white blood cells

• White blood cells (WBC)


  • Produced from hematopoietic stem cells in response to infection
  • Granulocytes: contain cytoplasmic granules (neutrophils, eosinophils, basophils)
  • Agranulocytes: absence of prominent granules (monocytes, lymphocytes)
• Neutrophils


  • Phagocyte that defends against bacteria, contain enzymes to digest bacteria, polymorphonuclear with multi-lobed nucleus
• Eosinophils


  • Defend against endoparasites (parasitic worms), have deep red granules
• Basophils


  • Defend against ectoparasites, release histamines for inflammation, release heparin to inhibit blood clotting, have deep blue granules
• Monocytes


  • Change into macrophages and destroy bacteria by phagocytosis, largest WBC
• Lymphocytes


  • Main WBC in lymph, account for 25-35% of circulating WBC, some can live for years
  • Natural killer (NK) cells destroy infected or cancerous cells
  • T lymphocytes: cellular immune response, include helper T cells, cytotoxic T cells, memory T cells
  • B lymphocytes: humoral immune response, include plasma cells that secrete antibodies, memory B cells