Choose the best definition for effector T cells. They are cells that

Correct Answer: D

Rationale: Effector T cells are fully activated, expanded, and capable of carrying out their functions, such as killing infected cells or assisting in immune responses. The correct choice (D) accurately describes the characteristics of effector T cells. They are not naïve cells (A), as they have encountered their specific antigen. They are not just starting to proliferate (B), as they have already undergone extensive proliferation. They have not only been energized (C), but have also completed the necessary steps for full activation and functionality.

Correct Answer: B

Rationale: Step 1: The current Influenza vaccine is designed to provide protection against multiple strains to increase effectiveness. Step 2: Option B includes a combination of different strains (H1N1, H5N1, and B), covering a broader spectrum of the virus. Step 3: Including different strains helps to address potential mutations and variations in circulating viruses. Step 4: Option B is the most comprehensive choice compared to others, offering a more robust protection against various strains. Summary: Option A is too limited with only 3 type A strains, while option C focuses only on 2009 H1N1 strain. Option D is also limited to only the most common seasonal H1N1 strain. Option B stands out as the correct choice for its broad coverage of different strains.

Correct Answer: C

Rationale: The correct answer is C: A strain of E. coli. "Hamburger disease" is commonly caused by E. coli O157:H7, a strain of Escherichia coli bacteria found in undercooked ground beef. This strain can lead to severe foodborne illness. Helicobacter pylori (Choice A) is associated with stomach ulcers, not hamburger disease. Salmonella typhimurium (Choice B) and Shigella flexneri (Choice D) are both known to cause food poisoning, but they are not typically linked to hamburger disease specifically. In this case, the unique association between E. coli O157:H7 and undercooked ground beef makes Choice C the correct answer.

Correct Answer: C

Rationale: Louis Pasteur's main contribution to immunology is the germ theory of disease and vaccine development. Firstly, Pasteur's germ theory revolutionized our understanding of infectious diseases by demonstrating that microorganisms are the cause. Secondly, he developed the concept of vaccination by creating vaccines for diseases such as rabies and anthrax, laying the foundation for modern immunology. The other choices are incorrect because: A: Pasteur worked on the rabies vaccine, not the smallpox vaccine. B: Phagocytosis was discovered by Metchnikoff, not Pasteur. D: Pasteur did not propose the theory of innate immunity.

Correct Answer: C

Rationale: Paul Ehrlich introduced the concept of discrimination between self and non-self through his "horror autotoxicus" theory. He proposed that the immune system can differentiate between harmful non-self antigens and self-antigens. Ehrlich's theory laid the foundation for understanding immune responses and the development of immunology. Metchnikoff focused on phagocytosis, Pasteur on microbiology, and Janeway on innate immunity, not specifically on self vs. non-self discrimination.