TB skin test is called 'Scatch test or Mantoux test' in which Tuberculin Purified Protein Derivative (PPD) is injected subcutaneously. This test is based on

Correct Answer: A

Rationale: The correct answer is A: Delayed Hypersensitivity. The TB skin test, also known as the Mantoux test, is based on the principle of delayed hypersensitivity reaction. When Tuberculin Purified Protein Derivative (PPD) is injected subcutaneously, in individuals previously exposed to TB, the immune system mounts a delayed hypersensitivity reaction resulting in localized inflammation at the injection site. This reaction is mediated by T cells and is indicative of previous exposure to the TB bacterium. Incorrect choices: B: Production of antibodies - The TB skin test does not detect the production of antibodies specific to TB, but rather the cellular immune response. C: Production of Tubercle toxin - The test is not based on the production of the tubercle toxin, but on the immune response to the tuberculin PPD. D: All these - While the immune response may involve various components, such as antibodies and cellular responses, the primary basis of the TB skin test is the

Correct Answer: B

Rationale: The correct answer is B: Perfusion. Pulmonary hypertension affects blood flow through the lungs, leading to decreased perfusion. This results in inadequate oxygenation of the blood. Acid-base balance (A) is maintained by the kidneys and lungs, not directly impacted by pulmonary hypertension. Diffusion (C) refers to gas exchange in the alveoli, which is affected by perfusion but not the primary disturbance in pulmonary hypertension. Ventilation (D) is the process of moving air in and out of the lungs, which is not primarily affected by pulmonary hypertension; it is more related to conditions like COPD.

Correct Answer: A

Rationale: The correct answer is A because a sensitized B cell requires activation by a helper T cell releasing cytokines to undergo differentiation and proliferation into plasma cells. This interaction is crucial for initiating the humoral immune response. Choices B, C, and D are incorrect because binding to a cytotoxic T cell, cloning of memory B cells, or cloning of plasma cells do not directly activate a sensitized B cell for its function in producing antibodies.

Correct Answer: B

Rationale: The correct answer is B (45 mm Hg) because the partial pressure of carbon dioxide in venous blood is typically around 40-45 mm Hg. This value represents the amount of CO2 dissolved in the blood plasma. Option A (40 mm Hg) is slightly on the lower side and may not fully reflect the average value. Option C (50 mm Hg) is higher than the usual range for venous blood CO2 levels. Option D (70 mm Hg) is significantly higher than the normal range and is more characteristic of arterial blood CO2 levels. Therefore, option B is the most accurate representation of the partial pressure of CO2 in venous blood.

Correct Answer: C

Rationale: The correct answer is C: electrolyte balance. Hemoglobin's affinity for oxygen is primarily influenced by factors such as pH, temperature, and the partial pressure of oxygen (PO2). Electrolyte balance, on the other hand, does not directly impact hemoglobin's ability to bind with oxygen. Changes in electrolyte levels may affect overall blood composition but do not directly alter hemoglobin's oxygen-binding capacity. Therefore, electrolyte balance does not affect hemoglobin's affinity for oxygen, making it the correct choice. RBC metabolic activity can impact oxygen release from hemoglobin, temperature can affect hemoglobin's oxygen-binding capacity, and the PO2 of blood directly influences oxygen binding to hemoglobin.