Which of the following is NOT an outcome of complement activation:

Correct Answer: D

Rationale: The correct answer is D: Increased migration of dendritic cells from tissues to lymph nodes. Complement activation does not directly lead to the migration of dendritic cells. Complement activation can lead to increased recruitment of inflammatory cells (A), opsonization of pathogens (B), and lysis of pathogens (C). Dendritic cells typically migrate to lymph nodes to present antigens to T cells, but this process is not directly mediated by complement activation.

Correct Answer: C

Rationale: The correct answer is C because immunoglobulin gene rearrangement creates a complete V exon in the B cell DNA. This process happens during B cell development, where segments of V, D, and J gene regions are rearranged to form a functional immunoglobulin gene. This rearrangement occurs before transcription, so option A is incorrect. Option B is incorrect because the V exon is not complete in the germline DNA, but rather created through rearrangement in the B cell DNA. Option D is incorrect as it combines two incorrect statements.

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 the adaptive immune response relies on the initiation by the innate immune response (A), involves both humoral (antibody production) and cell-mediated (T cell activation) responses (B), and produces cytokines that can modulate the activity of innate immune cells like macrophages (C). Therefore, all of the statements are true regarding the adaptive immune response, making option D the correct choice.

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.