Which of the following statements is FALSE regarding B cells?

Correct Answer: B

Rationale: B cells develop in the bone marrow, not the thymus. Firstly, hematopoietic stem cells in the bone marrow give rise to B cells. They undergo maturation and selection processes in the bone marrow, not in the thymus. Therefore, choice B is false. On the other hand, choices A, C, and D are correct. A is true because B cells with high affinity to self-antigens undergo apoptosis to prevent autoimmunity. C is true since B cells synthesize antibodies which can be displayed on their surface as B cell receptors. D is true because B cells can undergo class switching to produce different types of antibodies based on the immune response requirements.

Correct Answer: A

Rationale: The correct answer is A: TRUE. The innate immune system is the body's first line of defense against infections and is always active, providing immediate protection without prior exposure to a specific pathogen. It includes physical barriers, such as skin and mucous membranes, and cellular components like phagocytes and natural killer cells. The innate immune response is nonspecific and rapid, providing a crucial initial defense against pathogens. Choice B is incorrect because the innate immune system is always active, even without any prior exposure to pathogens. Choice C is incorrect because the innate immune system is consistently functioning to protect the body, regardless of the situation. Choice D is incorrect as the correct answer is A.

Correct Answer: B

Rationale: The correct answer is B: Macrolides. Listeriosis is typically treated with antibiotics such as Penicillin and ampicillin due to their effectiveness against Listeria monocytogenes. Macrolides, on the other hand, are not first-line agents for listeriosis treatment. They are less effective in treating this bacterial infection compared to Penicillin and ampicillin. Cephalosporins may also be less effective against Listeria monocytogenes compared to Penicillin and ampicillin. Choice D is incorrect as Macrolides are not suitable for listeriosis treatment.

Correct Answer: D

Rationale: The correct answer is D: All of these. HBV, HCV, and HDV can all lead to chronic carrier states due to their ability to establish persistent infections in the liver. HBV can result in chronic hepatitis, cirrhosis, and even liver cancer. HCV can also lead to chronic hepatitis and liver damage. HDV is a defective virus that requires HBV for replication and can worsen the outcome of HBV infection, potentially leading to chronic liver disease. Therefore, all three viruses have the potential to cause chronic carrier states.

Correct Answer: A

Rationale: The correct answer is A: IgG. IgG is the most abundant class of immunoglobulins in the body, constituting about 75% of total immunoglobulins. IgG plays a crucial role in long-term immunity, neutralizing toxins, and enhancing phagocytosis. IgE is involved in allergic reactions, IgD is mainly found on B cells and functions as a receptor, and IgM is the first antibody produced in response to an infection but is less abundant compared to IgG. Therefore, IgG is the correct choice based on its abundance and diverse functions in the immune system.