Immunology Quiz on Antibodies and T Cells
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Questions and Answers

What is the primary characteristic of monoclonal antibodies?

  • Produced by a single clone of B-cell (correct)
  • Have diverse antigenic specificities
  • Only used for research purposes
  • Produced by multiple clones of B-cells

Which immunoglobulin type has the most binding sites?

  • IgG
  • IgA
  • IgE
  • IgM (correct)

What mechanism allows B cells to produce antibodies of different heavy-chain classes?

  • Clonal expression
  • Class switching (correct)
  • Clonal selection
  • Affinity maturation

How do dendritic cells activate T cells?

<p>By binding to CD28 receptors with B7 molecules (A)</p> Signup and view all the answers

Which receptor type is primarily found on naive B lymphocytes acting as an antigen receptor?

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

What type of epitope can T cells recognize?

<p>Linear epitopes (B)</p> Signup and view all the answers

What type of antigen receptor is present on B-lymphocytes?

<p>Membrane-bound immunoglobulin (B)</p> Signup and view all the answers

Which of the following correctly describes the structure of an immunoglobulin?

<p>It consists of two heavy and two light chains forming a 'Y' shaped structure. (C)</p> Signup and view all the answers

Which statement correctly describes T cell receptors (TCR)?

<p>TCR recognizes processed peptide antigens displayed on APCs. (B)</p> Signup and view all the answers

What role do Ig alpha and beta play in the immune response?

<p>They serve as signal transduction proteins. (D)</p> Signup and view all the answers

What distinguishes B cell receptors (BCR) from T cell receptors (TCR) in terms of antigen recognition?

<p>BCR can recognize a wider range of molecules than TCR. (C)</p> Signup and view all the answers

How many constant domains do the heavy chains of an immunoglobulin contain?

<p>3 constant domains (B)</p> Signup and view all the answers

What are the two main regions of an antigen receptor (AR)?

<p>Variable region and constant region (B)</p> Signup and view all the answers

What component is NOT part of the T cell receptor (TCR) signaling complex?

<p>CD4 (A)</p> Signup and view all the answers

How is the immune repertoire defined?

<p>Total number of distinct lymphocyte clones (A)</p> Signup and view all the answers

What is the purpose of the constant region of an antigen receptor?

<p>Provides structural integrity and effector functions (C)</p> Signup and view all the answers

Which type of epitope does a B-cell recognize?

<p>Both linear and conformational epitopes (A)</p> Signup and view all the answers

What defines a linear epitope?

<p>It is represented by a sequence of adjacent amino acids. (B)</p> Signup and view all the answers

Which form of antigen recognition is unique to TCR compared to BCR?

<p>Recognition of processed peptide antigens (C)</p> Signup and view all the answers

What is the function of the hinge region in immunoglobulins?

<p>To allow flexibility and movement. (A)</p> Signup and view all the answers

Which of the following statements is true regarding antigen receptors on lymphocytes?

<p>Antigen receptors are attached to other molecules for signaling. (C)</p> Signup and view all the answers

What is the main feature that distinguishes the Fab region from the Fc region in immunoglobulins?

<p>Fab region includes the light chain. (B)</p> Signup and view all the answers

Which chain type primarily determines the class or isotype of an antibody?

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

Which statement about CDR3 is correct?

<p>CDR3 has the highest variability among hypervariable regions. (A)</p> Signup and view all the answers

Which protein forms along with membrane immunoglobulin to create the B-cell receptor (BCR)?

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

The antigenic determinant recognized by antibodies is referred to as what?

<p>Epitope (C)</p> Signup and view all the answers

What type of light chains are found in immunoglobulins?

<p>Kappa and lambda (C)</p> Signup and view all the answers

The hinge region in immunoglobulins primarily provides what function?

<p>Flexibility between the Fab and Fc regions (B)</p> Signup and view all the answers

Which of the following statements about T-cell receptors (TCR) is true?

<p>Each TCR chain has both a constant and a variable domain. (D)</p> Signup and view all the answers

Which immunoglobulin class has the highest concentration in serum?

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

What are the primary components of the TCR complex?

<p>TCR, CD3, ζ protein (C)</p> Signup and view all the answers

Which two classes of immunoglobulin serve as antigen receptors on naïve B-lymphocytes?

<p>IgM &amp; IgD (D)</p> Signup and view all the answers

What is the role of CD4 and CD8 in relation to the TCR?

<p>They enhance the signaling of TCR. (C)</p> Signup and view all the answers

What does the term 'affinity' refer to in the context of antibodies?

<p>The strength with which an antibody binds to an epitope (C)</p> Signup and view all the answers

Which process allows B-lymphocytes to change the class of antibody they produce?

<p>Heavy chain class switching (B)</p> Signup and view all the answers

What happens to the affinity of antibodies during secondary immune responses?

