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# White cell kinetics and the lines of defence in inflammation

- Regulation
- Exam priority: medium

In infection, resident macrophages act first, neutrophils pour in within hours, monocytes follow, and the marrow steps up output in days.

Updated Nov 13, 2026

Also called: Neutrophil kinetics, Left shift, Marginated pool

**See it in 3D:** [Hip bone](https://durgical.com/en/anatomy/hip-bone/) · [Spleen](https://durgical.com/en/anatomy/spleen/)

## Key points

- Neutrophils circulate only hours (half-life ≈ 6–8 h) and live 1–5 days in tissue; monocytes circulate about 1 day, then live as macrophages for months.
- About half of blood neutrophils are marginated along vessel walls; epinephrine, exercise and glucocorticoids release them and raise the count within minutes without new production.
- Order of defence: resident macrophages (minutes) → neutrophil influx (hours) → monocyte-derived macrophages (hours to days) → increased marrow output (3–5 days).
- TNF and IL-1 from macrophages make endothelium and stromal cells secrete G-CSF, GM-CSF and M-CSF, which mobilize and expand the marrow output.
- Left shift = more bands and younger granulocytes in blood, a sign the marrow reserve is being drawn on.

## What it is

White cells spend only a short time in blood: they are in transit from the marrow to the tissues where they work. Inflammation calls them up in a fixed order, from cells already in place to cells made new. Cytokines from macrophages and lymphocytes release the marrow reserve within hours and raise marrow production over days, which explains the timing of neutrophilia, left shift and pus formation.

## How it works, step by step

- Bacteria and damaged tissue activate resident macrophages, which phagocytose at once and release TNF, IL-1, IL-6 and chemokines.
- Endothelium expresses selectins and integrin ligands; neutrophils roll, stick and migrate into the tissue (diapedesis) within hours.
- The same signals free marginated neutrophils and empty the marrow storage pool, so blood neutrophils can double or more within hours.
- Monocytes enter more slowly, enlarge into macrophages over hours to days and become the main phagocytes of the later phase.
- G-CSF, GM-CSF and M-CSF raise the division of marrow progenitors; new neutrophils and monocytes appear in blood after 3–5 days.
- Dead neutrophils, macrophages, necrotic tissue and exudate liquefy into pus; fibrin walls the cavity into an abscess until it drains or is absorbed.

## Adult reference values (laboratories differ)

| Parameter | Value | Note |
| --- | --- | --- |
| Total white cells | ≈ 4.5–11 × 10^{9}/L | |
| Neutrophils | ≈ 40–70% | absolute ≈ 1.5–7.5 × 10^{9}/L |
| Band forms |
- *+* **TNF, IL-1 (macrophages)**: Induce colony-stimulating factors and adhesion molecules; release marrow reserve.
- *+* **G-CSF, GM-CSF, M-CSF**: Raise proliferation and release of granulocytes and monocytes.
- *+* **Epinephrine, exercise, glucocorticoids**: Demarginate neutrophils (glucocorticoids also delay their exit to tissue): quick rise in count.
- *−* **Chemotherapy, some drugs, marrow failure**: Cut production: neutropenia, with risk of severe infection below 0.5 × 10^9/L.

## Clinical notes

- Sepsis can raise the count with a left shift, or lower it when consumption outpaces supply; neutropenia in sepsis is a poor sign.
- Febrile neutropenia is an emergency because the first two lines of defence are missing and signs of inflammation (pus, infiltrates) may be absent.
- Recombinant G-CSF shortens neutropenia after chemotherapy by acting on the same marrow signal used in infection.

## Memory aid

Guards on site, sprinters in hours, heavy trucks next, and the factory works overtime in days.

## Test yourself

Think of the answer, then tap the question to see it.

## A patient's white count doubles within 20 minutes of a seizure. Where did the extra neutrophils come from?

From the marginated pool: catecholamines detach neutrophils from vessel walls into the circulating pool; no new cells are made in that time.

## What is the order of the lines of defence in acute bacterial inflammation?

Resident tissue macrophages, then neutrophil invasion, then monocyte-derived macrophages, and finally increased marrow production of granulocytes and monocytes.

## Which cytokines link a tissue infection to increased marrow output?

TNF and IL-1 from macrophages induce G-CSF, GM-CSF and M-CSF from endothelium, fibroblasts and lymphocytes, which act on marrow progenitors.

## What is pus made of?

Dead and dying neutrophils and macrophages, necrotic tissue, bacteria and inflammatory fluid, liquefied by released enzymes.

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## Connections

## See it in 3D 2

The structures of Durgical's 3D anatomy where it happens.

- [Hip bone](https://durgical.com/en/anatomy/hip-bone/)
- [Spleen](https://durgical.com/en/anatomy/spleen/)

## Related topics 5

- [White blood cells: types and functions](https://durgical.com/en/physiology/white-blood-cells-types-and-functions/)
- [The physiology of inflammation](https://durgical.com/en/physiology/the-physiology-of-inflammation/)
- [Hematopoiesis](https://durgical.com/en/physiology/hematopoiesis/)
- [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/)
- [Fever](https://durgical.com/en/physiology/fever/)

## Related conditions 4

- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Neutropenia and drug-induced agranulocytosis](https://durgical.com/en/conditions/neutropenia-and-drug-induced-agranulocytosis/)
- [Febrile neutropenia](https://durgical.com/en/conditions/febrile-neutropenia/)
- [Acute leukaemia (AML and ALL)](https://durgical.com/en/conditions/acute-leukaemia/)

## In Pharmacology 1

- [Filgrastim](https://durgical.com/en/pharmacology/filgrastim/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [WBC count: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003643.htm) (MedlinePlus, US National Library of Medicine, 2024); [Blood differential test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003657.htm) (MedlinePlus, US National Library of Medicine, 2024); [Bacterial Sepsis](https://www.ncbi.nlm.nih.gov/books/NBK537054/) (StatPearls (NCBI Bookshelf), 2025).

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