In humoral immunity steps, which action follows antigen recognition?

• A. Antigen presentation
• B. Attack
• C. Clonal selection
• D. Differentiation

Answer: (A)

After a B cell’s receptor recognizes its specific antigen, the next action is to present processed antigen fragments on MHC class II molecules to a helper T cell. This antigen presentation is essential because the helper T cell’s recognition, along with signals like CD40L and cytokines, provides the necessary activation to drive the B cell into clonal expansion and differentiation. This sets up the production of antibody-secreting plasma cells and memory B cells. Without this T cell–mediated help, B cells don’t fully activate. The actual attack by antibodies happens once the B cells have been activated and differentiated, following this initial presentation step.