MLT GlobeImmunology & Serology: Immune system principles – page 2
257 Immunology & Serology MCQs on Immune system principles with answers and explanations.
Which property does NOT belong to IgM?
IgE, not IgM, sensitizes mast cells in allergy. IgM is the first antibody made, is a strong complement activator, and monomeric IgM is a B-cell receptor.
A key effector role of complement is to:
Complement bound to antibody-coated cells can form the membrane attack complex and lyse them. Phagocytosis is performed by cells, not complement.
What is the main function of MHC class I and class II molecules?
MHC class I presents peptides to CD8 T cells and class II to CD4 T cells. Intracellular signalling is performed by CD3.
Why do antibodies and T-cell receptors bind antigens specifically?
Binding depends on the complementary fit of the binding site to the epitope through non-covalent forces. TCRs lack immunoglobulin light and heavy chains.
The paratope, the antigen-binding site, is found on which molecule?
The paratope is part of the antibody variable region; it binds the epitope on the antigen.
Which statement about IgE is FALSE?
IgE neither crosses the placenta (IgG does) nor activates complement. It binds mast cells, causing allergy and anti-parasite responses.
In a healthy adult, which immunoglobulin class has the highest serum concentration?
IgG makes up about 75–80% of serum immunoglobulin. IgA is second and IgE the lowest.
Breast-fed infants gain protection of the gut from which antibody in colostrum and milk?
Secretory IgA is the main antibody in milk and other secretions, protecting the infant's gut mucosa.
Which statement best describes an antibody?
Antibodies are glycoproteins that migrate mainly in the gamma-globulin region and are formed after exposure to immunogens.
Which immunoglobulin class is present at the lowest serum concentration in normal adults?
IgE is present in trace amounts, much lower than IgD. Most IgE is bound to mast cells and basophils.
After booster vaccination, a switch in immunoglobulin class usually changes antibody from:
In class switching, the variable region is kept but the heavy-chain constant region changes, typically from IgM to IgG.
What is true of kappa and lambda light chains?
Kappa or lambda light chains may pair with any heavy-chain class. Light chains have both variable and constant domains.
Which is NOT true of antibodies?
Antibodies are made by B cells and plasma cells, not T cells.
Which statement about interleukins is FALSE?
Interleukins are signalling proteins that act through receptors; they do not recognize antigens.
What is the main role of lymphokines?
Lymphokines are cytokines secreted by lymphocytes that activate and coordinate other immune cells.
An exaggerated immune reaction to harmless antigen, such as pollen, that damages the host is called:
Hypersensitivity is an excessive response to foreign antigen. Autoimmunity targets self antigen.
Which antibody class triggers immediate allergic reactions?
IgE binds mast cells and basophils; allergen cross-linking releases histamine and other mediators.
Hypersensitivity types I, II and III share which feature?
Types I (IgE), II (IgG/IgM on cells) and III (immune complexes) involve antibodies, whereas type IV is T-cell mediated.
Severe combined immunodeficiency is characterized by defective:
SCID affects both T cells and B-cell (antibody) responses. Selective IgA deficiency is a milder humoral defect.
HIV mainly infects and depletes which cells?
HIV binds CD4 with a chemokine co-receptor and depletes CD4 T cells. Monitoring uses CD4 counts.