A clinical indicator of inflammation is:

Correct Answer: B

Rationale: The correct answer is B: Increased concentration of C-reactive protein. This is because C-reactive protein is a well-established clinical indicator of inflammation, produced by the liver in response to inflammation. Choice A is incorrect because a decreased concentration of C3b is not a typical indicator of inflammation. Choice C is incorrect because mannose-binding lectin (MBL) is an acute-phase reactant that increases in response to inflammation, so a decreased concentration of MBL would not be indicative of inflammation. Choice D is incorrect as it includes all options, but only B is a valid clinical indicator of inflammation.

Correct Answer: A

Rationale: The correct answer is A. Virus typically triggers a Th1 response because Th1 cells are specialized in combating intracellular pathogens like viruses. Th2 response is more common for extracellular parasites, making choice B incorrect. TH17 response is usually associated with fungal infections and autoimmune diseases, making choice C incorrect. Parasitic worms usually induce a Th2 response due to their extracellular nature, making choice D incorrect.

Correct Answer: D

Rationale: The correct answer is D because the statement incorrectly implies that the bacterial type III secretion system is used by gut microbiota to invade intestinal epithelial cells in Crohn's disease. In reality, Crohn's disease is not directly caused by invasion of gut microbiota into intestinal cells; it is a complex autoimmune condition. The gut microbiota dysbiosis is associated with Crohn's disease, but invasion of epithelial cells is not the primary mechanism. Choices A, B, and C are correct: A highlights the altered microbiome in obesity, B discusses the use of fecal transplants for C. difficile infections, and C mentions Crohn's disease related to issues with gut microbiota tolerance.

Correct Answer: A

Rationale: Rationale for Choice A: Outbreaks of measles in developed countries are due to decreased vaccination rates, leading to lower herd immunity. This is supported by data showing increasing cases in countries with vaccine hesitancy. Other choices are incorrect because B is false - measles has not been eradicated globally, C is false - there is an effective vaccine for measles, and D is false - measles can lead to severe complications and long-term effects, especially in unvaccinated individuals.

Correct Answer: C

Rationale: The correct answer is C because the human microbiome does not secrete enzymes like lysozyme; instead, lysozyme is produced by the human body. A is correct as the microbiome can out-compete harmful bacteria. B is correct as the microbiome produces short chain fatty acids. D is correct as the microbiome helps in the development of the gut-associated immune system. Therefore, C is the only option that does not accurately describe a benefit from the human microbiome.