Influenza viruses infect humans and elicit an immune response that is often insufficient to protect the individual from sickness or death. Which of the following structures are on influenza viruses, allowing them to be recognized by the human immune system?

Correct Answer: C

Rationale: The molecules on the virus that are not on host cells are the pathogen-associated molecular patterns. The pattern recognition receptors are found on host cells and molecules. MHC I and II molecules are present on all nucleated host cells but not on viruses. The somatically generated receptors are on host T and B lymphocytes.

Correct Answer: B

Rationale: Lymphatic circulation deposits cells into the left subclavian vein via the thoracic duct to reenter blood.

Correct Answer: D

Rationale: Memory cells enhance secondary responses; not cyclosporine or passive .

Correct Answer: B

Rationale: Helper T cells bind MHC II ; MHC I is for cytotoxic T cells.

Correct Answer: B

Rationale: Plasma has higher protein content than lymph, which is filtered interstitial fluid with fewer proteins.