Humoral factors of the natural resistance are:

Correct Answer: B

Rationale: The correct answer is B because lysozyme, lactoferrin, interferon, and complement are all humoral factors involved in natural resistance. Lysozyme and lactoferrin are antimicrobial proteins that help defend against pathogens. Interferon is a signaling protein that inhibits viral replication, while complement is a group of proteins that enhance the immune response by promoting inflammation and opsonization. Choices A, C, and D are incorrect: - Choice A mentions only macrophages, which are not humoral factors but rather phagocytic cells. - Choice C lists immune cells involved in adaptive immunity (B and T lymphocytes, NK cells) rather than humoral factors of natural resistance. - Choice D includes immunoglobulins, which are part of adaptive immunity, not natural resistance.

Correct Answer: A

Rationale: Rationale: A: Incorrect - The complement system is not directly involved in the viral neutralization reaction. B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells. C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing. D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.

Correct Answer: D

Rationale: Interferon is a cell-specific protein that is produced and released from infected cells in response to viral infections. It acts extracellularly to interfere with viral replication, not to inactivate the virus itself. Interferon is not coded for by cellular DNA, but by viral RNA during infection. Therefore, the correct answer, D, is that interferon is not virus-specific but is cell-specific. This is because interferon can be produced by various cell types in response to different types of viral infections, making it a broad-spectrum antiviral defense mechanism.

Correct Answer: B

Rationale: The correct answer is B: Transduction. In bacterial genetics, transduction refers to the process of DNA transfer from one bacterium to another via bacteriophages. During transduction, the bacteriophage infects a bacterium, incorporating bacterial DNA into its own genome, which is then transferred to another bacterium upon infecting it. Rationale: A: Transfection is the process of introducing foreign DNA into eukaryotic cells, not bacteria. C: Induction is the process of activating gene expression in a cell. D: Infection is a general term for the invasion of pathogens into a host organism, not specific to DNA transfer via phages in bacteria.

Correct Answer: C

Rationale: The correct answer is C (100°C) because the Koch apparatus is used for sterilization, and the standard temperature for sterilization is 100°C. At this temperature, most microorganisms are killed, making it an effective method for sterilization. Choice A (90°C), B (95°C), and D (110°C) are incorrect because they are not commonly used temperatures for sterilization purposes. Choosing a temperature lower than 100°C may not effectively kill all microorganisms, while choosing a temperature higher than 100°C may lead to unnecessary energy consumption without providing additional sterilization benefits.