Antibody Subtypes Quiz
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Questions and Answers

Which site on the immunoglobulin is responsible for binding with the complement?

  • CH2 (correct)
  • Fc Receptor
  • Heavy chain
  • CH3

What is the primary biological function mediated by the IgG subclass?

  • Phagocytosis
  • Cytokine production
  • Opsonization (correct)
  • Antigen presentation

Which Fc receptor type is characterized by high affinity binding to the Fc portion of Ig?

  • High affinity Fc receptor (correct)
  • Glycosylated Fc receptor
  • Low affinity Fc receptor
  • Multimeric Fc receptor

What is the half-life of IgG in circulation?

<p>20 days (A)</p> Signup and view all the answers

How many sub-classes of IgG are there?

<p>4 (A)</p> Signup and view all the answers

Which part of the IgG is primarily responsible for interactions with Fcγ receptors?

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

Which of the following activities is NOT associated with immunoglobulins?

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

What characteristic of the IgG subclasses allows for their flexibility?

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

What determines the different isotypes of immunoglobulin (Ig) molecules?

<p>Differences in the constant regions of both light and heavy chains (A)</p> Signup and view all the answers

When using a mouse polyclonal Ig as an immunogen in a rabbit, what type of antibodies are produced?

<p>Rabbit anti-mouse isotypic antibodies (B)</p> Signup and view all the answers

Which type of immunoglobulin is present in external fluids like tears and saliva?

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

What does the presence of a transmembrane domain indicate about an immunoglobulin?

<p>It is a membrane Ig (A)</p> Signup and view all the answers

Which immunoglobulin allotype is produced when a mouse strain A Ig is injected into a mouse strain B?

<p>Mouse B anti-mouse A (B)</p> Signup and view all the answers

What role does the lysosome play in the processing of an antigen by a B cell?

<p>It degrades the antigen and BCR. (B)</p> Signup and view all the answers

What facilitates the joining of two monomers in secretory immunoglobulin to form a dimer?

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

How are MHC class II molecules relevant to T follicular cell activation?

<p>They present processed antigens to T follicular cells. (D)</p> Signup and view all the answers

What happens to the B cell after it presents the antigen to a T follicular cell?

<p>It receives signals to proliferate and differentiate. (B)</p> Signup and view all the answers

What is the main role of the intracytoplasmic domain in membrane immunoglobulin?

<p>Anchoring the Ig to the B cell membrane (A)</p> Signup and view all the answers

What is the consequence of T follicular cells recognizing the antigen presented by B cells?

<p>The T cells will release cytokines to assist B cell activation. (A)</p> Signup and view all the answers

Which of the following heavy chain isotypes is not found among the five mentioned?

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

What is the final outcome for activated B cells?

<p>They proliferate to form a clone and differentiate into plasma cells. (C)</p> Signup and view all the answers

What is the role of antibodies produced by plasma cells?

<p>They neutralize pathogens and facilitate their elimination. (D)</p> Signup and view all the answers

Why is the interaction between the B cell and T follicular cell considered crucial?

<p>It ensures a strong and lasting immune response. (B)</p> Signup and view all the answers

What specificity does the T cell receptor (TCR) possess in relation to the antigen presented by B cells?

<p>It recognizes antigen in conjunction with MHC class II molecules. (A)</p> Signup and view all the answers

What is the primary function of maternal IgG in the context of infant health?

<p>To protect the infant from infections for about 3 months after delivery (A)</p> Signup and view all the answers

What condition may arise in an infant due to a deficiency in IgG production after maternal IgG is depleted?

<p>X-linked Bruton immunodeficiency (A)</p> Signup and view all the answers

How does maternal Graves' disease affect the newborn?

<p>Newborn inherits antibodies against TSH receptors from the mother (A)</p> Signup and view all the answers

What major risk does an Rh– mother face when delivering an Rh+ baby?

<p>Sensitization leading to severe anaemia in subsequent pregnancies (C)</p> Signup and view all the answers

What role does FcγRn play in relation to maternal antibodies and the fetus?

<p>It allows the transfer of certain antibodies from mother to infant (B)</p> Signup and view all the answers

What is the consequence of the immune-complexed IgG binding to FcγRIIB?

