Download 1. GENERAL INTRODUCTION

Undergraduate Course in Veterinary Clinical Pathology
Socrates-Erasmus Programme
Haematology
LECTURE 7.
7 LEUKOCYTES
7-1
OVERVIEW
1. General introduction
2.
Types:
-Functions
-Interpreting changes in blood values
3. Morphological changes
4. General patterns of WBC disorders
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1. GENERAL INTRODUCTION
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1
HEMATOPOIESIS
pluripotent stem cell
CFU- Bone marrow (spleen)
myelopoiesis
CFU-GEMM
CFU-MK
CFU-E
lymphopoiesis
CFU-G
B-Cells
CFU-M
T-Cells
granulocytes
thrombocytes
neutrophils
eosinophils
basophils
Null-Cells
erythrocytes
monocytes
CFU=colony forming unit, G=granulocytic, E=erythroid, M=myeloid, M=monocytic, MK megakaryocytic
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DISTRIBUTION OF GRANULOCYTES
(three compartments)
- myeloblast
- promyelocyte
- myelocyte
BONE MARROW PERIPHERAL
TISSUE
BLOOD
proliferationpool
-metamyelocyte
-banded
granulocytes
maturation
+/-
pool
-segmented
granulocytes
+
Storage
pool
+/+
mature
cell
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DISTRIBUTION OF GRANULOCYTES
(three compartments)
BONE MARROW
proliferation
pool
maturation
pool
storage pool
release
distribution in BLOOD VESSELS
marginalisation, adhesion,
transmigration
utilization in TISSUES
?
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2
DISTRIBUTION OF GRANULOCYTES IN
THE PERIPHERAL BLOOD OF RESTING
DOGS AND CATS
Circulating
g
Pool
dog 50 %
cat 25-50 %
Marginated Pool
dog 50 %
cat 50-75%
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PRACTICAL APPLICATIONS:
1. Ways to evaluate leukocytes:
Bone marrow evaluation:
biopsy/aspirate
Blood sample
-easier to obtain
-reflects
reflects the equilibrium
between
different compartments
Tissue cytology
2. Epinephrine can produce a rapid shift of cells from
marginated to circulating pool, especially in the cat
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BASIC TESTS FOR LABORATORY
EVALUATION OF WBC’S
-Total leukocyte count
(manually, automated or estimated from a smear)
-Leukocyte evaluation in a stained blood smear
(differential count for WBC types and morphology
evaluation)
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3
2. TYPES OF LEUKOCYTES:
FUNCTION & INTERPRETATION
OF CHANGES IN BLOOD VALUES
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TYPES OF LEUKOCYTES
- GRANULOCYTES:
Neutrophils, Eosinophils, Basophils
- MONOCYTES
- LYMPHOCYTES
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NEUTROPHILS
FUNCTION:
-phagocytosis in infectious &
inflammatory conditions
-a central role in the inflammatory
p
process
with many
y functions ((eg.
g
release of cytokines)
Usually
changes in neutrophils
changes in total WBC numbers
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4
NEUTROPHILIA (causes)
- Physiological, non-inflammatory response:
• Epinephrine effect
• Glucocorticoid effect
- Reactive, inflammatory response
• Infection (local – systemic)
Any process which
produces an
inflammatory response
• Tissue necrosis/injury
• Immune-mediated diseases
• Tumour, myeloproliferative disorders
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NEUTROPHILS IN
DIFFERENTIAL BLOOD CELL COUNT
Cell maturation proceeds from left to right,
so a shift to the left means more immature cells, a shift to
the right means more mature/aged cells.
<----- left shift
1
2
----3
right shift ---->
4
5
6
1-myeloblast, 2-promyelocyte, 3-myelocyte, 4-metamyelocyte,
5-band, 6-segmented granulocytes
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NEUTROPHILIC LEFT SHIFT
An increase in immature
neutrophils (eg. band and
metamyelocyte cells) is
known as a left shift and
is a sign of inflammation
-If neutrophil numbers are
increased it is a regenerative
left shift (an appropriate
response to acute inflammation)
- If neutrophil numbers are
within range or decreased, it
is a degenerative left shift
(carries a guarded or poor
prognosis, except in cattle)
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5
Band neutrophil granulocytes, dog
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NEUTROPENIA (main causes)
-infectious agents
(eg parvo, FeLV)
- drugs
- lymphomas
Decreased bone marrow
production
Marginal compartment
sequestration
SHOCK
Increased destruction
or use
- overwhelming bacterial
infection
- toxins
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EOSINOPHILS
SOME FUNCTIONS
- inactivate histamine and similar
toxic materials
- inhibit oedema production
- phagocytosis
essential to allergic responses
and defence against parasites
Eosinophil, horse. Appearance
varies with species
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6
EOSINOPHILIA (main causes)
- Parasitism + allergy (to flea or food/ hypersensitivity)
- Hypereosinophilic syndrome
EOSINOPENIA (causes)
- increased glucocorticoid levels
- acute infection
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BASOPHILS
FUNCTION
release of histamine
(release is modified by eosinophils).
