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.

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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=KiLJl3NwmpU&NR=1&feature=fvwp-Macrophage

http://www.youtube.com/watch?v=ce0Xndms1bc

http://www.youtube.com/watch?v=k_GPGrl5HDM&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 bodyThese 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

lymphocytelymphoblast

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