Primary Immune Response Initiation

Steps:

• Macrophages engulf and present antigens to naive T helper cells via MHC.
• Activated T helper cells proliferate and differentiate.
• T helper cells release cytokines to stimulate B cells and macrophages.
• B cells differentiate into plasma cells, producing antibodies.

Why B is correct:

• It accurately describes the initial cascade: macrophages present antigens to activate T helper cells, which then secrete cytokines to amplify the response, per adaptive immunity principles.

Why the others are wrong:

• A: Reverses roles; B cells do not activate T cells—it's the opposite.
• C: Includes irrelevant neutrophils and confuses differentiation with memory selection.
• D: Describes secondary response activation via memory cells, not primary.

Final answer: B