Matching immune cell functions in primary response

Steps:

• Identify cell 2 as the destroyer of virus-infected cells: cytotoxic T-killer cell.
• Identify cell 4 as the phagocyte that engulfs antigens: macrophage.
• Identify cell 1 as the cell binding antigens via receptors: B-lymphocyte.
• Identify cell 3 as the precursor producing more B-lymphocytes upon activation: B-lymphocyte.

Why C is correct:

• C aligns with immune definitions: B-lymphocytes bind antigens and proliferate, T-killer cells lyse infected cells, macrophages phagocytose via released enzymes.

Why the others are wrong:

• A: Macrophages do not destroy infected cells; T-killer cells do not produce B-lymphocytes; T-helper cells do not engulf.
• B: Invalid cell types like T-macrophage and B-killer cell do not exist.
• D: T-killer cells do not primarily bind free antigens; T-helper cells do not destroy infected cells.

Final answer: C