The most abundant class of antibodies produced during a primary immune response is

Correct Answer: A

Rationale: The correct answer is A: IgM. During a primary immune response, IgM antibodies are the first class produced by plasma cells. IgM is the largest antibody and is effective at agglutinating pathogens. It is later followed by IgG production. IgE is involved in allergic reactions and parasitic infections, not typically produced in large amounts during a primary response. IgA is more abundant in mucosal tissues and secretions.

Correct Answer: C

Rationale: The correct answer is C because rods and cones in the human retina convert light energy into electrical signals through phototransduction, which are then sent as action potentials to the brain via the optic nerve. This process allows for visual information to be transmitted and processed by the brain. Choice A is incorrect as it refers to the conversion of light energy to chemical energy, which is not the primary function of rods and cones. Choice B is incorrect as rods and cones do not specifically absorb ultraviolet light. Choice D is incorrect as rods and cones do not absorb infrared light.

Correct Answer: D

Rationale: The correct answer is D: Diabetes. Anemia is a condition characterized by a lack of healthy red blood cells or hemoglobin. Diabetes does not directly cause anemia; it is a metabolic disorder affecting blood sugar levels. Iron deficiency anemia (A) is caused by a lack of iron, sickle cell anemia (B) is a genetic disorder affecting red blood cells, and aplastic anemia (C) is a bone marrow disorder. Therefore, the other choices are types of anemia, while diabetes is not.

Correct Answer: A

Rationale: The correct answer is A: Ilya Metchnikoff. He discovered phagocytes through his research on immune responses in starfish larvae. Metchnikoff observed cells engulfing foreign particles, leading to the discovery of phagocytosis. Louis Pasteur is famous for his work in microbiology and vaccination. Emil von Behring discovered antitoxins. Robert Koch is known for his work in bacteriology and identifying the causative agents of diseases. Therefore, the correct answer is A as Metchnikoff specifically discovered phagocytes.

Correct Answer: D

Rationale: The correct answer is D because CD14 is a glycosylphosphatidylinositol (GPI)-anchored protein expressed on the cell membrane that binds to LPS and facilitates its delivery to the TLR-4/MD-2 complex for recognition. CD14 does not transport TLR-4 (Choice A), bind LPS internally (Choice B), or act as an adaptor in the signaling pathway (Choice C). The key role of CD14 is to shuttle LPS to TLR-4/MD-2, initiating the immune response.