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 D
Explanation
Atrial natriuretic peptide (ANP) is a hormone secreted by the heart when the atria are stretched by high blood pressure or volume.
ANP has multiple effects, such as increasing urine and salt excretion, lowering blood pressure, and opposing the renin-angiotensin-aldosterone system.
Therefore, ANP inhibits the release of renin and aldosterone, which are hormones that increase blood pressure and sodium retention.
Choice A is wrong because ANP is not released from the adrenal cortex but from the cardiac atria.
ANP does not stimulate atrial hormones but rather inhibits them.
Choice B is wrong because ANP is not stimulated to release when blood volume decreases, but when it increases.
ANP acts to reduce blood volume by promoting diuresis and natriuresis.
Choice C is wrong because ANP does not raise blood pressure, but lowers it. ANP acts as a vasodilator and reduces peripheral resistance.
Correct Answer is B
Explanation
The correct answer is choice B. True.
As a result of the allergen-antibody reaction, mast cells release histamine.
This is because when mast cells are exposed to an allergen that binds to IgE antibodies attached to their FcɛRI receptors, they release histamine and other inflammatory mediators.
Histamine causes vasodilation, increased capillary permeability, mucus secretion, and smooth muscle contraction, which result in allergic symptoms such as itching, swelling, sneezing, and wheezing.
Choice A is wrong because it is the opposite of the correct answer.
Mast cells do release histamine in response to allergen-antibody reactions. Some additional sentences are:
Normal ranges of histamine levels vary depending on the tissue and the method of measurement, but they are usually low in healthy individuals and elevated in allergic conditions.
Histamine can be degraded by enzymes such as diamine oxidase and histamine N-methyltransferase, or inhibited by drugs such as antihistamines.
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