MLT GlobeImmunology & Serology: Immune system principles – page 5
257 Immunology & Serology MCQs on Immune system principles with answers and explanations.
Which statement about complement is correct?
Complement proteins are mostly made by the liver and circulate inactive.
Which feature characterizes acquired immunity?
Adaptive immunity is specific, has memory and discriminates self from non-self.
The main advantage of passive immunization over active immunization is that it:
Preformed antibodies protect at once but are short-lived.
Which is a feature of active acquired immunity?
Active immunity generates memory cells and lasts long. Maternal transfer and antibody injection are passive.
Giving diphtheria antitoxin to a patient provides:
Antitoxin provides preformed antibodies, giving immediate but temporary passive protection.
Plasma cells arise from:
Activated B cells differentiate into plasma cells.
Memory cells develop from:
Both B and T lymphocytes form memory cells.
Which is an example of natural passive immunity?
Maternal IgG crossing the placenta is natural passive immunity. Recovery from infection gives natural active immunity.
Which cells shut down immune responses after antigen is cleared?
Regulatory T cells suppress responses through IL-10 and TGF-beta.
Which cytokine is secreted by T cells and activates macrophages and NK cells?
Interferon-gamma is produced by Th1 and NK cells and activates macrophages.
Which is NOT a cytokine?
Colistin is a polymyxin antibiotic; the others are cytokines.
Lymphokines are best defined as:
Lymphokines are lymphocyte-derived cytokines, including many interleukins and interferon-gamma.
In Rh haemolytic disease of the fetus and newborn, which maternal immunoglobulin class crosses the placenta to destroy fetal red cells?
Only IgG is actively transported across the placenta via FcRn. Anti-D IgM, though produced first, is too large to cross.
The 'magic bullet' concept of targeted therapy, delivering a drug or toxin only to cells bearing a chosen antigen, is realised using:
Monoclonal antibodies bind a single epitope and can be conjugated to drugs, toxins or radionuclides, directing them to target cells such as tumours.
Immunological tolerance is best defined as:
Tolerance is antigen-specific non-reactivity (e.g. to self), while responses to other antigens remain intact; general failure is immunodeficiency.
Which immunoglobulin is the first produced in a primary immune response and is the most efficient at activating complement?
IgM, a pentamer with ten binding sites, appears first after new exposure. A single IgM bound to an antigen can activate C1, whereas IgG needs two molecules close together.
Which cell surface marker is most characteristic of mature helper T lymphocytes?
Helper T cells express CD3 and CD4 and recognise antigen presented on MHC class II. CD8 marks cytotoxic T cells, CD19 marks B cells and CD56 marks NK cells.
Which marker is a pan-B-cell antigen commonly used in flow cytometry to count B lymphocytes?
CD19 is expressed from early B-cell development until the plasma-cell stage. CD2 and CD7 are T-cell markers; CD33 is a myeloid marker.
MHC class I molecules present peptide antigens to which cells?
MHC class I, found on all nucleated cells, presents intracellular (endogenous) peptides to CD8+ cytotoxic T cells. MHC class II presents exogenous peptides to CD4+ T cells.
Human HLA genes are located on which chromosome?
The major histocompatibility complex is on the short arm of chromosome 6. Beta-2 microglobulin, the light chain of class I molecules, is encoded on chromosome 15.