Lymphocytes

• Lymphocytes have very little cytoplasm, forming a thin halo around a large round purple staining nucleus
• Lymphocytes are the primary cells of the lymphatic system, a network of special vessels and organs distinct from, but connected to, those of the cardiovascular system
• Lymphocytes are responsible for specific immunity
• The circulating blood contains three functional classes of lymphocytes

  • T cells (T lymphocytes) enter peripheral tissues and attack foreign cells directly
  • B cells (B lymphocytes) differentiate into plasma cells, which secrete antibodies that attack foreign cells or proteins
  • Natural killer (NK) cells are responsible for immune survelillance and destruction of abnormal cells