<p>It inhibits cell functions and can induce apoptosis (C)</p> Signup and view all the answers

Which pathology can be prevented by administering anti-Rh Ig after delivery?

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

What happens to a baby with erythroblastosis fetalis due to Rh incompatibility?

<p>The baby experiences increased bilirubin levels and potential anaemia (B)</p> Signup and view all the answers

Which blood group represents individuals who inherited both enzymes for adding α-N-acetyl-galactosamine and α-D-galactose?

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

What is the primary function of anti-A and anti-B antibodies?

<p>React against sugars present in bacterial cell walls (B)</p> Signup and view all the answers

What is true about IgE in serum?

<p>It can persist for years when bound to FcεRI (C)</p> Signup and view all the answers

Which statement best describes the interaction between IgE and tetrameric FcεRI?

<p>Activation of ITAM sequences occurs after antigen crosslinking (C)</p> Signup and view all the answers

Which blood group is characterized by the absence of both enzymes for adding sugars to substance H?

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

What type of antibodies are primarily involved in the response against carbohydrate antigens?

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

Where are tetrameric FcεRI receptors primarily located in the body?

<p>On basophils and mast cells beneath the skin and mucosa (C)</p> Signup and view all the answers

What can be inferred about T cells from the information provided?

<p>They do not deliver isotype switching signals (D)</p> Signup and view all the answers

Where does affinity maturation occur within the germinal centre?

<p>In the light area with centrocytes (C)</p> Signup and view all the answers

What is the role of the enzyme AID in the germinal centre?

<p>To deaminate cytosine to uracil (A)</p> Signup and view all the answers

What happens to B cells during isotype switching?

<p>They change the class of antibodies produced (C)</p> Signup and view all the answers

Which process allows only B cells producing high-affinity antibodies to survive?

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

What distinguishes centroblasts from centrocytes in terms of their cellular state?

<p>Centroblasts are actively proliferating; centrocytes have exited the cell cycle (D)</p> Signup and view all the answers

Which DNA repair process can occur when uridine is detected during mismatch repair?

<p>Base excision repair (C)</p> Signup and view all the answers

What is the characteristic histological appearance of centroblasts during proliferation?

<p>Dark staining due to abundant nuclear content (D)</p> Signup and view all the answers

Which statement best describes the outcome of hypermutation in centroblasts?

<p>It enhances the affinity of antibodies for the specific antigen (D)</p> Signup and view all the answers

Flashcards

Antigen internalization by B cells

Antigen binds to B cell receptor (BCR) and is internalized into a vesicle that fuses with a lysosome.

MHC class II transport

MHC class II proteins are transported to the cell surface in a vesicle.

Antigen loading onto MHC class II

The processed antigen fragment is loaded onto MHC class II molecule in a vesicle.

B cell antigen presentation

B cells display antigen-MHC class II complexes on their surface.

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Tfh recognition of B cells

T follicular cells (Tfh) recognize the antigen-MHC class II complex displayed by B cells through their TCR.

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Tfh activation of B cells

Activated Tfh cells release cytokines that further activate B cells.

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B cell activation and differentiation

Activated B cells proliferate and differentiate into plasma cells that produce antibodies.

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Antibody affinity

Antibodies have different affinities for the same antigen.

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CH2 region

The constant region of an immunoglobulin (Ig) molecule that interacts with complement proteins.

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CH3 region

The constant region of an immunoglobulin (Ig) molecule that binds to Fc receptors on phagocytes.

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Monomeric Ig

A type of immunoglobulin (Ig) that exists as a single unit.

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Phagocytosis

The process by which immune cells engulf and destroy pathogens.

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Opsonization

A process that helps immune cells recognize and target pathogens by coating them with antibodies.

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Antibody-dependent cellular cytotoxicity (ADCC)

A mechanism by which immune cells kill target cells.

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IgG

A type of immunoglobulin (Ig) that is the most abundant in the blood.

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Hinge region

The flexible region of an immunoglobulin (Ig) molecule that allows for different conformations.

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Immunoglobulin Isotype

Different versions of the same immunoglobulin class, determined by variations in the constant region of heavy chains.

