One group of proteolytic enzymes secreted by natural killer (NK) cells is _______
granzymes
selectins
cytokines
Interferons
perforins
The Correct Answer is A
A. Granzymes: Granzymes are proteolytic enzymes released by NK cells into target cells after perforin creates entry pores. They trigger apoptosis by activating caspases and degrading intracellular components, allowing NK cells to eliminate virus-infected or cancerous cells efficiently.
B. Selectins: Selectins are adhesion molecules that help leukocytes migrate during inflammation. They are not enzymes and are not secreted by NK cells, as their role involves cell-to-cell binding rather than inducing apoptosis.
C. Cytokines: Cytokines are signaling molecules used for communication within the immune system. Although NK cells secrete cytokines like IFN-γ, cytokines are not proteolytic enzymes and do not directly induce programmed cell death.
D. Interferons: Interferons are antiviral signaling proteins that enhance immune defense, but they are not proteolytic and do not mediate direct killing. NK cells may secrete interferons, yet these are regulatory rather than destructive molecules.
E. Perforins: Perforins create pores in the target cell membrane, enabling granzymes to enter. While essential to NK-cell function, perforins themselves are not proteolytic enzymes, but rather pore-forming proteins.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. The location of the target cells in the body:While the anatomical location of cells determines which tissues are exposed to circulating hormones, responsiveness is not dictated by location alone. Only cells with the appropriate receptors will respond.
B. The location of the gland that secretes the hormone:The position of the endocrine gland affects hormone distribution through the bloodstream but does not determine whether a cell is responsive. Responsiveness depends on receptor expression on the target cell.
C. The presence of a receptor for that particular hormone:A cell is responsive to a hormone only if it has specific receptors for that hormone. The binding of the hormone to its receptor triggers intracellular signaling pathways, leading to a physiological response.
D. The chemical properties of the hormone:The chemical nature of a hormone (e.g., peptide or steroid) affects how it interacts with receptors and enters cells, but it does not determine whether a cell is responsive; receptor presence is the key factor.
E. The site where the hormone is secreted:The secretion site influences how quickly the hormone reaches target cells, but a cell cannot respond without the appropriate receptor, making the secretion site irrelevant for responsiveness.
Correct Answer is C
Explanation
A. Spleen:The spleen is involved in filtering blood and recycling old red blood cells, and it houses some immune cells, but it is not the primary site of hemopoietic stem cells in adults.
B. Yellow bone marrow:Yellow bone marrow primarily consists of adipose tissue and has limited hemopoietic activity under normal conditions; it can revert to red marrow during severe blood loss.
C. Red bone marrow:Red bone marrow is the main site of hemopoietic stem cells in adults. These stem cells differentiate into all blood cell types-erythrocytes, leukocytes, and platelets-supporting continuous blood formation.
D. Thymus:The thymus is a primary lymphoid organ responsible for T-lymphocyte maturation, not for general hemopoiesis or stem cell storage.
E. Liver:In fetal development, the liver is an important site of hemopoiesis, but in adults, it no longer functions as a primary source of hemopoietic stem cells.
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