Primary Immune Response Sequence

Steps:

• Pathogens enter body; macrophages phagocytose them (event 2) to process antigens.
• Processed antigens presented via surface molecules, including initial antibody display on B cells (event 4).
• T-helper cells activate (event 3), aiding cytotoxic T-killer production and B cell stimulation.
• Activated B cells differentiate into plasma and memory cells (event 1), leading to antibody production and release (event 5).

Why B is correct:

• Matches innate-to-adaptive progression: phagocytosis initiates antigen presentation (2-4), T-cell help (3) drives B-cell activation (1) and humoral response (5), per immunology's stepwise activation model.

Why the others are wrong:

• A: Starts with antibody release (5), skipping innate phagocytosis.
• C: Places T-helper activation (3) before B-cell differentiation (1), inverting helper-B cell dependency.
• D: Begins with unclear surface antibody release (4), preceding phagocytosis needed for antigen processing.

Final answer: B