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Immunoglobulin Allotype

Polymorphism in immunoglobulin constant regions, leading to variations within a given isotype.

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Immunoglobulin Idiotype

Variations in the variable region of an antibody, specific to a particular antigen.

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Membrane Immunoglobulin (mIg)

Immunoglobulins found on the surface of B cells, functioning as receptors for antigens.

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Secreted Immunoglobulin (sIg)

Immunoglobulins secreted into the blood and lymph, responsible for humoral immunity.

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Secretory Immunoglobulin (sIg)

Immunoglobulins found in external secretions like mucus, saliva, and tears, providing protection against mucosal pathogens.

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Secretory Component

A component of the secreted IgA dimer, facilitating its transport across mucosal epithelial cells.

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J Chain

A polypeptide chain that joins two immunoglobulin monomers together, forming a dimer, especially in IgA.

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Hypermutation

This process occurs in germinal centers, specifically in the 'dark zone', where rapidly dividing B cells (centroblasts) undergo rapid mutations in their antibody genes.

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Affinity Maturation

In the 'light zone' of the germinal center, B cells (centrocytes) that produce high-affinity antibodies are selected for survival. This process refines the immune response by ensuring that only the most effective antibodies are produced.

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Isotype Switching

This process allows B cells to change the class of antibody they produce. This is important because different antibody classes have different functions in the immune system.

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Centroblast

A rapidly dividing cell type in the germinal center's 'dark zone'. Centroblasts are the primary site of hypermutation.

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Centrocyte

A non-dividing cell type in the germinal center's 'light zone'. Centrocytes have undergone hypermutation and express new BCRs, allowing them to compete for survival based on their antibody affinity.

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AID (Activation-Induced Deaminase)

A key enzyme involved in hypermutation. It deaminates cytosine to uracil, which is then recognized as an error and triggers DNA repair mechanisms, leading to mutations in the antibody genes.

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Mismatch Repair

A DNA repair mechanism where the wrong nucleotide (uracil) is removed and replaced with the correct base. This process plays a critical role in hypermutation.

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Base Excision Repair

A DNA repair pathway where a damaged base (uracil) is removed along with a few surrounding nucleotides. This mechanism is also important for hypermutation.

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What enzyme do people with blood type A inherit?

Individuals with blood type A inherit an enzyme that adds α-N-acetyl-galactosamine to the substance H on red blood cells.

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What enzyme do people with blood type B inherit?

Individuals with blood type B inherit an enzyme that adds α-D-galactose to the substance H on red blood cells.

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What enzymes do individuals with blood type AB inherit?

Individuals with blood type AB inherit both enzymes, allowing them to express both A and B antigens on their red blood cells.

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What enzymes do individuals with blood type O inherit?

Individuals with blood type O do not inherit any of the enzymes that modify the H substance, resulting in only the H substance being expressed on their red blood cells.

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What type of antibodies are anti-A and anti-B?

Antibodies against A and B antigens (anti-A and anti-B) belong to the IgM class, which does not cross the placenta.

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What triggers the production of anti-A and anti-B antibodies?

IgM antibodies are naturally produced in response to sugars found on bacteria in the gut and bronchi.

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What immune response is involved in carbohydrate antigens?

Antibodies against carbohydrate antigens primarily involve IgM and do not trigger isotype switching by T cells.

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What is the function of IgE?

IgE is a monomer antibody that plays a crucial role in allergic reactions and parasitic infections.

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Maternal IgG Transfer

The transfer of maternal IgG from the mother's blood to the fetal circulation through the process of endocytosis and acidification in endosomes.

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X-linked Bruton Immunodeficiency

A genetic disorder where the immune system is unable to produce antibodies due to a deficiency in B cell development. It is usually diagnosed in the first few months of life when the infant is no longer protected by maternal IgG.

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Graves' Disease Transfer

A condition where the mother develops antibodies against thyroid-stimulating hormone (TSH) receptors, which can be passed to the baby through the FcγRn and cause symptoms of hyperthyroidism.