<p>It increases due to affinity maturation. (B)</p> Signup and view all the answers

Which of the following best describes avidity in relation to antibodies?

<p>The total strength of multiple bindings to an antigen (C)</p> Signup and view all the answers

Flashcards

Antigen Specificity

The ability of an antigen receptor (AR) to bind to a specific antigen. It is determined by the variable region of the AR, which differs between lymphocytes.

Immune Repertoire

The total number of distinct lymphocyte clones in an organism. It reflects the diversity of antigens that the immune system can recognize.

B-cell Receptor (BCR)

A transmembrane protein on the surface of B lymphocytes that serves as the antigen receptor. It is a membrane-bound immunoglobulin (antibody) that can directly bind to antigens.

T-cell Receptor (TCR)

A transmembrane protein complex on the surface of T lymphocytes that serves as the antigen receptor. It recognizes peptide antigens presented by MHC molecules on antigen-presenting cells (APCs).

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Variable Region

The part of an antigen receptor (AR) that varies between different lymphocytes, allowing them to recognize different antigens.

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Constant Region

The part of an antigen receptor (AR) that is constant across different lymphocytes of the same type. It provides structural integrity and effector functions.

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Affinity

The ability of an antibody to bind to its target antigen with strong affinity. It is influenced by the strength of interactions between the antibody's variable region and the antigen.

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Avidity

The overall strength of binding between an antibody and its antigen, considering multiple binding sites. It reflects both affinity and the number of binding sites.

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What are epitopes?

Small, specific region on an antigen recognized by antibodies.

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What are linear epitopes?

Linear epitopes are a sequence of amino acids that are adjacent to each other and recognized by T cells.

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What are conformational epitopes?

Conformational epitopes are formed by non-adjacent amino acids that fold into a specific 3D structure, recognized by B cells.

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What are the signal transduction proteins of TCR?

CD3 and zeta (ζ) proteins located on the surface of T cells that are responsible for signal transduction (activating the cell) upon antigen recognition.

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What are Ig𝞪 and Ig𝞫?

Ig alpha and beta are proteins on the surface of B cells responsible for signal transduction (activating the cell).

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What is the structure of an immunoglobulin?

Y-shaped structure composed of four polypeptide chains (two heavy and two light chains), with variable and constant domains.

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What is the hinge of an immunoglobulin?

The hinge region is a flexible area on the immunoglobulin that allows for bending and flexibility, enabling the antibody to bind to different antigens.

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What is the Fab fragment?

The part of the immunoglobulin that binds to the antigen.

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Heavy Chain

A structural component of the antibody, composed of two identical heavy chains linked by disulfide bonds. Each heavy chain has three domains: one variable region (VH) and three constant regions (CH1, CH2, CH3).

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Light Chain

A structural component antibody, composed of two identical light chains linked by disulfide bonds. Each light chain has two domains: one variable region (VL) and one constant region (CL).

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Fab Region

A region on an antibody composed of parts of the variable regions of both the heavy and light chains. It forms the antigen-binding site, allowing the antibody to recognize and bind to specific antigens.

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Fc Region

A region on an antibody composed of the constant regions of the heavy chains. It interacts with other immune cells and molecules, mediating various effector functions such as complement activation and antibody-dependent cell-mediated cytotoxicity.

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Hinge Region

A flexible region in the antibody connecting the Fab regions to the Fc region. It allows for flexibility in the antibody's structure, which is important for antigen binding and effector functions.

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Membrane Immunoglobulin

The form of immunoglobulins that are displayed on the surface of B lymphocytes, acting as the B-cell receptor (BCR).

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Epitope

The part of an antigen that binds to the antigen-binding site on an antibody.

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What is an IgM antibody?

A type of antibody with 10 binding sites, found in the blood and involved in the initial immune response.

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What is an IgA antibody?

A type of antibody with 4 binding sites, found in bodily fluids and involved in mucosal immunity.

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What are monoclonal antibodies?

Antibodies produced by a single clone of B-cells, all recognizing the same antigen.

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What is class switching?

The process where a B-cell switches from producing one type of antibody to another, like IgM to IgG.

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What is CD3?

A protein receptor on T cells that is involved in signal transduction when the TCR binds an antigen.

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What is the CDR3 region?

The most variable region of the T cell receptor (TCR), responsible for recognizing specific antigens.

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What is the TCR complex?

The T cell receptor (TCR) and its associated proteins CD3 and ζ (zeta) form the TCR complex. CD3 and ζ are responsible for transmitting signals into the T cell upon antigen recognition.

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What are CD4 and CD8?

CD4 and CD8 are co-receptors that bind to non-polymorphic regions of MHC molecules (MHCII or MHCI, respectively). They are crucial for proper T cell activation.

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What determines the immunoglobulin class?

