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H&L: Leukograms & Leukocyte morphology

What leukocytes are normally present in peripheral blood?
What are the 3 neutrophil populations, what pools do they contain?
1. Marrow: containing proliferation pool, maturation pool and storage pool
2. Blood: containing circulating (free flowing) and marginated (adhered) pools
3. Tissue
-philia or -osis indicates what?
an increase in leukocyte concentration.
-philia (polymorphonuclear cells)
- osis (mononuclear cells)
What processes lead to neutrophilia?
acute and chronic inflammation
chronic myeloid leukaemia
What processes lead to lymphocytosis?
chronic inflammation
lymphoproliferative disease
lymphoid neoplasia
What processes lead to monocytosis?
monocytic leukaemia
What processes lead to eosinophilia?
Hypersensitivity (allergies)
Eosinophilic leukaemia
Idiopathic disorders
What processes lead to basophilia?
Hypersensitivity (allergies)
basophilic leukaemia
mast cell neoplasia
What is a left shift?
When does it occur?
What does it indicate?
A left shift is an increased concentration of non-segmented neutrophils (usually bands) in blood.

It occurs where there is an increased demand for neutrophils in the blood, the bone marrow meets demand by releasing neutrophils from the store pool and when the storage pool is exhausted more immature cells (bands etc) are released.

It is considered the hallmark of inflammation, and indicates an intense inflammatory stimulus.
When is a left shift
a) regenerative
b) degenerative
a) when the concentration of segmented neutrophils is greater than the concentration of immature (band) neutrophils. The bone marrow is keeping up with demand.

b) when the concentration of immature (band) neutrophils is greater than the concentration of segmented neutrophils. The bone marrow is not keeping up with demand.
-paenia indicates what?
A decrease in leukocyte concentrations
What is the normal reference range for monocytes, eosinophils and basophils?
Close to zero. This is why decreased concentrations not recognised.
What processes lead to neutropaenia?
overwhelming inflammation
reduced production
peripheral destruction
ineffective production
What processes lead to lymphopaenia?
acute inflammation
lymphoid hypoplasia/aplasia
Describe an acute inflammatory leukogram.
Characterised by neutrophillia with a left shift, lymphopaenia and monocytosis.

The magnitude of left shift also gives an indication of the severity of the tissue demand for neutrophils, and how well the bone marrow is coping. The greater the left shift, the greater the tissue demand.
Describe an acute overwhelming inflammation leukogram.
Characterised by neutropaenia with or without a left shift, often neutrophilic toxic changes and lymphopaenia.

In endotoxaemia there is a rapid shift of neutrophils from the circulating pool to the marginated pool resulting in neutropaenia.
Describe a chronic inflammatory leukogram.
Characterised by mature neutrophilia (with no or a minor left shift), lymphocytosis and monocytosis.

This indicates chronicity of inflammation in which there has been time for hyperplasia of the neutrophil series in the bone marrow, therefore there is no longer a need for a release of immature neutrophils (resolving left shift).
Describe a glucocorticoid stress leukogram
Characterised by mature neutrophilia with lymphopaenia and monocytosis.

The presence of increased concentrations of glucocorticoids in circulation results in the down regulation of cell adhesion, causing a shift of neutrophils and possibly monocytes rom the marginated blood pool to the circulating pool.
What species differences exist regarding the normal ratio between the marginated and circulating neutrophil pools?
In dogs, horses and cattle, the ration is approximately 1:1. So neutrophils can be expected to double with stress/glucocorticoids.

In cats, the ratio is close to 2:1, therefore neutrophil concentrations can potentially triple.
Describe a physiological leukocytosis leukogram
Characterised by mature neutrophilia, lymphocytosis with or without monocytosis.

This leukogram is seen in response to excitement/adrenaline (flight or fight). It is most common in young animals and in cats. The increase in neutrophils and lymphocytosis reflects increased blood flow which shifts neutrophils from the marginated pool to the circulating pool.

As with the stress leukogram, neutrophil concentrations can double in most species and triple in cats.

This leukogram is transient and the abnormalities are expected to return to normal quickly (within an hour) once the stimulus resolves.
Describe a leukogram that reflects generalised bone marrow disease or selective granulocytic hypoplasia.
Characterised by persistent or worsening neutropaenia that is unexplained by other causes. There is usually no left shift or toxic changes present.

This may also be accompanied by non-regenerative anaemia with or without thrombocytopaenia.
Describe a hypoadrenocorticism (Addison's disease) leukogram.
Typically a sick animal would be stressed - so we expect a stress leukogram, potentially an inflammatory leukogram if inflammation is present.

We should ALWAYS think of Addison's if you have an obviously stressed dog with a normal to decreased neutrophil concentration and a high to normal increased lymphocyte concentration (because stress should cause the opposite).
Describe a leukogram that reflects leukaemia.
Findings are variable and reflect the type of leukaemia. Often there is a marked leukocytosis with abnormal/immature cells in circulation that can't be explained by other reasons. Diagnosis is made by excluding all other causes.
What important species differences should be considered when interpreting leukograms?
Dogs have the most pronounced acute inflammatory leukocytosis,

Cats and young animals most commonly have physiologic leukocytosis leukograms.

Horses often have little or no neutrophilia during inflammatory states

Cattle have very small bone marrow neutrophil storage pools, so inflammatory states tend to cause neutropaenia initially before the bone marrow has had time to respond by increasing production.
What abnormalities are regarded as toxic changes?
Foamy cytoplasm
Diffuse cytoplasm
Dohle bodies (note: some healthy cats may have low numbers in health)
Asynchronous nuclear maturation
Giant neutrophils
Toxic granulation
What features of reactive lymphocytes have?
What cells can they be mistaken for?
Increased cytoplasm
Increased cytoplasmic basophilia
Prominent golgi zone
irregular nuclei shape
nucleoli rarely visible

They can be mistaken for neoplastic lymphocytes.
What are hypersegmented neutrophils? When do we see them?
These neutrophils have more nuclear lobulations than usual, this indicates that the neutrophils are ageing/old.
This is usually a consequence of down regulation of endothelial cell adhesion molecules and therefore reduced transit of neutrophils into tissues - usually due to increased blood concentrations of glucocorticoids.
What are erythrophages?
what are they associated with?
Monocytes that have engulfed an erythrocyte. They are rare in peripheral blood and usually associated with immune-mediated haemolytic anaemia.
What parasites can be found in leukocytes?
Bacteria, distemper inclusions, Leishmania, Toxoplasma. Although finding organisms in leukocytes is rare.
what hereditary disorders have leukocyte morphology abnormalities?
Chediak-Higashi syndrome and Pelger-Huet anomaly.