Lecture 6 Quiz: B Cells 2 Flashcards
Which of the following statements does not describe an antibody (Ab) effector function? a. Mediate cytotoxicity by the process known as antibody-dependent cellular cytotoxicity (ADCC). b. Antibodies polymerise on the surface of target cells forming pores which induces their lysis. c. Antibodies mediate the neutralisation and opsonisation of microbes. d. Activate complement.
Antibodies polymerise on the surface of target cells forming pores which induces their lysis. … Ab can mediate activation of the Membrane Attack Complex [MAC], however the formed pore results from the polymerisation of C9, not of Ab.
Complete the following sentence. The most common antibody isotype found in serum, with roles in opsonisation, complement activation and ADCC as well as neonatal immunity is….
IgG. … Approximately 80% of normal serum Ab is IgG. IgG can recruit complement via interaction with C1q or C3. Engagement of IgG to Fc receptors on macrophages and NK cells can also induce phagocytosis and ADCC respectively. Furthermore, IgG can cross the placenta providing neonatal immunity.
Complete the following sentence. During an immune response, the first antibody isotype expressed is……….
IgM. … IgM is rapidly expressed as it does not require isotype switching as other antibody isotypes do.
How does the concept of affinity differ from avidity?
Affinity refers to the strength of interaction of one binding site whereas avidity is the combined strength of multiple binding sites. …. If an antibody’s binding site interacts strongly with its corresponding antigen, this antibody has high affinity. The more antigen binding sites an antibody has, the higher the avidity.
Complete the following sentence. The antibody isotype which displays the highest avidity due to its pentameric form, and is capable of complement recruitment corresponds to…..
IgM. …. NOT IgA: Despite having high avidity due to being polymeric this antibody has lower avidity than IgM, and its major role is neutralising bacteria, viruses and toxins.
The predominant antibody isotype in external secretions that can neutralise pathogens and toxins and prevent their interaction with mucosal surfaces is:
IgA … IgA predominates in breast milk, saliva, tears and mucus and is capable of binding bacteria, viruses and toxins, preventing their association with specific target sites.
The antibody isotype that provides immunity against helminths and is capable of sensitising mast cells resulting in the induction of an allergic response is:
IgE .. IgE predominates in anti-helminth immune responses and its binding to surface FcRe induces mast cell degranulation and allergic reactions such as anaphylaxis, eczema, asthma and hay fever.
Which of the following statements is characteristic of isotype switching? a. A process required for expression of IgM but not for expression of IgG, IgA or IgE. b. Is a reversible change in DNA that permits the transmembrane expression and secretion of IgG, IgA or IgE. c. Occurs in the germinal centre and depends on cytokine signalling and CD40 ligation. d. All of the above are correct.
Occurs in the germinal centre and depends on cytokine signalling and CD40 ligation. T follicular helper cells secrete cytokines that in conjunction with CD40 ligation provide the necessary signals to B cells to enable the most appropriate class switching according to pathogen triggering the immune response.
QUESTION 9 In addition to CD40 ligation, which of the statements below identify a cytokine that induce a correct antibody isotype?
a. IFN-gamma induces an IgA switch.
b. IL-4 or IL-13 induces an IgE switch.
c. TGF-beta induces an IgG switch.
d. All of the above are correct
b. IL-4 or IL-13 induces an IgE switch. …. cytokines IL-4 or IL-13 can induce an IgE switch.
Complete the following sentence. A feature which does not describe patients presenting with x-linked hyper IgM syndrome is………. a. T cells that do not express CD40L. b. B cells that cannot undergo isotype switching. c. They present normal levels of all antibody isotypes, however only IgM is functional. d. Are highly susceptible to infections with pyogenic bacteria.
They present normal levels of all antibody isotypes, however only IgM is functional. … as this statement is not true. Individuals with x-linked hyper IgM syndrome lack IgG, IgA or IgE expression due to the inability of their B cells to undergo isotype switching.
