Which of the following is considered a defining characteristic of a TH2 response?

Correct Answer: D

Rationale: The correct answer is D: Production of IgE antibodies. A TH2 response is characterized by the production of IgE antibodies, which are essential in allergic reactions. IgM antibodies (A) are produced during the primary immune response. Activation of CTL (B) is associated with a TH1 response. Neutrophils (C) are primarily involved in the innate immune response and are not specific to TH2 responses. In summary, the production of IgE antibodies is a defining characteristic of a TH2 response, distinguishing it from other immune responses.

Correct Answer: C

Rationale: The correct answer is C, transfer of serum from someone who has survived an infection with Pathogen X. This provides passive immunity through the transfer of antibodies from the immune individual to the recipient, offering immediate protection. Choice A involves active immunity through vaccination, which requires the individual's immune response to produce antibodies. Choice B involves active infection, not passive immunity. Choice D mentions living amongst immunized individuals, which may confer herd immunity but does not provide passive immunity on an individual level.

Correct Answer: A

Rationale: The correct answer is A: Natural Killer (NK) cells. NK cells are involved in antibody-dependent cell-mediated cytotoxicity by recognizing target cells coated with antibodies and inducing their death. NK cells play a crucial role in immune surveillance and defense against infected or malignant cells. Neutrophils, macrophages, and mast cells are not directly involved in antibody-dependent cell-mediated cytotoxicity. Neutrophils are primarily responsible for phagocytosis, macrophages are antigen-presenting cells, and mast cells are involved in allergic reactions.

Correct Answer: C

Rationale: The correct answer is C: Phagocytosis. Phagocytosis is a fundamental process that emerged early in evolution for cellular organisms to engulf and digest particles. This process is essential for basic survival and defense mechanisms. A: Antigen presentation and B: Antibody production are more advanced immune responses that occur in higher organisms and require a complex immune system. D: Thymic education is a process specific to vertebrates involving the maturation and selection of T cells, which is a more evolved mechanism compared to phagocytosis. Therefore, phagocytosis is the earliest process among the options listed as it is essential for basic cellular survival and predates the development of advanced immune responses.

Correct Answer: A

Rationale: The correct answer is A. Smack is a street name for heroin, which is derived from the latex of Papaver somniferum, commonly known as the opium poppy. The latex of this plant contains morphine and codeine, which are the main components of heroin. Cannabis sativa (B) refers to marijuana, not smack. Dhatura (C) and Erythroxylum coca (D) are sources of other drugs like scopolamine and cocaine, respectively, not heroin. Therefore, A is the correct answer as it corresponds to the actual source of smack/heroin.