?

<p>Secondary immune response (B)</p> Signup and view all the answers

How do memory B cells develop?

<p>Through activation in germinal centers during T-dependent responses (B)</p> Signup and view all the answers

What role do antibodies play in pathogen elimination?

<p>Binding antigens to neutralize pathogens and mediate effector functions like phagocytosis and complement activation (B)</p> Signup and view all the answers

What’s the structure of an immunoglobulin molecule ?

<p>A heterodimer with two heavy chains and two light chains linked by disulfide bonds (C)</p> Signup and view all the answers

Name the classes of immunoglobulins you know

<p>IgM, IgA, IgG, IgE, IgD</p> Signup and view all the answers

Which part of the immunoglobulin molecule is responsible for antigen binding?

<p>The variable regions of the light and heavy chains (Fab) (C)</p> Signup and view all the answers

Which part of the immunoglobulin molecules is responsible for inducing ADCC by NK cells?

<p>The Fc region (C)</p> Signup and view all the answers

Which immunoglobulin is responsible for protection of body surfaces?

<p>IgA (A)</p> Signup and view all the answers

Which immunoglobulins can be found as receptors on B cells?

<p>IgM and IgD (B)</p> Signup and view all the answers

What is the biological function of immunoglobulin D (IgD)

<p>To serve as a receptor on naive B cells along IgM (A)</p> Signup and view all the answers

Which class of immunoglobulin is known for its role in allergic reactions?

<p>IgE</p> Signup and view all the answers

Which immunoglobulin is found in abundance in serum?

<p>IgG</p> Signup and view all the answers

What clinical samples are available for antibody detection?

<p>Blood serum, saliva and tears</p> Signup and view all the answers

Which immunoglobulin, in free form, is always found as a pentamer?

<p>IgM</p> Signup and view all the answers

What is the role of secretory component in secretory IgA?

<p>To protect IgA from proteolytic enzymes and facilitate transport across mucosal epithelia (C)</p> Signup and view all the answers

Serum is a mixture of antibodies called ____?

<p>Polyclonal antibodies (B)</p> Signup and view all the answers

What is the use of monoclonal antibodies in human and veterinary medicine?

<p>Diagnosis of therapy of diseases, including cancer and autoimmune disorders (A)</p> Signup and view all the answers

What is immune tolerance?

<p>The immune system’s ability to distinguish between self and non-self and avoid attacking self-tissues (B)</p> Signup and view all the answers

How do regulatory T cells participate in immune tolerance?

<p>By suppressing the activation of immune cells that could react to self-antigens (D)</p> Signup and view all the answers

Where does central tolerance take place?

<p>In the bone marrow and thymus (C)</p> Signup and view all the answers

Where does peripheral tolerance take place?

<p>In secondary lymphoid organs and tissues throughout the body (A)</p> Signup and view all the answers

The development of B cells is divided into three stages, what are these three stages?

<p>Maturation, activation and Differentiation</p> Signup and view all the answers

Match to the appropriate description of the B cells stages

<p>Maturation = Generation of mature immunocompetent B lymphocytes Activation = Contact of B lymphocytes with specific antigens Differentiation = Activated B cells become plasma cells that produce antibodies or become memory B cells Freebie = Freebie</p> Signup and view all the answers

What type of T-independent antigens directly activate B cells by polyclonal activation?

<p>TI-1 antigens (C)</p> Signup and view all the answers

Which receptors are TI-1 antigens recognized by for the activation of B cells?

<p>BCR and TLR (D)</p> Signup and view all the answers

How do TI-2 antigens primarily activate B cells?

<p>By cross-linking multiple membrane Ig receptors (C)</p> Signup and view all the answers

Which characteristic distinguishes TI-1 antigens from TI-2 antigens?

<p>TI-1 antigens activate B cells non-specifically (D)</p> Signup and view all the answers

Which mechanism is NOT involved in the activation of B cells by TI-1 antigens?

<p>Engagement of T cell help (A)</p> Signup and view all the answers

What role do the Igalpha and Igbeta chains play in B cell activation?

<p>They transduce signals critical for B cell activation through their ITAM motifs.</p> Signup and view all the answers

What factors influence the kinetics of a primary immune response?

<p>Factors include the nature of the antigen, administration route, presence of adjuvants, and species of the individual.</p> Signup and view all the answers

Why is the cytoplasmic tail of B cell receptors insufficient for signal transduction?

<p>The BCR's short cytoplasmic tail is too short to transduce signals effectively on its own.</p> Signup and view all the answers

How do ITAM motifs contribute to B cell signaling?

<p>ITAM motifs in Igalpha and Igbeta chains become phosphorylated upon activation, initiating signaling cascades.</p> Signup and view all the answers

What distinguishes the roles of antigens in T-independent versus T-dependent B cell activation?

<p>T-independent antigens directly activate B cells, while T-dependent antigens require help from T helper cells.</p> Signup and view all the answers

Math the definition to each of the events during lag time.

<p>Clonal selection = Selection of B cells with specificity to foreign antigens Clonal expansion = Increase in number of antigen specific cells Differentiation = Development of plasma cells and memory cells Production of antibodies = Mostly IgM and IgG produced</p> Signup and view all the answers

Flashcards

TI-1 antigen

A type of antigen that activates B cells non-specifically, acting as a mitogen.

TI-2 antigen

An antigen that activates B cells by causing many B cell receptors to clump together.

Mitogen

A substance that stimulates cell division, including B cell division.

BCR

A type of receptor on the surface of B cells that recognizes antigens.

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TI Antigen

Antigen that directly activates B cells, divided into TI-1 and TI-2.

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BCR Signal Transduction

B cell receptors (BCRs) bind antigens, but they lack a long enough cytoplasmic tail to trigger signaling. Instead, Igalpha and Igbeta chains, with their ITAMs (immunoreceptor tyrosine-based activation motifs), are responsible for signal transduction.

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ITAM

ITAM stands for "immunoreceptor tyrosine-based activation motif". They are short cytoplasmic tails found on Igalpha and Igbeta chains. The ITAMs play a crucial role in activating signaling pathways within the B cell.

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Primary Immune Response Kinetics

The speed and strength of a primary immune response depends on various factors like the nature of the antigen, the route of administration (vaccine or infection), the presence of adjuvants, and the species of the individual.

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Antigen Nature & Immune Response

The type of antigen (e.g., protein, carbohydrate, lipid) significantly influences the immune response. Some antigens generate a stronger, faster response than others.

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Administration Route & Immune Response

The way an antigen is introduced (vaccine or infection) impacts the immune response. For example, intramuscular injections might elicit different responses than oral administration.

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