Triggers for complement activation include

Correct Answer: D

Rationale: The correct answer is D because all three choices are valid triggers for complement activation. A is correct as opsonins like MBL can bind to microbes and activate the complement system. B is correct as direct recognition of microbes can also trigger complement activation. C is correct as the formation of immune complexes can lead to complement activation through the classical pathway. Therefore, all of the above choices are triggers for complement activation.

Correct Answer: D

Rationale: The correct answer is D because a heart attack, also known as a myocardial infarction, involves damage to the cardiac muscle due to a blocked coronary artery. Choice A is correct as it directly relates to the definition of a heart attack. Choice B is also correct as a blocked coronary artery is the main cause of decreased blood flow to the heart muscle leading to a heart attack. Choice C is incorrect as it refers to a stroke, which is the death of brain tissue due to blocked arteries in the head, not a heart attack. Therefore, A & B (choices A and B) are the correct options, making D the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Producing hormones. The immune system's main functions are to protect the body from foreign substances and repair damaged tissues. Producing hormones is not a direct function of the immune system. Hormone production is primarily regulated by the endocrine system, not the immune system. Therefore, option B is not a function of the immune system. Options A and C are incorrect as protecting the body from foreign substances and repairing damaged tissues are essential roles of the immune system. Option D is incorrect because not all functions listed are actually performed by the immune system.

Correct Answer: C

Rationale: The correct answer is C: Aplastic anemia. Aplastic anemia is a condition where the bone marrow doesn't produce enough blood cells, including red blood cells. Iron deficiency anemia (A) is caused by a lack of iron in the body, not a deficiency in red blood cell production. Sickle cell anemia (B) is a genetic disorder affecting the shape of red blood cells, not the production. Pernicious anemia (D) is caused by a lack of vitamin B12, which leads to a deficiency in red blood cell production, but it is not the medical term specifically used for this condition.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Lysozyme is an enzyme that destroys bacterial cell walls. 2. This action acts as a preformed chemical barrier against pathogens. 3. Mucus (choice A) is a physical barrier, not a preformed chemical one. 4. Tight junctions (choice C) and cilia (choice D) are structural components, not chemical barriers. Summary: - Choice B, Lysozyme, is correct as it actively targets and destroys pathogens. - Choices A, C, and D are incorrect as they do not directly function as preformed chemical barriers.