Week 3: Leukocytes

Hypersegmented neutrophils

- A neutrophil with more than 5 segments. - An old neutrophil - Needs to be removed from circulation by the body

Segmented neutrophil

- A normal, mature neutrophil nucleus will have 2-5 segments. - Nickname "segs". - The segments are not separate pieces of nucleus, they are joined by a thin strand of chromatin.

Eosinophils

- A white blood cell containing granules that are readily stained by eosin. - Frequently, the segmented nucleus only has two lobes. - An eosinophilia can be seen during allergic reactions and parasitic infections.

Band neutrophil

- An immature neutrophil - Has a "horseshoe" nucleus with NO segmentation. - Seen in the peripheral blood when an increased demand is exceeding the current supply of mature neutrophils.

White blood cells

- Any nucleated cell normally found in blood is a white blood cell. - When white blood cells accumulate in one place, they grossly appear white. - There are 5 types of white blood cells, neutrophils, eosinophils, monocytes, lymphocytes, and basophils.

Basophils

- Basophils are the leukocyte least often seen in circulation, and for this reason, they are the least understood. - Basophil granules are blue and fill the cytoplasm. - Basophils most often have a 2-3 lobed nucleus. - They are the least phagocytic of the granulocytes.

Manual differential

- Counts the 1st 100 WBC's seen on the slide and report the # of each type - Will also comment on the RBC and platelet morphology

Reactive lymphocytes

- Increase in overall size - Increase in nucleus, cytoplasm ratio - May contain vacuoles

Agranulocyte features

- Monocytes and Lymphocytes - There are no specific staining granules in their cytoplasm.

Monocytes

- Monocytes make up 5-6% of the circulating white blood cells. - They are the largest leukocyte. - They have abundant cytoplasm that stains gray-blue and may contain vacuoles of varying sizes. - The nucleus can be round to globular, but it does not split up into any distinct segments. - Monocytes are the major phagocytic cells. - When they enter tissues, they are called macrophages. - A monocytosis is often associated with chronic inflammatory conditions.

Lymphocytes

- Normally the predominant leukocyte in ruminants and pigs. - The only leukocyte with no phagocytic capabilities. - Lymphocytes have a round or oval nucleus that is NOT segmented. - There are several types of lymphocytes: T-cells, B-cells, Plasma cells - Decrease in size with age - Small = more mature - Viruses, swelling

Toxic neutrophils

- Occurs with severe inflammatory disease or toxemia. - Morphologic features include: Basophilic cytoplasm, Döhle bodies, Abnormal nuclear shapes, Vacuoles

Total Leukocyte Count & Manual Differential

- One type of leukocyte can elevate the entire leukocyte count. - To find out which one, it is necessary to look at a blood film. - Using a 5-key counter, 100 leukocytes are counted, keeping track of which types were seen. - This procedure is called the Differential count. - Because you are counting 100 cells, the number of each cell type can be expressed as a percentage. - The percentages can then be expressed as an actual number.

Leukocyte function

- The function of all leukocytes is to provide a defense for the body against foreign invaders. - Each type of leukocyte has its own unique role in this defense. - The white cells primarily do their jobs in the tissues.

Leukocyte formation

- The general term for the formation of leukocytes is leukopoiesis. - All white blood cell production starts in the red bone marrow from the same stem cell that produced red cells. - Each type of leukocyte has its own stimulus for production

Neutrophils

- The most numerous leukocyte in circulation in the dog, cat and horse. - Neutrophil granules do not stain any color, so they are said to be neutral. - Depending on the animal, the granules may appear grey to clear. - Identification of neutrophils is commonly based on nuclear morphology, rather than granule staining characteristics.

Granulocyte features

- They are named for the color of the granules in their cytoplasm when viewed on a stained blood film. - The substances found in the granules determine the function of a granulocyte. - For example: neutrophil granules contain lysosomal enzymes, which aid in killing microorganisms that have been engulfed by the neutrophil.

Ehrlichia inclusions

- Tick born rickettsial infection - The inclusions are termed morulae (sing. morula)

Eosinophil functions

1. Anti-inflammatory response - They are attracted to & inhibit local allergic reactions. - Their granules contain anti-inflammatory substances. 2. Phagocytosis - Eosinophils have minimal phagocytic capabilities but are especially effective as an antiparasitic.

Granulocyte

A group of leukocytes containing granules in their cytoplasm; neutrophils, eosinophils, basophils.

Agranulocytes

A group of leukocytes without granules in their nuclei; lymphocytes, monocytes.

Leukopenia

Abnormally low white blood cell count

Left shift

Above normal count of band neutrophils, commonly seen in conjunction with leukocytosis

Leukocytosis

Increase in the number of white blood cells

Leukemia

Neoplastic WBC released into the blood

Basophil function

Their granules contain histamine and heparin: - Histamine helps initiate inflammation and acute allergic reactions. - Heparin acts as a localized anticoagulant to keep blood flowing to an injured or damaged site.

Canine distemper inclusions

These appear as large aggregates of viral particles seen in RBCs and WBCs.

Calculations

Total WBC count = 10,900 /μL Differential: 81% Neutrophils 0.81 x 10,900 = 8829 /μL 9% Lymphocytes 0.09 x 10,900 = 981 /μL 7% Monocytes 0.07 x 10,900 = 763 /μL 3% Eosinophils 0.03 x 10,900 = 327 /μL

2 categories of leukocytes

• Granulocytes 1. Neutrophil 2. Basophil 3. Eosinophil • Agranulocytes 1. Monocyte 2. Lymphocyte