During the adaptive immune response mature dendritic cells provide polarizing cytokines that influence the differentiation of Th subsets. The polarizing cytokine(s) produced by a dendritic cell depends on:

Correct Answer: B

Rationale: The correct answer is B: The type of pathogen it encounters. Dendritic cells produce different polarizing cytokines based on the type of pathogen they encounter. This is crucial for directing the differentiation of T helper (Th) subsets. Choice A is incorrect because the expression of MHC class I or II molecules by dendritic cells is important for antigen presentation to T cells, not for determining polarizing cytokines. Choice C is also incorrect because Fc receptors are involved in antibody-mediated immune responses, not in determining polarizing cytokines. Therefore, the correct answer is B as it directly influences the differentiation of Th subsets by providing appropriate polarizing cytokines based on the encountered pathogen.

Correct Answer: D

Rationale: The correct answer is D: Artificial passive. Plasma therapy involves administering preformed antibodies to provide immediate protection against a specific pathogen. This is considered artificial passive immunity because the antibodies are obtained from an external source rather than being produced by the individual's immune system. Explanation: 1. Natural active immunity (Choice A) is when the body produces its antibodies after exposure to a pathogen, which is not the case in plasma therapy. 2. Natural passive immunity (Choice B) is when antibodies are passed from mother to fetus or through breast milk, not obtained through plasma therapy. 3. Artificial active immunity (Choice C) involves vaccination to stimulate the body's immune response, which is different from plasma therapy. In summary, the correct answer is D (Artificial passive) because plasma therapy provides immediate immunity through externally sourced antibodies, distinguishing it from the other types of immunological protection.

Correct Answer: C

Rationale: The correct answer is C: 1-b, 2-d, 3-a, 4-c. 1. The first match should be b, as it aligns with the order given. 2. The second match should be d, as it aligns with the order given. 3. The third match should be a, as it aligns with the order given. 4. The fourth match should be c, as it aligns with the order given. Therefore, option C is the correct match based on the given order. Other choices are incorrect because they do not align with the given order of matches.

Correct Answer: B

Rationale: The correct answer is B: Passive natural immunity occurs. This type of immunity is achieved through the transfer of antibodies (IgG) from the mother to the fetus during pregnancy. The antibodies provide protection to the newborn for the first few months of life. It is considered passive because the newborn is not actively producing the antibodies themselves. A: Active natural immunity occurs when the body produces its antibodies in response to exposure to an antigen. This is not the case for newborns receiving maternal IgG. C: Active artificial immunity occurs when the body is intentionally exposed to an antigen, such as through vaccination, to stimulate an immune response. This is not relevant to the scenario described. D: Passive artificial immunity occurs when pre-formed antibodies are transferred to an individual through a medical intervention, such as receiving immune globulin. This is not applicable to the situation of maternal transmission of IgG to newborns.

Correct Answer: B

Rationale: The correct answer is B: mycoplasmas. Mycoplasmas have cell walls, which contain peptidoglycan, making them structurally similar to typical bacteria. Algae (choice A) have cell walls made of cellulose, Gram-positive bacteria (choice C) have cell walls containing thick layers of peptidoglycan, and fungi (choice D) have cell walls made of chitin. Mycoplasmas lack a cell wall, but they have a flexible cell membrane that provides them with shape and protection.