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 B
Explanation
Epinephrine, also known as adrenaline, is a hormone that the adrenal medulla secretes in response to stress or low blood sugar levels.
It helps the body react to stress by increasing blood pressure, heart rate, oxygen delivery to muscles, and blood sugar levels.
Choice A is wrong because mineralocorticoids are hormones that the adrenal cortex secretes, not the adrenal medulla.
They help regulate the balance of sodium and potassium in the body.
Choice C is wrong because glucocorticoids are also hormones that the adrenal cortex secretes, not the adrenal medulla.
They help control the body’s use of fats, proteins, and carbohydrates, suppress inflammation, and regulate blood pressure and blood sugar.
Choice D is wrong because aldosterone is a specific type of mineralocorticoid that the adrenal cortex secretes, not the adrenal medulla.
It helps regulate the balance of sodium and water in the body.
Correct Answer is A
Explanation
The correct answer is choice A. True.
Blood flow through a capillary is controlled by a precapillary sphincter, which opens or closes due to the requirements of the cells supplied by the capillary.
This allows blood to bypass the capillaries when they are not needed and to increase blood flow when they are needed.
Choice B. False is wrong because it contradicts the true statement in choice A. A precapillary sphincter is a ring of smooth muscle that surrounds the entrance of a capillary and regulates blood flow into it.
It is influenced by local factors such as oxygen, carbon dioxide, pH, and temperature.
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