Basophil, horse. Appearance varies with
species
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BASOPHILS
BASOPHILIA
-usually associated with eosinophilia as part of
yp
y reactions
hypersensitivity
- basophilic leukaemia
BASOPENIA rare and significance unknown
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MONOCYTES
FUNCTION
-phagocytosis, particularly of
larger items such as:
- tissue debris
monocytes appear similar in most species
- fungi
- protozoa
- bacteria (brucella spp., mycobact. spp)
- antigen presentation
- secretion of cytokines
- become tissue macrophages
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MONOCYTOSIS (causes)
- chronic inflammation particularly some infections, eg.
listeriosis
- transient monocytosis, perhaps a few days after the onset
of acute inflammation
- increased glucocorticoid levels particularly in dogs
-monocytic, myelo-monocytic leukaemia/other neoplasias
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LYMPHOCYTES
FUNCTIONS
-Humoral (antibody mediated) immunity
-Cell mediated immunity.
lymphocytes, dog
B cells and T cells are not distinguishable on morphological
grounds
- short lived lymphocytes (few days)
- long lived lymphocytes (up to years)
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8
LYMPHOCYTOSIS (causes)
Physiological
- mobilization of cells (lymph drainage)
- epinephrine release (i.e. frightened cats)
Pathological
- recent immune stimulation (i.e. vaccination)
- lymphoid neoplasias
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LYMPHO(CYTO)PENIA ( main causes)
Decrease in lymphopoiesis:
- increased glucocorticoid levels
- acute infection, sepsis, endotoxaemia
- radiation
- immunodeficiency syndrome
- some neoplasias
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3. MORPHOLOGICAL CHANGES
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Toxic changes in neutrophils
Neutrophil hypersegmentation
Morphological
Changes
Changes in lymphocytes:
- reactive lymphocytes
- lymphoblasts
WBC inclusions
Pelger-Huët anomaly
7-28
TOXIC CHANGES IN NEUTROPHILS
toxic neutrophil, nucleated RBC (NRBC), dog
Dohle
body
NRBC
NRBC
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TOXIC CHANGES IN NEUTROPHILS
basophilic cytoplasm, larger neutrophils, dog
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TOXIC CHANGES IN NEUTROPHILS
toxic neutrophils with basophilic and foamy cytoplasm,
Doehle bodies and toxic granulation, dog
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Toxic changes in neutrophils
Neutrophil hypersegmentation
Morphological
Changes
Changes in lymphocytes:
- reactive lymphocytes
- lymphoblasts
WBC inclusions
Pelger-Huët anomaly
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NEUTROPHIL HYPERSEGMENTATION
hypersegmented neutrophil, dog
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11
Toxic changes in neutrophils
Neutrophil hypersegmentation
Morphological
Ch
Changes
Changes in lymphocytes:
- reactive
ti lymphocytes
l
h
t
- lymphoblasts
WBC inclusions
Pelger-Huët anomaly
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COMPARISON OF NORMAL LYMPHOCYTES
AND NUCLEATED RED BLOOD CELLS
(NRBC)
lymphocyte - NRBC, dog
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CHANGES IN LYMPHOCYTES
reactive lymphocytes, dog
small
lymphocyte
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12
CHANGES IN LYMPHOCYTES
lymphoblasts, dog
small
lymphocyte
7-37
Toxic changes in neutrophils
Neutrophil hypersegmentation
Morphological
Ch
Changes
Changes in lymphocytes:
- reactive
ti lymphocytes
l
h
t
- lymphoblasts
WBC inclusions
Pelger-Huët anomaly
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PARASITES
hepatozoon, dog
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PARASITES
ehrlichia organism in a neutrophil, dog
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BACTERIA
neutrophil with phagocytosed bacteria, dog
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Toxic changes in neutrophils
Neutrophil hypersegmentation
Morphological
Changes
Changes in lymphocytes:
- reactive lymphocytes
- lymphoblasts
Parasites / bacteria
Pelger-Huët anomaly
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PELGER-HUËT ANOMALY, dog
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4. GENERAL PATTERNS OF
LEUKOCYTE DISORDERS
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CLINICAL USES OF CHANGES IN WBC
VALUES:ADVANTAGES
Changes can help to:
- detect the existence of inflammatory disease.
prognosis
g
and monitor treatment.
- determine p
- detect some haematopoietic neoplasias.
