Topic 6 - The Immune System Flashcards
The monocytes of the blood are the precursors of tissue macrophages.
True
Neutrophils are only able to destroy bacteria circulating in the blood.
False
Neutrophils pass from the circulation into the tissues in response to chemotactic stimuli. Once in the tissues, they phagocytose and kill invading micro-organisms.
Complement facilitates the uptake of bacteria by phagocytes.
True
Macrophages use nitrous oxide to kill bacteria they have engulfed.
False
Macrophages use nitric oxide (and reactive oxygen intermediates)to kill organisms that they have ingested.
Natural killer cells act by destroying cells infected with a virus.
True
The lymphocytes are the most abundant white cells of the blood.
False
The neutrophils are the most abundant of the white cells (about 70 per cent). Lymphocytes account for about 25 per cent of the white cells of the blood.
Lymphocytes only leave the blood at sites of inflammation.
False
Lymphocytes leave the circulation to migrate through the tissues, finally re-entering the blood via the thoracic duct.
B lymphocytes mature in the bone marrow.
True
B lymphocytes respond to antigens in the extracellular fluid.
True
All B lymphocytes become plasma cells after they have been stimulated.
False
Although some B cells become transformed into plasma cells and secrete antibody, others remain in the lymphoid tissue as memory cells.
B lymphocytes secrete IgG when they are activated.
True
T cells respond to cells infected with a virus.
False
T cells respond to MHC molecules that incorporate a foreign peptide.
T lymphocytes mature in the thyroid gland.
True
T lymphocytes are derived from stem cells in the bone marrow and mature in the thymus gland.
All T cells secrete cytotoxic materials.
False
T cells are of two main kinds: helper cells and cytotoxic cells. Only the cytotoxic cells secrete cytotoxic materials to kill target cells. Helper cells secrete cytokines.
T cells respond to proteins on the host cells.
True
