Immune Response Sequence in Transplant Rejection

Steps:

• B-lymphocytes first bind to antigens on donor kidney cells, initiating activation (step 3).
• Activated T-lymphocytes then secrete cytokines to amplify the response and aid cell differentiation (step 1).
• Cytokines promote precursor T cells to differentiate into cytotoxic T-killer cells (step 5).
• Activated B-lymphocytes differentiate into plasma cells, producing antibodies that target and destroy donor cells via complement activation or opsonization (step 2).

Why B is correct:

• It follows the standard primary immune response pathway where antigen binding (3) triggers T-cell cytokine release (1) for helper signals, leading to T-killer differentiation (5) and B-cell antibody production (2) for targeted cell lysis.

Why the others are wrong:

• A starts with cytokine secretion (1) before antigen recognition, violating activation sequence.
• C places killing by T-killer cells (4) before cytokine secretion (1), but cytokines precede effector functions.
• D begins with T-killer differentiation (5) without prior antigen or T-cell activation.

Final answer: B