MLT GlobeImmunology & Serology: Immune system principles – page 4
257 Immunology & Serology MCQs on Immune system principles with answers and explanations.
Which immunoglobulin is co-expressed with IgM on naive B cells?
Naive B cells co-express IgM and IgD with the same specificity.
Which antibody usually exists as a pentamer?
Secreted IgM is a pentamer joined by J chain. IgA is mostly a dimer in secretions.
Which immunoglobulin class gives the strongest agglutination?
Pentameric IgM has 10 binding sites, allowing it to bridge cells efficiently.
The antigen-binding site of an antibody is made up of:
The binding site is formed by the variable domains of both heavy and light chains.
Which cells synthesize and secrete immunoglobulins?
Plasma cells, terminally differentiated B cells, secrete large amounts of antibody.
In secretions, which antibody usually exists as a dimer?
Secretory IgA is a dimer linked by J chain with a secretory component.
Which immunoglobulin does the fetus produce first?
The fetus produces IgM first and is protected by maternal IgG.
Which pair of immunoglobulins activates the classical complement pathway?
IgM and IgG bind C1q. IgA and IgE do not activate the classical pathway.
How many types of light chain are found in human immunoglobulins?
Kappa and lambda; each molecule has only one type.
In mammals, which organ corresponds to the avian bursa of Fabricius?
B cells mature in the bone marrow. The thymus is where T cells mature.
Which is NOT a human immunoglobulin class?
The five classes are IgG, IgA, IgM, IgD and IgE; IgF does not exist.
IgA differs from other immunoglobulins in that it:
IgA is the main antibody at mucosal surfaces, blocking pathogen attachment.
C1 is activated in the classical pathway by:
C1q binds the Fc of antigen-bound IgG or IgM. Factor B belongs to the alternative pathway.
Which statement about complement is correct?
The alternative pathway is activated by microbial surfaces. The MAC is C5b-9; C3a and C5a are anaphylatoxins.
The membrane attack complex is formed by:
C5b-9 forms the membrane pore. C4b2a is the classical C3 convertase.
Complement proteins in plasma:
Complement circulates as inactive zymogens activated in cascade.
C3a and C5a cause:
C3a and C5a are anaphylatoxins; they cause mast cell degranulation and increased permeability.
What is the main role of C5a in inflammation?
C5a is a strong chemoattractant for phagocytes.
Classical pathway components act in which order?
C1 cleaves C4 then C2, forming C4b2a, which cleaves C3.
Complement enhances phagocytosis mainly through:
C3b coats microbes and binds complement receptors on phagocytes.