Which of the following cells are 'professional' antigen presenting cells

Correct Answer: C

Rationale: The correct answer is C: Macrophages, B cells, dendritic cells. Professional antigen-presenting cells are specialized immune cells that effectively present antigens to T cells. Macrophages, B cells, and dendritic cells are considered professional APCs because they express major histocompatibility complex (MHC) molecules and co-stimulatory molecules, allowing them to effectively activate T cells. Neutrophils and epithelial cells are not considered professional APCs as they have limited ability to present antigens to T cells. B cells and T cells are not APCs themselves, but B cells can act as APCs when they present antigens to T cells in the context of an immune response.

Correct Answer: D

Rationale: The correct answer is D because it is the only statement that is not entirely true regarding the microbiota. The rationale for this is that bacteria found in obese mice are actually more efficient at extracting energy from food, not less efficient as mentioned in option D. This increased efficiency contributes to the higher energy extraction from food, leading to weight gain in obese individuals. The other options (A, B, C) are correct as they align with current research and understanding of the microbiota. Option A is true as the microbiota begins to colonize our body at birth. Option B is also true as the composition of the microbiota in adults can indeed be influenced by various factors such as diet and exercise. Option C is true as obesity has been linked to alterations in gut microbiota composition, and studies have shown that transferring microbiota from obese to lean mice can induce weight gain in the lean mice.

Correct Answer: C

Rationale: The correct answer is C: Peptidoglycan. NOD1 recognizes peptidoglycan, a component of bacterial cell walls. This recognition triggers an immune response. Flagellin (A) is recognized by TLR5, CpG DNA (B) is recognized by TLR9, and K+ efflux (D) is not a PAMP recognized by NOD1. Thus, only peptidoglycan is the correct choice for NOD1 recognition.

Correct Answer: C

Rationale: The correct answer is C because the C3 convertase is an enzyme that cleaves C3 into C3a and C3b, an essential step in the complement cascade. This enzyme is crucial for the initiation of both the classical and alternative pathways. Choice A is incorrect as opsonins enhance phagocytosis but are not directly related to C3 convertase. Choice B is incorrect as the MAC is formed by the terminal complement components, not the C3 convertase. Choice D is incorrect as C3b is not an inhibitor but a product of C3 cleavage by the C3 convertase.

Correct Answer: A

Rationale: The correct answer is A because innate behaviors are indeed under strong genetic control. These behaviors are instinctual and are genetically programmed in organisms. This genetic control ensures that all individuals of a species exhibit these behaviors consistently. Choice B is incorrect because while innate behaviors may be performed similarly by individuals of a species, there can still be variations. Choice C, Sociobiology, is incorrect as it is a branch of biology that studies social behavior in animals. Choice D, the environment, is incorrect as innate behaviors are not primarily influenced by the environment but rather by genetic factors.