The type of heavy chain (μ, δ, γ, ε, α) present in an immunoglobulin determines its class or isotype. There are 5 major classes: IgM, IgD, IgG, IgE, and IgA. Each class has unique functions and properties.

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Which immunoglobulin is the most abundant in serum?

IgG is the most abundant immunoglobulin in the serum. It plays a major role in humoral immunity by neutralizing pathogens and activating complement.

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What is the function of IgD?

IgD acts as a membrane-bound receptor on naïve B lymphocytes. It is involved in B cell activation, but its exact function is still being investigated.

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Which immunoglobulins are found on naïve B lymphocytes?

Naïve B lymphocytes express both IgM and IgD as surface receptors. These antibodies are involved in recognizing antigen and initiating B cell activation.

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What is heavy chain class switching?

Heavy chain class switching is a process where B cells change the class of antibodies they produce, while keeping their antigen specificity. Initially, IgM is produced, and later it can switch to other classes like IgG, IgA, and IgE.

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Study Notes

Antigen Recognition

  • Antigen recognition is a process where lymphocytes recognize antigens using receptors.
  • B-lymphocytes have antigen receptors of the immunoglobulin (Ig) protein family.
  • T-lymphocytes have antigen receptors known as T cell receptors (TCR).
  • B cell receptors (BCRs) recognize native proteins, carbohydrates, lipids and nucleic acids.
  • T cell receptors (TCRs) recognize processed peptide antigens displayed on antigen-presenting cells (APCs) with MHC.
  • Both B and T cell receptors have variable and constant regions within their structures.
  • The variable regions allow for unique antigen binding.
  • The constant regions provide structural stability and effector functions.

Immune Repertoire

  • Each lymphocyte has unique antigen specificity.
  • The total number of distinct lymphocyte clones is called the immune repertoire.
  • The immune repertoire is crucial for recognizing a wide range of antigens.

Learning Questions - Antigen Receptors

  • Structural and functional similarities and differences in antigen receptors on B and T lymphocytes.
  • Molecular structure of membrane immunoglobulins and T cell receptors, along with expression mechanisms.
  • Explanation of antibody "class" and "subclass", including heavy chain class-switching and affinity maturation.
  • Explanation of affinity and avidity in the context of antibody-antigen interactions.
  • Details of monoclonal antibodies.

Epitopes

  • Epitopes are small areas on antigens that antibodies can recognize.
  • Linear epitopes are adjacent amino acids in a sequence.
  • Conformational epitopes are non-adjacent amino acids brought together by folding.

B Cell Receptor (BCR)

  • BCRs consist of membrane Ig (mIg) and associated proteins (Igα and Igβ).
  • BCR binding to antigens initiates B-cell activation.

T Cell Receptor (TCR)

  • TCRs are composed of an alpha (α) and beta (β) chain.
  • Each chain has a constant and variable (V) region, with the variable regions having three complementarity-determining regions (CDRs).
  • TCRs bind to antigen fragments presented by MHC molecules on antigen-presenting cells.
  • CD3 and ζ molecules are essential proteins for signal transduction following TCR antigen recognition.

TCR Complex

  • The TCR complex comprises TCR, CD3, and ζ proteins.
  • CD3 and ζ proteins transmit signals after TCR antigen recognition.
  • CD4 and CD8 are co-receptors that bind to non-polymorphic regions of either MHC I or MHC II proteins. They enhance the TCR signaling cascade.

Antibody Class and Subclass

  • Antibody class/isotype depends on the type of heavy chain (μ, δ, γ, ε, α).
  • There are five major antibody classes: IgM, IgD, IgG, IgE, and IgA. Each has unique physical and biological properties.
  • The concentration of each antibody in the serum varies.

Heavy Chain Class Switching

  • B lymphocytes initially produce IgM, but can switch to different classes (e.g., IgG, IgA, etc.) after encountering antigen.
  • Antigenic specificity does not change during class switching.

Antibody Affinity and Avidity

  • Affinity is the strength of binding between an antibody and a single epitope.
  • Avidity is the overall strength of binding of an antibody to several epitopes on an antigen.

Antibody Affinity Maturation

  • Antibodies in the initial immune response (primary) exhibit low affinity.
  • Repeated encounters with antigen (secondary response) lead to the production of antibodies with higher affinity (affinity maturation).

Monoclonal Antibodies

  • Antibodies produced by a single B-cell clone, thus having a single antigenic specificity.
  • Widely used for diagnostic and therapeutic purposes.

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Antigen Recognition Notes (2023-2024) PDF

Description

Test your knowledge on antibodies and T cell mechanisms in this comprehensive immunology quiz. Explore the roles of different immune cells, recognize key antibody characteristics, and understand how the immune response is activated. Perfect for students studying advanced biology or health sciences.

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