Which of the following is a function of T-helper cells that is necessary for the development of an immune response?
Stimulates activation of B-cells
Provides the first line of defense against infection
Activates macrophages
Minimizes cell damage caused by T-cells
The Correct Answer is A
A. T-helper cells (CD4+ cells) play a crucial role in initiating and coordinating the immune response. They stimulate the activation of B-cells to produce antibodies and help activate cytotoxic T-cells to target infected cells.
B. The first line of defense against infection is provided by physical barriers like the skin, mucous membranes, and innate immune responses, not by T-helper cells.
C. While T-helper cells can activate macrophages indirectly by releasing cytokines, their primary role is in helping to activate other immune cells like B-cells and cytotoxic T-cells, rather than directly activating macrophages.
D. T-helper cells are not directly involved in minimizing cell damage caused by T-cells. That role is more closely related to regulatory T-cells (Tregs) that help maintain immune tolerance and prevent excessive immune responses.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. The atrioventricular (AV) valves separate the atria from the ventricles. The right AV valve is called the tricuspid valve, and the left AV valve is the mitral valve. These valves ensure that blood flows from the atria into the ventricles without flowing back. This is the correct answer.
B. The pulmonary valve is located between the right ventricle and the pulmonary artery. It does not separate the atria and ventricles.
C. The aortic valve separates the left ventricle from the aorta and prevents blood from flowing back into the ventricle after contraction. It does not separate the atrial and ventricular chambers.
D. The semilunar valves, which include the pulmonary and aortic valves, are located at the exit of the ventricles but do not separate the atria from the ventricles.
Correct Answer is D
Explanation
A. Flexion refers to a bending movement that decreases the angle between two body parts, such as bending the knee or elbow, but it does not involve lateral movement away from the body's midline.
B. Adduction is the movement of a body part toward the midline of the body, opposite of what the question describes.
C. Extension refers to a straightening movement that increases the angle between two body parts, such as straightening the arm or leg, but again does not involve lateral movement.
D. Abduction is the correct term for moving a limb or body part away from the midline of the body. In this case, it refers to the lateral movement of the leg away from the body's midline.
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