MLT GlobeImmunology & Serology: Immune system principles – page 3
257 Immunology & Serology MCQs on Immune system principles with answers and explanations.
Which feature describes innate immunity?
Innate defences are present from birth and act immediately. Memory and antigen specificity are features of adaptive immunity.
The first physical barrier against invading microbes is the:
Intact skin and mucous membranes are the first line of innate defence.
Normal flora protect against pathogens mainly by:
Commensals block pathogens by competing for nutrients and attachment sites and by making bacteriocins and acids. Antibodies are made by the host.
Which gastric factor kills most swallowed microorganisms?
Low pH from HCl destroys most ingested microbes. Hyaluronidase and haemolysin are bacterial virulence factors.
Which is NOT a function of complement?
Complement opsonizes (C3b), lyses (MAC) and promotes inflammation (C3a, C5a); antibodies are made by plasma cells.
Interferon-alpha and -beta are proteins released mainly by:
Type I interferons are released by virus-infected cells and induce an antiviral state in neighbouring cells.
Which is NOT part of innate defence?
Memory B-cell antibody responses are adaptive. Skin, interferons and phagocytes are innate.
Which blood cell is a professional phagocyte?
Neutrophils ingest and kill bacteria. NK cells kill by cytotoxicity and plasma cells secrete antibody.
Phagocytes destroy ingested microbes mainly through:
Lysosomes fuse with phagosomes, delivering enzymes and reactive oxygen species that destroy microbes.
Which cell uses reactive oxygen species and lysozyme to kill ingested pathogens?
Macrophages kill phagocytosed microbes via oxidative burst and lysosomal enzymes. NK and T cells kill other cells by perforin and granzymes.
Redness, heat, swelling and pain after tissue injury form a response called:
Inflammation involves vasodilation, increased permeability and leukocyte recruitment. Phagocytosis is one part of it.
Which cytokine is a classic endogenous pyrogen?
IL-1, with IL-6 and TNF, acts on the hypothalamus to cause fever. IL-2 promotes T-cell growth and IL-10 is anti-inflammatory.
Toll-like receptors are:
TLRs on host cells recognize conserved microbial patterns such as LPS and trigger innate responses.
A small molecule that elicits antibody only when attached to a carrier protein is a(n):
Haptens are antigenic but not immunogenic alone. Adjuvants non-specifically enhance immune responses.
The part of an antigen that binds an antibody is the:
The epitope is the antigenic determinant; the paratope is on the antibody.
Which class of molecule is generally the most potent immunogen?
Large proteins are complex and T-dependent, so they are strongest immunogens.
Which cell is the most efficient antigen-presenting cell for naive T cells?
Dendritic cells capture and process antigen and present it to naive T cells in lymph nodes.
After migrating into tissue, a monocyte becomes a:
Monocytes enter tissues and mature into macrophages, e.g. Kupffer cells.
Which statement about IgM is correct?
Pentameric IgM is a strong complement activator. IgG dominates secondary responses and crosses the placenta.
Which statement about IgA is correct?
Secretory IgA is abundant in milk, tears and saliva. IgE triggers anaphylaxis.