How are B cells activated?

Question 1 of 5

A. A B cell is activated when it encounters an antigen that matches its B cell receptors and receives cytokines from helper T cells B. B cells are activated when they encounter their twin T cell component C. B cells are activated when red blood cells release cytokines D. B cells are activated when their matching antibodies attach to their surfaces and macrophages release cytokines

Correct Answer: A

Rationale: B cells need antigen binding to BCRs and T-helper cytokines ; no twin T cells , RBCs , or antibody-macrophage mechanism activate them.

Question 2 of 5

Stimulation of the nucleic acid sensing TLRs that reside in endosomal membranes induces the production of a different cytokine response than is produced by stimulation of the plasma membrane TLRs. In part, this distinction is based on the different adapter proteins used by the nucleic acid sensing TLRs, leading to the activation of IRF factors. The cytokine response following stimulation of nucleic acid-sensing TLRs is characterized by production of:

A. The antiviral cytokine, type I interferon B. TNF-Î±, which induces increased vascular permeability C. Antimicrobial peptides by macrophages D. Chemokines that recruit neutrophils

Correct Answer: A

Rationale: Endosomal TLRs (e.g., TLR-3/7/9) produce type I interferon via IRF; TNF-Î± , peptides , or chemokines are plasma TLR-related.

Question 3 of 5

The mechanism of cross-presentation by dendritic cells is an essential pathway for generating CD8 T cell responses to some intracellular pathogens. If this pathway did not exist, we would be highly susceptible to:

A. Intracellular pathogens that can survive inside macrophage endocytic vesicles B. Intracellular pathogens that are able to evade antibody responses C. Intracellular pathogens that do not infect and replicate in dendritic cells D. Intracellular pathogens that can spread from cell to cell by inducing cell fusion

Correct Answer: C

Rationale: Cross-presentation targets pathogens not infecting DCs ; macrophages , evasion , or fusion are less specific.

Question 4 of 5

Acquired immunity is a result of previous exposure

A. serious illness B. to vaccination C. repeated exposure to the same factor D. treatment with penicillin

Correct Answer: B

Rationale: Acquired immunity develops from prior exposure, such as through vaccination, which stimulates the immune system to remember pathogens.

Question 5 of 5

The adaptive immune system is capable of mounting specific responses to particular microorganisms because

A. lymphocytes are able to change their antigen specificity as required to fight infection B. stem cells determine which type of B and T cells to make C. the body contains an enormous diversity of lymphocytes, each with the ability to respond to a different antigen D. stem cells make different antigen receptors depending on the invading microorganism

Correct Answer: C

Rationale: Adaptive immunity relies on a vast lymphocyte repertoire, each specific to a unique antigen, not changing specificity or stem cell-driven receptors.

How are B cells activated?

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