Some lymphocytes can survive as long as ______
weeks
days
decades
months
years
The Correct Answer is C
A. Weeks: While some activated lymphocytes may only survive for a few weeks after an immune response, memory lymphocytes are designed to persist much longer to provide lasting immunity.
B. Days: Effector lymphocytes, such as short-lived plasma cells, may function for days during an active immune response. However, this does not reflect the longevity of memory lymphocytes.
C. Decades: Memory lymphocytes, particularly memory T and B cells, can survive for decades. This long lifespan allows the immune system to “remember” pathogens encountered earlier in life and respond more rapidly upon re-exposure.
D. Months: Some lymphocytes can survive for months, but this is still short compared to memory cells that provide long-term immunity over decades.
E. Years: While memory lymphocytes can survive for many years, the most accurate term emphasizing their extreme longevity is decades, capturing their ability to persist through much of a person’s lifetime.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
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.
Correct Answer is E
Explanation
A. Heart:The heart is the central pump of the circulatory system, responsible for moving blood through the vessels. While critical, it alone does not constitute the complete circulatory system.
B. Blood vessels:Blood vessels provide the network of arteries, veins, and capillaries through which blood flows. However, without the heart to pump blood and the blood itself to carry gases and nutrients, vessels alone cannot sustain circulation.
C. Blood:Blood transports oxygen, nutrients, hormones, and waste products. While essential, blood cannot circulate on its own without a pump and vessels to guide its flow.
D. Heart and blood vessels:The combination of heart and vessels creates the structural framework for circulation, but the system is incomplete without blood, which carries the substances necessary to sustain life.
E. Heart, blood vessels, and blood:The circulatory system consists of the heart (pump), blood vessels (conduits), and blood (transport medium). All three components work together to deliver oxygen, nutrients, and hormones to tissues and remove wastes, making this the complete and correct answer.
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