MLT GlobeImmunology & Serology: Immune system principles – page 8
257 Immunology & Serology MCQs on Immune system principles with answers and explanations.
Before a helper T cell can help a B cell make antibody, the helper T cell itself must first be activated by:
T cells recognise only processed peptide presented on MHC. Dendritic cells and macrophages present antigen on MHC II to CD4 cells, which then activate B cells.
How do cytotoxic (CD8+) T lymphocytes kill virus-infected cells?
CD8+ T cells recognise antigen on MHC class I and deliver perforin and granzymes that trigger apoptosis. B cells, not T cells, become plasma cells.
Which of these is NOT part of innate (non-specific) immunity?
Antibodies in breast milk are specific and represent naturally acquired passive immunity. Lysozyme, commensal flora and gastric acid are innate barriers.
When antibody-coated target cells are lysed by complement, which component polymerizes to form the pore in the membrane?
C5b-8 inserts into the membrane and recruits many C9 molecules, which polymerize into a pore. C1q binds antibody and C3b opsonizes.
A T cell ignores a soluble protein that a B cell recognizes. The best explanation is that the T-cell receptor:
TCRs are MHC-restricted, recognizing processed peptides presented by MHC. Antibodies and BCRs bind free, native antigen directly.
The antibodies produced in a normal immune response to a protein antigen are NOT:
A natural response is polyclonal, so antibodies vary in sequence and specificity. A single sequence is a feature of monoclonal antibodies.
What is the role of the J chain in immunoglobulins?
Plasma cells produce the J chain, which joins IgM pentamers and IgA dimers and enables transport across epithelium.
Which statement about antibody structure is FALSE?
Class (isotype) depends on the heavy chain; kappa or lambda light chains occur in every class. IgG has two identical binding sites.
The CD3 complex associated with the T-cell receptor:
CD3 (formerly T3) transmits activation signals when the TCR binds peptide–MHC.
Which statement about the CD4 and CD8 markers is FALSE?
Mature peripheral T cells express either CD4 or CD8; double-positive cells occur only in the thymus.
What do the T-cell receptor and antibody have in common?
Both BCR and TCR are membrane receptors. Only antibodies are secreted, switch class or contain J chains.
A single immunoglobulin-type domain, found in antibodies and TCRs, contains roughly how many amino acids?
Immunoglobulin domains are about 110 amino acids, folded and stabilized by a disulfide bond.
Laboratory diagnosis of most systemic and organ-specific autoimmune diseases relies mainly on detecting:
Autoantibodies (e.g., anti-dsDNA, anti-TPO, AChR antibodies) are measurable serum markers of lost self-tolerance, even in diseases where tissue damage is largely T-cell mediated, such as type 1 diabetes and rheumatoid arthritis.
Which HLA allele is most strongly associated with rheumatoid arthritis?
HLA-DR4 (shared epitope) is linked to RA. HLA-B27 is linked to ankylosing spondylitis and DQ2 to coeliac disease.
Immunizing a rabbit with human albumin produces antibodies of different specificities because albumin:
Large protein antigens have multiple epitopes, each stimulating different B-cell clones, producing a polyclonal response.
Which statement about the T-cell receptor is FALSE?
Classes I and II describe MHC molecules; TCRs are classified as alpha-beta or gamma-delta.
A mature naive B cell has on its surface:
Naive B cells express monomeric IgM (with IgD) of a single specificity as the B-cell receptor.
Clonal selection theory states that:
Each lymphocyte has a single pre-existing receptor specificity; antigen selects and expands matching clones.
Raised specific antibody in a newborn's cord blood suggests congenital infection when the antibody class is:
IgM does not cross the placenta, so it must come from the fetus. IgG may be maternal.
Secretory IgA resists degradation on mucosal surfaces because it:
Polymeric Ig receptor transports IgA across epithelium and a part remains as secretory component protecting it.