Introduction to Hematology/White blood Cells

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Introduction to Hematology/White blood Cells

• Laboratory Procedures

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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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Terminology

• Erythrocyte Red Blood Cell (RBC)
• LeukocyteWhite Blood Cell (WBC)
• 5 main types of white blood cells which include
  three granulocytes.

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Functions of Leukocytes

• Granulocytes
• Characterized by the presence of cytoplasmic
  granules
• Function of these cells occurs in the tissues,
  not in the bloodstream.
• These cells do not recirculate

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Granulocytes

• Neutrophils
• Basophils
• Eosinophils
• Produced predominately in the bone marrow.
• Capable of mitotic division up to the myelocyte
  stage.
• Responds to an increased demand
• infection
• Takes 3-5 days to influence peripheral numbers.

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Neutrophil front line in battle

• These are usually the most numerous leukocytes in
  the blood and are primarily responsible for
  fighting infections

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Granulocytes Neutrophils
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Segmented neutrophil Mature cells that have a
segmented, irregular shaped nucleus.
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lymphocyte
eosinophil
Segmented neutrophil
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Band Neutrophil An immature cell characterized
by a horseshoe shaped nucleus
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Neutrophil Hypersegmentation

• Neutrophils with five or more nuclear lobes.
• Normal aging change of neutrophils which normally
  occurs in the tissues, not bloodstream.
• May occur with excessive levels of
  corticosteroids from administration or
  hyperadrenocorticism.
• Chronic inflammation.
• Artifactual change in the blood that sits for a
  period of time.

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Hyper-segmented neutrophil A senior cell that
is characterized by having 5 or more lobes in
the nucleus.
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Eosinophils

• Inhibit chemical mediators such as histamine and
  serotonin which are released during allergic
  (hypersensitivity reactions).
• Have phagocytic and bacteriocidal properties
  similar to neutrophils but not as effective.
• Have parasiticidal properties.
• Animals with heartworms may have high numbers of
  eosinophils.

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Eosinophil the allergy slayerEosinophil red
granules compare the color to the erythrocytes
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• 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.

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Basophils

• Secrete mediators of inflammation (histamine)
  associated with hypersensitivity reactions.
• This release occurs when antigens complex with
  IgE is located on the cellular surface.

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Basophils the unknown stranger

• Basophils have a poorly defined function and are
  relatively rare in canine and feline blood,
  however they are thought to have some function in
  inflammatory response

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Normal morphology of Granulocytes

• Neutrophils multiple nuclear lobules separated
  by constrictions.
• Band granulocytes band (horseshoe) shaped
  nuclei.
• Eosinophil Lobulated nucleus and cytoplasm
  containing reddish pink granules.
• Basophil Lobulated nucleus and purple-blue
  (Basophilic) granules.

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Lymphocytes

• Distributed in lymphoid tissue to include lymph
  nodes, spleen, thymus, tonsils, bone marrow, and
  blood.
• Capable of division.
• Recirculate in the blood.
• Functions
• B cells turn into plasma cells which secrete
  immunoglobulins. Usually stayin the lymphoid
  tissue.
• T cells transform into effector cells that
  produce lymphokines which function in mediation
  of cellular immunity.

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• Lymphocyte guard dog of the bodyThese are the
  second most common leukocyte in the blood and
  their primary function is immune regulation.

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• In the mature cell, the nucleus is round and
  occupies most of the cell. These cells will be
  slightly smaller than neutrophils

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B cell
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T cell
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Monocytes

• Differentiate into the cells of the
  mononuclear/phagocyte system present in most
  tissues.
• Become macrophages once they migrate into the
  tissues.
• Capable of multiplying within the tissues.
• Can survive for long periods of time

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Monocyte Functions

• Phagocytosis and digestion of particulate
  material, bacteria, and dead cells.
• Macrophages are less responsive to bacterial
  infections than neutrophils but are more
  effective against fungal infections.
• Synthesis and release of substances involved in
  inflammation and immune response.
• Expressions of immune response by presenting
  antigens to T-lymphocytes.
• Serve as a major source of colony stimulating
  factors and cytokines involved in hematopoiesis.
• Cause bone marrow to produce more granulocytes.

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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.

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• 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

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