Leukocytes
(WBC)
Blood components
All blood cells arise from the same stem cell. In
response to various chemical messengers,
called cytokines, the stem cells begin to
differentiate into one of two types, myeloid or
lymphoid.
Further differentiation in response to additional
cytokines results in forming cell types. The
primary cytokine responsible for erythrocyte
production is erythropoietin (EPO)
The myeloid line differentiates into
erythroblasts which become erythrocytes,
megakaryoblasts, which become platelets,
and the myeloblast, which become
granulocytes and monocytes.
The lymphoid line differentiates into
lymphoblasts which become lymphocytes.
Left and right shift
WBC count
A total white blood cell count is not necessarily indicative
of the severity of a disease, since some serious ailments
may show a low white cell count.
For this reason, a differential white cell count is
performed. A differential white cell count consists of an
examination of blood to determine the presence and the
number of different types of white blood cells.
This study often provides helpful information in
determining the severity and extent of an infection, more
than any other single procedure used in the examination
of the blood.
WBC
Mature and immature neutrophils, lymphocyte,
monocytes, eosinophils and basophils make up
the leukocytes (WBCs) found on the blood of
most mammals.
Each type of cell plays an important role in the
body’s defense system , and the total
concentration of each type is extremely valuable
in the diagnosis of various diseases.
Definitions page 44 read it.
How Do WBC Work?
http://www.youtube.com/watch?v=KiLJl3N
wmpU&NR=1&feature=fvwp-Macrophage
http://www.youtube.com/watch?v=ce0Xnd
ms1bc
http://www.youtube.com/watch?v=k_GPGr
l5HDM&feature=related
Neutrophil: front line in battle
These are usually the most numerous
leukocytes in the blood and are primarily
responsible for fighting infections
Granulocytes: Neutrophils
Segmented neutrophil: Mature cells
that have a segmented, irregular
shaped nucleus.
lymphocyte
Segmented neutrophil eosinophil
Band Neutrophil: An immature cell
characterized by a horseshoe shaped
nucleus
Hyper-segmented neutrophil: A ‘senior’ cell
that is characterized by having 5 or more
‘lobes’ in the nucleus.
Lymphocyte: guard dog of the body
These are the second most common
leukocyte in the blood and their primary
function is immune regulation.
In the mature cell, the nucleus is round
and occupies most of the cell. These cells
will be slightly smaller than neutrophils
lymphoblast lymphocyte
Monocyte: buzzard in the blood
These are the third most common cell seen in
the blood and they have diverse functions. The
primary function is to seek out invaders and eat
them.
Once they have been called to help fight
an infection, the monocyte will move into
the tissue and transform into a
macrophage (big eater). They can
complete this transformation in about 24
hours
http://www.youtube.com/watch?v=tPT_bG6ASGs&feature=related
Eosinophil: the allergy slayer
Eosinophil : red granules compare the
color to the erythrocytes
Under normal conditions, they do not return to
circulation after reaching the tissue. There are
300 – 400 eosinophils in the bone marrow for
every one circulating in the blood.
Eosinophils are attracted to tissues where there
is a high histamine release. Eosinophils are
parasitocidal (destroy parasites), bacteriocidal
(destroy bacteria) and phagocitic.
Basophils: the unknown stranger
Basophils have a poorly defined function
and are relatively rare in canine and feline
blood
They are produced in the bone marrow
and have a life span of 10 to 12 days
Basophils contain heparin in a bound form
with histamine, serotonin, and hyaluronic
acid., all of which are easily released
Leukocyte Disorders
Leukocytosis is an increase in the total
leukocyte count above the normal upper limit for
the animal species.
This increase is usually a consequence of an in
crease in the total number of circulating
neutrophils, although other cell types may also
be increased.
This increase in leukocytes can be caused by a
normal physiologic response or a disease
condition.
Leukocyte Disorders
Leukopenia is a decrease in the total number of
leukocytes.
It may be balanced, a decrease in all cellular
elements, or it may be confined to a single
element.
It is most likely to occur if there is an
overwhelming microbial infection or viral induced
disease. This decrease occurs as neutrophils
move into tissues
The general causes of neutropenia are related
to alteration in the bone marrow and are
known as the three D’s
1. Degeneration (ineffective cell formation)
2. Depression (reduced cell formation)
3. Depletion (reduced survival in blood)
Degeneration of the marrow is usually the result of a
condition that causes deficiency.
Leukocyte response to steroids
Glucocorticoids produce leukocyte alterations
that are specific to each animal species
Canine: In the dog, increased glucocorticoid
steroids produce a three to four fold increase in
neutrophils and a simultaneous 50 – 60%
reduction in lymphocytes along with the
disappearance of eosinophils
Feline: The cat responds in a similar way to the
dog. An increase in neutrophils, decrease in
lymphocytes and some elevation in monocytes
will be seen.
Read and identify WBC page 44-50