T lymphocytes are responsible for:
Humoral immunity.
Cell-mediated immunity.
Programming macrophages.
Producing antibodies.
The Correct Answer is B
T lymphocytes, also known as T cells, are a type of white blood cell that is an essential part of the immune system.
T cells are one of two primary types of lymphocytes — B cells being the second type — that determine the specificity of immune response to antigens (foreign substances) in the body.
T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface.
T cells originate in the bone marrow and mature in the thymus.
After migration to the thymus, the precursor cells mature into several distinct types of T cells.
One of these types is the CD8+ T cell, also known as cytotoxic T cell, which is responsible for cell-mediated immunity.
Cell-mediated immunity is the type of immunity that involves the direct killing of infected cells and cancer cells by cytotoxic T cells.
Choice A is wrong because humoral immunity is the type of immunity that involves the production of antibodies by B cells and plasma cells.
Antibodies are proteins that bind to specific antigens and mark them for destruction by other immune cells.
Choice C is wrong because programming macrophages is not a function of T lymphocytes.
Macrophages are a type of phagocytic cell that can engulf and digest pathogens and cellular debris.
Macrophages can be activated by cytokines, which are chemical messengers secreted by helper T cells and other immune cells.
Choice D is wrong because producing antibodies is not a function of T lymphocytes.
As mentioned above, antibodies are produced by B cells and plasma cells, which are another type of lymphocyte.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
The endocrine system may have a longer-lasting effect than the nervous system because the hormones it produces can circulate in the bloodstream for a long time and affect many organs and tissues.
The nervous system, on the other hand, uses nerve impulses and neurotransmitters for communication, which are faster but more short-lived.
Choice A is wrong because the endocrine system is essential to life.
It regulates many vital functions such as metabolism, growth, reproduction, mood, sleep, and blood pressure.
Choice B is wrong because the endocrine system takes longer than the nervous system to deliver its messages.
The hormones have to travel through the bloodstream to reach their target cells, while the nerve impulses can travel along the nerve fibers at high speeds.
Choice D is wrong because the endocrine system does use receptors.
The hormones bind to specific receptors on the target cells to trigger a response.
Correct Answer is A
Explanation
Capillary walls consist of a single layer of epithelial cells, and they exchange substances in the blood for substances in the tissue fluid surrounding body cells.
This single layer of cells is called the endothelium and it forms the barrier between the blood and the interstitial fluid.
The endothelium can be either continuous or fenestrated, depending on the tissue type and function.
The capillaries are very thin and allow red blood cells to flow through them single file.
The capillaries also have a layer of a glycoprotein called the glycocalyx that covers their luminal surface.
Choice B. False is wrong because it contradicts the definition and structure of capillaries.
Capillaries are not made of multiple layers of cells, nor do they prevent the exchange of substances between the blood and the tissue fluid.
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