Antibody-secreting cells — identifying the effector cell type Which immune cell type differentiates to actively secrete antibodies (immunoglobulins) into body fluids?

Introduction / Context:
Humoral immunity depends on antibodies secreted into plasma, lymph, and mucosal secretions. Distinguishing which cell is the dedicated antibody factory helps clarify the roles of B lineage cells versus antigen-presenting or cytotoxic cells.

Given Data / Assumptions:

• B cells undergo activation upon antigen encounter with T cell help (most cases) or T-independent signals.
• Terminal differentiation leads to high-rate immunoglobulin secretion.
• Other leukocytes have different primary functions.

Concept / Approach:
Activated B cells proliferate and differentiate into plasma cells, which are specialized for massive immunoglobulin synthesis and secretion. They exhibit prominent rough endoplasmic reticulum and Golgi apparatus to support high protein output. Memory B cells do not secrete large amounts of antibody until reactivation. T cells, macrophages, dendritic cells, and neutrophils serve other immune roles (cytokine production, antigen presentation, phagocytosis, cytotoxicity) and do not secrete antibodies.

Step-by-Step Solution:

Verification / Alternative check:
Histology shows plasma cells with eccentric nucleus and perinuclear hof (Golgi zone), reflecting their secretory function; serum antibody levels correlate with plasma cell activity.

Why Other Options Are Wrong:

• T cells: coordinate or kill but do not secrete antibodies.
• Macrophages/dendritic cells: antigen presentation and phagocytosis; no antibody secretion.
• Neutrophils: rapid innate responders; no antibody production.

Common Pitfalls:
Assuming all lymphocytes secrete antibodies; only B lineage plasma cells do so constitutively in large amounts.

Final Answer:
Plasma cells