Types of Leukocytes

There are five distinct classes of leukocytes (white blood cells) that coordinate to provide defence against infectious disease:


  • Most abundant type of white blood cell and the first responder to microbial infection
  • They are unable to renew their lysosomes and die after having phagocytosed a few pathogens (forms the majority of pus)
  • Analogy:  Standard police officer – quick to respond to the situation, but lacks special training or skills and so dies rapidly


  • Prominent at the sites of allergic reactions and parasitic infections (rare in blood but common at mucous membranes)
  • Do not phagocytose pathogens but instead release chemical products which perforate cell membranes
  • Consequently, they function as the primary response to large multicellular parasites (e.g. helminth infections)
  • Analogy:  Fumigator – specialised to deal with pests / parasites (e.g. helminths) by releasing chemical products


  • Basophils are chiefly responsible for initiating inflammatory responses by releasing the chemicals histamine and heparin
  • Functionally they are similar to mast cells, however they circulate in the bloodstream whereas mast cells are localised
  • Because they promote inflammation, they are common contributors to allergic responses
  • Analogy:  Fireman – the leukocyte involved when a region is inflamed (‘in flames’)


  • Monocytes are the largest type of leukocyte and share phagocytosis duties with neutrophils
  • They are slower to respond than neutrophils but are longer lasting, as they can renew their lysosomes for continued digestion
  • Monocytes will differentiate into two types of cells in response to pathogenic infection – macrophages and dendritic cells
  • Macrophages will remain in the tissue and phagocytose, whereas dendritic cells present antigen fragments to lymphocytes
  • Analogy:  Riot police (macrophage) – slower to respond than standard police but better prepared and survives for longer
  • Analogy:  Signalman (dendritic cell) – identifies the pathogen and sends signals to the appropriate special forces (lymphocytes)


  • Lymphocytes are responsible for the production of antibodies which target specific antigens present on pathogens
  • They are more common in the lymphatic system than blood and are slowest to respond (requiring antigen presentation)
  • Lymphocytes include B cells (which become antibody-secreting plasma cells) and T cells (which mediate B cell activity)
  • Lymphocytes are also involved in the destruction of virus-infected body cells (via cytotoxic T cells and natural killer cells)
  • Analogy:  Special forces / superheroes – takes longest to mobilise but specially trained to target specific pathogens

Types of Leukocytes

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  Click on the diagram to show as an analogy

Prevalence of Leukocytes

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The relative proportions of the different types of white blood cells are:

Neutrophils (roughly 60 – 70%)

 Lymphocytes (roughly 20 – 30%)

 Monocytes (approximately 1 – 6%)

 Eosinophils (approximately 1 – 3%)

 Basophils (less than 1%)

Mnemonic:  Never Let Monkeys Eat Bananas