Plasma Cells Secrete Antibodies

Steps:

• Plasma cells differentiate from activated B cells in humoral immunity.
• They specialize in antibody production, not other immune roles.
• Identify functions: rule out phagocytosis (macrophages/neutrophils) and antigen presentation (dendritic cells/B cells).
• Confirm sole function is large-scale antibody secretion for pathogen neutralization.

Why D is correct:

• Plasma cells are effector B cells defined by antibody production (immunoglobulin secretion) per immunology texts like Abbas' Cellular and Molecular Immunology.

Why the others are wrong:

• A includes 1 and 2, but plasma cells do not phagocytose or present antigens.
• B includes 2, but plasma cells do not present antigens to T cells.
• C is only 2, but 2 (antigen presentation) is not a plasma cell function.

Final answer: D