Which of the following is NOT true about live attenuated vaccines

Correct Answer: D

Rationale: The correct answer is D: Able to induce only a humoral response. Live attenuated vaccines can induce both humoral and cellular immune responses, not just humoral. This is because they mimic natural infection, leading to a broader immune response. A: Usually effective at a single dose - This is true for live attenuated vaccines, as they often provide long-lasting immunity with just one dose. B: Expensive handling and storage - Live attenuated vaccines can be more cost-effective due to fewer doses needed, not expensive. C: Potential hazard due to reversion to a virulent form - This is a concern with live attenuated vaccines, as there is a risk of the weakened virus reverting to a virulent form.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: A

Rationale: The correct answer is A: Passage through cultured cells. Attenuated vaccines are produced by weakening the pathogen through serial passages in cultured cells, reducing virulence while maintaining immunogenicity. Formaldehyde treatment (B) disrupts the pathogen's structure and is used for inactivated vaccines. The use of viral vectors carrying pathogen subunits (C) is a method for creating subunit vaccines, not attenuated vaccines. Therefore, D is incorrect as not all treatments lead to attenuated vaccines.

Correct Answer: B

Rationale: The correct answer is B: IgG. IgG plays a major role in opsonization by binding to antigens and marking them for phagocytosis. IgM is the first antibody produced in response to an infection but is not as effective in opsonization. IgA primarily protects mucosal surfaces. IgD is involved in the activation of B cells, not opsonization. In summary, IgG is the correct choice due to its specific role in opsonization compared to the other isotypes.

Correct Answer: D

Rationale: The correct answer is D because T cell development starts in the thymus while the naïve T cell activation by antigen occurs outside of the thymus. T cell development involves positive and negative selection, establishing MHC restriction, and interaction with thymic dendritic cells for maturation. Naïve T cells are activated by antigens in the periphery, not during T cell development in the thymus. Therefore, D is the correct answer as it does not align with the process of T cell development.