Which of the following is NOT true about a potential vaccine that induces a strong cytotoxic T cell response to influenza virus but failed to induce neutralizing antibodies:

Correct Answer: D

Rationale: The correct answer is D because a strong cytotoxic T cell response can still effectively clear the virus even without neutralizing antibodies. Cytotoxic T cells directly kill infected cells, helping to control and eliminate the virus. Therefore, the vaccine would not result in failure to clear the virus. A) Incorrect: While the vaccine may not prevent infection, the presence of cytotoxic T cells would help in controlling and reducing the severity of the infection. B) Incorrect: The vaccine may indeed lessen the severity of the disease by aiding in the clearance of infected cells. C) Incorrect: A strong T cell response can provide broader protection against different variants of the virus.

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: D

Rationale: Step 1: Adjuvants like AS03 induce danger signals by activating innate immunity, enhancing the response to the vaccine. Step 2: Adjuvants generally boost the innate immune response by increasing antigen presentation and cytokine production. Step 3: Adjuvants create a slower release of antigen, forming an antigen depot which prolongs immune stimulation. Summary: Choice D is correct because adjuvants like AS03 do induce danger signals, boost the innate immune response, and create a slower release of antigen, leading to enhanced vaccine efficacy. Choices A, B, and C are incorrect as they do not encompass all the effects of adjuvants in flu vaccines.

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.