[Campbell Biology P.1014] Which of the following statements correctly describes a step in the... | Practice Question

Which of the following statements correctly describes a step in the activation of a B cell during the humoral immune response, as depicted in Figure 43.19?

  • A: An antigen-presenting cell directly activates a B cell by secreting cytokines.
  • B: Helper T cells recognize antigen fragments presented by B cells on Class II MHC molecules.
  • C: Activated B cells primarily differentiate into memory T cells for long-term immunity.
  • D: Secreted antibodies directly destroy pathogens by engulfing them.

Explanation

Figure 43.19, step 2, clearly illustrates that after a B cell internalizes an antigen and displays a fragment on its Class II MHC molecule, an activated helper T cell with specific receptors binds to this complex to activate the B cell.