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Hemolytic Disease of the Newborn (HDN)

A condition that occurs when a Rh-negative mother is exposed to Rh-positive fetal blood during pregnancy or delivery, causing the mother to develop antibodies against Rh-positive blood. In subsequent pregnancies, these antibodies can attack the fetus's red blood cells, leading to anemia.

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FcγRn (Fc gamma Receptor Neonatal)

An antibody receptor found on the surface of cells that binds to the Fc region of IgG antibodies.

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FcγRIIB (Fc gamma Receptor IIB)

A low-affinity receptor that binds immune complexes containing IgG. Its activation inhibits cell functions and promotes cell death through apoptosis, playing a role in immune regulation.

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IgG (Immunoglobulin G)

A type of antibody that crosses the placenta and provides passive immunity to the fetus.

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Icterus (Jaundice)

A condition characterized by an excessive buildup of bilirubin in the blood, often caused by hemolytic disease of the newborn.

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Study Notes

Antibody Subtypes

  • Antibodies (immunoglobulins) are crucial for immunity and come in various subtypes (isotypes), each with distinct properties and roles. These five main subtypes are IgG, IgM, IgA, IgE, and IgD.
  • IgG is the most abundant antibody, comprising about 80% of serum immunoglobulins. It's monomeric, long-lived (about 20 days), and can cross the placenta. It's involved in various immune responses.
  • IgM is the first antibody produced in response to an infection. It's a large pentameric structure and is relatively short-lived (5-10 days). It's crucial for complement activation and is found in blood and mucous membranes. It cannot cross the placenta.
  • IgA is the most abundant antibody in secretions (tears, saliva, milk). It's typically a dimeric structure (but can also be monomeric) that's important for mucosal immunity to prevent pathogenic invasion. It is particularly significant in protecting external surfaces such as the gut and respiratory tract. It's also short-lived.
  • IgE is involved in allergic reactions and parasitic infections. It's monomeric and is found in very low concentrations in serum. When IgE attaches to specialized Fc receptors on mast cells and basophils, it triggers the release of inflammatory mediators.
  • IgD is predominantly a membrane-bound antibody, acting as a B cell receptor (BCR). It's monomeric and is found in low levels in the serum. Its exact function in vivo is less well understood than other antibody types.

Antibody Structures

  • Antibodies are composed of two heavy chains and two light chains, forming a Y-shaped structure.
  • The tips of the Y (variable regions) are responsible for binding to specific antigens.
  • The remaining portions (constant regions) of the antibody dictates which other cellular components of the immune system the antibody will activate.
  • The hinge region provides flexibility within the antibody structure. This allows it to bind antigens that are spaced far apart.
  • The constant region (Fc) of the antibody determines the antibody class and mediates interactions with components of the immune system (e.g., complement).
  • Some enzymes (papain and pepsin) can cut the antibody into fragments.
  • These fragmented pieces can be used to study antibody fragments.

Antibody Activation and Affinity

  • Different kinds of antigens activate antibodies in different ways.
  • T-dependent antigen response requires T-helper cells, which allows for somatic mutation and class switching resulting in a high-affinity antibody response. Memory B cells are generated.
  • T-independent antigen response does not require T cells and generates antibodies with lower affinity and short-lived plasma cells.
  • Affinity is the strength of the binding between an antibody and an antigen.
  • A higher affinity results in a greater antibody response.
  • Avidity is the overall strength of binding in an antibody with multiple binding sites. A higher avidity results in stronger overall responses. The number of antigens bound strongly increases with a higher avidity.

Antibody Functions

  • Antibodies can directly neutralize pathogens (toxins and viruses).
  • Antibodies can act as opsonins, enhancing phagocytosis by immune cells.
  • Antibodies can trigger complement activation, leading to pathogen destruction.
  • Antibody-dependent cell-mediated cytotoxicity (ADCC) in which cytotoxin-armed immune cells kill pathogens coated in antibodies.
  • Antibodies can opsonize pathogens, making them more readily ingested by phagocytic immune cells.

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Immunology Lesson 13, 14 PDF

Description

Test your knowledge on different antibody subtypes, including their structures, functions, and roles in immune responses. Dive into the details of IgG, IgM, IgA, IgE, and IgD to understand their significance in immunity.

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