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White Blood Cells Morphology and Counts

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					White Blood Cells
Morphology and Counts
Clinical Pathology
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.
Storage-Maturation Compartment
• Cells mature into metamyelocytes→ band
  cells→ Segmented cells.
• 80% of granulocytes are found in the bone
  marrow of healthy animals.
   • These cells are released from bone
     marrow with the oldest (segmented) to
     increased peripheral need.
   • In less than two days, the bone marrow
     can respond.
   • Dogs have the largest storage pool (5
     days) whereas bovines have limited
     storage.
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
Neutrophils
• Primary functions:
   • Phagocytosis and killing of microbes.
   • Usually circulate for 10 hours before
     migrating into the tissues.
   • Ingest material and eventual bacterial
     killing.
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 hig
    numbers of eosinophils.
Basophils
     • Secrete mediators of
       inflammation (histamine)
       associated with hypersensitivity
       reactions.
     • This release occurs when
       antigens complex with IgE is
       located on the cellular surface.
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
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 invloved 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 hemtopoiesis.
   • Cause bone marrow to produce more
       granulocytes.
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.
B cell
T cell
Normal morphology
• 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.
Neutrophil compartments in
Peripheral blood
• Marginated neutrophil pool: during any
  moment of time, some neutrophils are
  loosely adhered to the vessel wall. These
  cells are not sampled when blood is drawn
  from non-stressed animals.
• Circulating neutrophil pool: neutrophils
  moving with RBC’s and fluid. Are sampled
  pool of cells.

• When an animal is stressed- marginated
  pool becomes circulating pool. Called
  stress leukogram.
Response to Inflammation
• Inflammatory cells at sites of inflammation release
  substances (cytokines, interleukins) into the blood
  to attract neutrophils.
• Segmented neutrophils are released from the
  mature storage compartment in the bone marrow.
• Increase in peripheral numbers (measurable in 2
  days).
• If sudden demand for neutrophils depletes the
  storage compartment of segmented neutrophils,
  then band cells are released.
• With continued depletion, cells in bone marrow
  begin to divide.
• When source of inflammation is removed, demand
  for neutrophils decrease, and production slows
  down.
Immature Neutrophils in
Circulation
• Immature neutrophils in circulation (left shift)-
  defined as the release of immature neutrophils
  (usually bands) into the circulation to meet tissue
  demand.
• The appearance of immature neutrophils is termed
  “Left shift”.
   • Regenerative left shift: the absolute number of
      neutrophils in circulation is increased. The bone
      marrow has increased the neutrophil release.
   • Degenerative left shift: the nummber of
      neutrophils has decreased. This is a poor
      diagnostic sign.
Cattle exception:
• Adult cattle have a relatively low absolute
  number of neutrophils in circulation and
  have a small marrow storage pool.
• A degenerative left shift is typical of the
  acute inflammatory response in cattle.
Some terminology for morphology
• -penia: decreased number of cells in the blood
  (Neutropenia, lymphopenia).
• -philia or –cytosis: increased number of cells in the
  blood (neutrophilia, lymphocytosis).
• Left shift: increased numbers of immature
  neutrophils in the blood.
• Leukemia: neoplastic cells in the blood or bone
  marrow.
• Leukemoid response: marked leukocytosis
  (>50,000/ul) usually a result of inflammatory
  disease.
• Lymphoproliferative disorders: conditions in
  lymphocytes or plasma cells proliferate abnormally.
• Myeloproliferative disorders: a group of bone
  marrow disorders, usually neoplastic, which stems
  from on of the bone marrow cell lines.
Neutrophilia
• Not always due to infection.
• Stress leukogram: endogenous or exogenous
  corticosteroids.
   • Characterized by neutrophilia without a left
      shift, monocytosis, lymphopenia, and
      eosionopenia.
   • Caused by a shift from the marginal to the
      circulating pool.
• Physiological luekocytosis: transiet condition
  caused by excitement, epinephrine release and
  splenic contraction.
   • Neutrophilia without left shift and normal or
      increased lymphocyte number.
   • Occurs more commonly in the cat than the dog.
Inflammatory Leukogram
• Increased bone marrow proliferation, shift
  from storage pool to blood.
• Mild inflammation yields a leukocyte
  response similar to stress.
• Purulent reaction: neutrophils with a left
  shift.
   • Intense response with left shift
   • Can confuse immature cells of myeloid
     series with neoplasia (leukemia)
• Degenerative shift usually is due to
  extreme migration of cells into tissues
  and/or detrimental side effects of toxins.
Toxic Neutrophils
• Characterized by ctyoplasm basophilia,
  Dohle bodies, toxic granulation, and/or
  foamy cytoplasm.
• Cells have decreased functional abilities.
• Animal with toxic, degenerative shift may
  be compromised by lack of adequate cell
  number and decrease ability of cells to
  function.
Dohle Bodies
• Blue cytoplasmic inclusions.
• Low numbers may be found in healthy
  cats.
• Indicates toxicity in other species.
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.
Pelger-Huet Anomaly
• Hyposegemented neutrophils that function
  normally.
• Hereditary disorder; failure of the nucleus
  in mature cells to undergo segmentation.
Lymphocytosis
• Physiologic: due to epinephrine release.
   • Common in chronic inflammation and
     chronic antigenic stimulation.
   • Later stages of resolving infections.
• Neoplastic lymphocytosis such as
  leukemia and lymphosarcoma
Lymphopenia
•   Common finding on CBC
•   Associated with stress
•   Immunosuppressive therapy
•   Immunodeficiency syndrome
•   Viral infections such as parvo.
    Reactive Lymphocytes
• Characteristic changes in the morphology of
  lymphocyte that has been stimulated to
  produce antibody (B cells) or lymphokines (T
  cells).
• Morphological changes: increased cytoplasm,
  increased basophilia of cytoplasm, increased
  aggregation of chromatin, and may lack
  perinuclear clear zone.

				
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posted:12/16/2011
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