Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils
Mnemonic
“Never Let Monkeys Eat Bananas”, in order of decreasing abundance:
- N - Neutrophils, 40 to 75 per cent. Acute bacterial infection, phagocytosis
- L - Lymphocytes, 20 to 45 per cent. Viral infection, adaptive immunity
- M - Monocytes, 2 to 10 per cent. Become tissue macrophages, chronic infection
- E - Eosinophils, 1 to 6 per cent. Parasites, allergy
- B - Basophils, under 1 per cent. Histamine, and chronic myeloid leukaemia
“60, 30, 6, 3, 1” is the rough percentage version, easier to recall for calculating absolute counts.
The neutrophil to lymphocyte swap is the single most useful pattern: neutrophilia with lymphopenia suggests bacterial infection or steroids, while lymphocytosis with a normal or low neutrophil count suggests viral infection.
Basophilia is rare and therefore informative, pointing to a myeloproliferative disorder.
Expansion
| Cell | Proportion | Main role | Raised in |
|---|---|---|---|
| Neutrophil | 40 to 75% | Phagocytosis of bacteria | Bacterial infection, inflammation, steroids, stress |
| Lymphocyte | 20 to 45% | Adaptive immunity | Viral infection, tuberculosis, lymphoproliferative disease |
| Monocyte | 2 to 10% | Phagocytosis, antigen presentation; becomes a macrophage in tissue | Chronic infection, tuberculosis |
| Eosinophil | 1 to 6% | Parasites, allergy | Allergy, asthma, parasites, drug reaction, vasculitis |
| Basophil | under 1% | Histamine release | Myeloproliferative disease |
Neutrophilia with a left shift (immature band forms) suggests acute bacterial infection. Steroids cause neutrophilia by demargination, not by increased production.
Neutropenia below 0.5 x 10^9/l constitutes a serious infection risk and, with fever, is a medical emergency.
Eosinophilia is worth a specific list: allergy and asthma, parasites (especially helminths), drug reactions, Churg-Strauss and other vasculitides, adrenal insufficiency, and lymphoma.
Lymphopenia occurs in HIV, steroids, chemotherapy, and severe acute illness including sepsis.