Lymphocyte differentiation and antibody production

Steps:

• Evaluate statement 1: Incorrect, as B-lymphocytes do not require T-lymphocytes for all activations; T-independent responses allow direct differentiation to memory or plasma cells without T help.
• Evaluate statement 2: Correct, as activated B-lymphocytes differentiate into antibody-secreting plasma cells during humoral immunity.
• Evaluate statement 3: Correct, as some activated B-lymphocytes (or their plasma cell derivatives) secrete antibodies, though primarily plasma cells do; T-lymphocytes do not (noting possible question intent for B-cells).
• Evaluate statement 4: Correct, as plasma cells, derived from B-lymphocytes, are specialized to secrete large quantities of antibodies into blood plasma.

Why D is correct:

• Option D selects statements 2, 3, and 4, which accurately describe B-lymphocyte roles in antibody production per immunology principles.

Why the others are wrong:

• A includes incorrect statement 1 about T-cell dependency.
• B includes only wrong statements 1 and 3.
• C includes incorrect statement 1.

Final answer: D