Which of the following is not an antigen presenting cell?
Dendritic cell
B cell
Macrophage
all of the above are APCs
NK cell
The Correct Answer is E
A. Dendritic cell: Dendritic cells are professional antigen-presenting cells (APCs) that capture antigens, process them, and present them on MHC molecules to T lymphocytes, initiating adaptive immune responses.
B. B cell: B cells can function as APCs by internalizing antigens via their B cell receptor, processing them, and presenting antigen fragments on MHC II molecules to helper T cells.
C. Macrophage: Macrophages are APCs that engulf pathogens and present antigen fragments to T cells, linking innate and adaptive immunity.
D. All of the above are APCs: While dendritic cells, B cells, and macrophages are APCs, this statement is misleading because it ignores the presence of non-APCs like NK cells.
E. NK cell: Natural killer (NK) cells are not antigen-presenting cells. They are cytotoxic lymphocytes of the innate immune system that destroy virus-infected and tumor cells without presenting antigens to T cells.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Appendix:The appendix contains lymphoid tissue and participates in immune surveillance, but it does not serve as a site for T cell maturation. Its role is primarily secondary immune function rather than primary lymphocyte development.
B. Thymus:T lymphocytes migrate from the bone marrow to the thymus to mature and acquire immunocompetence. The thymus provides the specialized environment for T cell differentiation, selection, and education before they enter circulation.
C. Spleen:The spleen functions as a secondary lymphoid organ where T cells encounter antigens and mount immune responses, but it does not support initial T cell maturation.
D. Tonsils:Tonsils are secondary lymphoid structures that trap antigens and facilitate local immune responses. They do not serve as a site for T cell development or maturation.
Correct Answer is A
Explanation
A. Blood vessel diameter:Vessel diameter has the greatest influence on blood flow resistance because resistance is inversely proportional to the fourth power of the radius. Small changes in diameter, especially in arterioles, can dramatically increase or decrease resistance, making it the most significant factor.
B. Blood vessel type:While different types of vessels (arteries, arterioles, capillaries, veins) have structural differences, the type itself does not directly determine resistance as much as the diameter within those vessels.
C. Blood viscosity:Blood viscosity affects resistance, with thicker blood increasing friction. However, normal physiological variations in viscosity are relatively minor compared with the impact of changes in vessel diameter.
D. Total blood vessel length:Longer vessels contribute to higher resistance, but vessel length is generally constant in adults. Therefore, its effect on resistance is less significant than diameter, which can change dynamically through vasoconstriction or vasodilation.
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