It is recommended, where possible, to interpret
WBC values over the course of several blood counts
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CLINICAL USES OF CHANGES IN WBC
VALUES: LIMITATIONS
- Usually does not identify specific aetiological agents
- Cannot indicate the site of inflammation
- May not identify
f presence off inflammation,
f
i.e.:
• chronic, non-invasive or mild inflammation
• generalized inflammation may cause less WBC
change, compared with local inflammation.
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COMMON CAUSES OF CHANGES IN WBC
VALUES
NONINFLAMMATORY CAUSES OF WBC CHANGE:
- Epinephrine-induced leukogram
- Glucocorticoid-induced leukogram
- Red cell regenerative response
- Leukaemias
INFLAMMATORY CAUSES OF WBC CHANGE:
- Inflammatory response. Leukaemoid reaction
- Leukopenias
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NON-INFLAMMATORY CAUSES
OF CHANGES IN WBC VALUES
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NON-INFLAMMATORY CAUSES OF CHANGES
IN WBC VALUES
EPINEPHRINE-INDUCED
GLUCOCORTICOID-INDUCED
Causes:
-activity (physiological leukocytosis)
-fear, excitement
Causes:
-increase in exogenous or
endogenous
e
doge ous glucocorticoids
g ucoco co ds
Signs:
-Leukocytosis
( 15.0 - 25.0 (30.0) x 109/L)
-Neutrophilia, without left shift
-Lymphocytes within reference
ranges in most species,
but lymphocytosis common in cats
Signs:
-Leukocytosis
( 15.0 - 25.0 (30.0) x 109/L)
-Neutrophilia, without left shift
-Decrease in lymphocytes and
eosinophils
-In dogs:Monocytosis (mild) 7-49
NON-INFLAMMATORY CAUSES OF
CHANGES IN WBC VALUES
RED CELL REGENERATIVE RESPONSE
-Associated with strongly regenerative anaemias.
-Usually appear as a neutrophilia with left shift, and
sometimes thrombocytosis, as a result of non-specific
stimulation of the bone marrow by
y erythropoietin
y
p
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NON-INFLAMMATORY CAUSES OF
CHANGES IN WBC VALUES
LEUKAEMIAS
In some cases of leukaemia there is a persistent increase
of the affected leukocyte type in blood
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INFLAMMATORY CAUSES OF
CHANGES IN WBC VALUES
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INFLAMMATORY CAUSES
GENERAL INFLAMMATORY RESPONSE
GENERALLY THERE IS:
-Leukocytosis
-Neutrophilia
-Left shift
IN ADDITION, OR INSTEAD, THERE MAY BE;
-Toxic changes in neutrophils
-Monocytosis (especially in chronic inflammation
-Leukopenia (see slide on causes of leukopenia)
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INFLAMMATORY CAUSES
LEUKAEMOID REACTION
Very marked increases in leukocyte number due to an
inflammatory response (up to or >100 x 109/L)
which must be differentiated from Leukaemias !
Some examples:
-pyometra
-severe abscessation
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DIFFERENTIATION OF LEUKAEMOID
REACTIONS FROM LEUKAEMIA:
- clinical evidence of inflammation (including response to
anti-inflammatory treatment)
- toxic neutrophils may occur in leukaemoid reaction
Leukaemoid
reaction
Leukaemia
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LEUKOPENIA
In most domesticated animals, the neutrophil is the
predominant cell, so leukopenia is often caused by
neutropenia. However, in the cow, the lymphocyte is the
predominant cell, so leukopenia is often caused by
lymphopenia.
Main causes are:
-excessive tissue consumption in an inflammatory disease:
e.g. Peritonitis, Septicaemia
-bone marrow injury:
• Infectious agents: FeLV, parvovirus, Ehrlichia canis
• drugs: oestrogens/chemotherapy
• neoplasia
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DEGREE OF WBC RESPONSE IN SEVERAL
SPECIES
Leukopenia
(x109/L)
Leukocytosis (x109/L)
species
Neu/Lym
Ratio
mild
moderate
severe
dog
1.1-3.5
<6
18-30
30-50
50-100
cat
1.8
<6
20-30
30-50
50-75
horse
1.1
<5
12-18
18-30
over 30
cattle
0.5
<4
12-20
18-25
over 25
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LEUKOCYTE RESPONSES IN DOGS AND CATS
WBC
Seg
Band
Epinephrine induced
↑
↑
-
Glucocorticoids1
↑
↑
-
↓
Acute Inflammation
↑
↑
↑
↓/-
↑/-
↑/-
↑/-
↑/-
↓
↓
↑/-
↓/-
Chronic Inflammation2
Overwhelming
3
Lymph
↑ (cat)
↑ = increased, ↓ = decreased, - = no change, ↑/- = variable
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