Leukogram

• WBCs in blood concentration

  Leukocytoasis:

  • Neutrophilia - increased amount of neutrophils.
  • Lymphocytosis - increased amount of lymphocytes.
  • Monocytosis - increased amount of moncytes.
  • Eosinophilia - increased amount of eosinophils.
  • Basophilia - increased amount of basophils.

  Leucopenia:

  • Neutropenia - decreased amount of WBC
  • Lymphopenia - decreased amount of lymphocytes
  • Monocytopenia - decreased amount of Monocytes
  • Eosinopenia - decreased amount of Eosinophils.
• Causes of WBC number and morphology change in blood:

  • Infection
  • Inflammation - stress related
  • Endocrine - stress related
  • Lymphoid and myeloid neoplasia
• Neutrophil production

  Bone marrow:

  • Occasional EMH (spleen, liver, other).

  Myeloblast - Progranulocyte - Myelocyte

  • Proliferate and mature.

  Metamyelocyte - band - segmented neutrophil

  • Maturation only
• Cells leaving blood vessels

  There are three steps for this to occur:

  • Marginalisation
  • Adhesion
  • Migration

  Various factors can produce a short from marginal to circulating pool.

  • Epinephrine
  • Glucocorticoids
  • Infection
  • Stress

  Binding selectin receptors on blood vessels to ligands on cell walls.
• Causes of Neutrophilia

  Inflammation:

  • Infections (bacterial, viral, fungal, protozoal)
  • Immune mediated anaemia.
  • Necrosis (including haemolysis, sterile inflammation and FB’s).

  Steroids

  • Stress
  • Steroid therapy
  • Hyperadrenocorticism

  Physiological

  • Epinephrine
  • Fight or flight (excitement, fear, pain, exercise).

  Chronic neutrophil leukaemia

  Paraneoplastic (rectal polyp, renal tubular carcinoma, metastatic fibrosarcoma).
• Neutrophilia - left shift

  Normal movement into the tissue.

  Increased release of marrow storage pool cells:

  • Endotoxemia
  • Acute infection
  • Hypoxia
  • Glucocorticoids

  Demargination of neutrophils:

  • Acute infection
  • Exercise
  • Epinephrine
  • Glucocorticoids

  Decreased Extravasation into tissues

  • Glucocorticoids.

  Expansion of marrow precursor pod:

  • Chronic inflection or inflammation
  • Tumours
  • Rebound from neutropenia
  • Myeloproliferative disorders.
• Neutrophilia - Right shift

  Glucocorticoiods down-regulate adhesion molecules, less neutrophils leave the circulation to die, aged cells remain in circulation.
• Neutrophil toxic change

  Rapid neutropoiesis

  Usually severe bacterial infection

  • Not always - can induce by injecting G-CSF

  Other example associations:

  • Parvo, IMHA, ARF, DIC, neoplasia.
• Indicators of neutrophil toxic change

  Dohle bodies:

  • Indicator of Neutrophilic toxic change.
  • Focal blue-grey cytoplasmic structures (RER/RNA)
  • Isolated findings in some healthy cats.

  Foamy cytoplasm:

  • Dispersed organelles (non-discrete - EDTA).

  Diffuse cytoplasmic basophilia:

  • Persistent of cytoplasmic RNA
  • Includes segmented neutrophils.

  Asynchronus nuclear maturatio:

  • Finely granular nuclear chromatin but in segments.

  
• Neutrophil inclusions

  Bacterial:

  • Ehrlichia, Anaplasma

  Viral:

  • Canine distemper

  Protozoa:

  • Toxoplasma
  • Hepatozon

  Fungi:

  • Histoplasma

  Hereditary/metabolic

  • Chediak-Higashi, Birman cat anomaly, mucopolysidosis.
• Causes of neutropenia

  Inflammation:

  • Per-acute/ overwhelming bacterial infections.
  • Canine distemper virus.

  Decreased production:

  • Infections: Parvovirus, FeLV, toxoplasma.
  • Toxicity: chemotherapy, oestrogen, chloramphenicol (cats).
  • Neoplasia: leukaemia, myelodysplastic, metastatic.
  • Marrow necrosis
  • Myelofibrosis

  Rare:

  • Immune mediated neutropenia
• Approach to neutropenia

  Neutropenia - Not anaemic (adequate platelets) - examine for left shift:

  • If left shift - acute inflammation.
  • No left shift - acute viral infection or acute marrow injury.

  Neutropenia - any combination of: nonregernative aneamia, thrombocytopaenia, neoplastic cells - chronic marrow injury.
• Circulation of lymphocytes

  Once lymphocytes have matured, they circulate continuously throughout the body, acting as sentries to sniff out any invading organism or object. In a naive animal, encounter with antigen leads to the lymphocytes draining to the local lymph node to initiate an immune response. In a primed animal, immune responses can initiate at the local site of invasion.
• Lymphocyte inclusions

  Functional:

  • Large granular lymphocytes.

  Infectious:

  • Ehrlichia
  • Distemper

  Metabolic:

  • Lysosomal storage diseases.
• Lymphocytosis

  Physiological:

  • Catecholamine mediated via splenic contractions (especially cats).

  Chronic inflammation:

  • Chronic antigenic stimulation.
  • May include reactive lymphocytes.
  • Usually with neutrophilia and/or monocytosis.

  Young animals and recent vaccination

  Lymphoproliferative disorder (e.g. FeLV, BLV)

  • May be Lymphopenia in lymphoma.

  Hypoadrenocorticism

  • Loss of normal level of lymphocyte inhibition by glucocorticoids.
• Lymphopaenia

  Stress/steroids:

  • Endogenous or exogenous glucocorticoid
  • Shifts lymphocytes out of circulation and lymphocytolysis.

  Acute inflammation:

  • Bacterial, viral or endotoxaemia.
  • Migration to inflamed tissue and home to lymph nodes.
  • Often with Neutrophilia or neutropenia
  • Correction of lymphpaenia - better prognosis

  Loss of lymph:

  • Chylothorax (drainage) or lymphangiectasia

  Cytotoxic drugs, radiation.

  Immunodeficiency drugs, radiation.

  Lymphoma

  • Lymph nodes pathology and disrupted circulation.
• Monocytes and macrophages

  • Monocytes are a blood resident.
  • Differentiation into macrophages occurs when they enter tissues - take on a more spindle like appearance.
  • Cells responsible for phagocytosis.
  • Results in release of immune mediators e.g. cytokines.
  • May have a ‘reactive’ appearance similar to changes in lymphocytes or like ‘macrophages’ in inflammation.
• Monocytosis

  Inflammation:

  • May imply ‘chronic’.
  • Bacterial, fungal, protozoal.
  • Necrosis; Haemolysis, haemorrhage, neoplasia, infarction, trauma.

  Steroid/ stress:

  • Stress
  • Glucocorticoids (occurs ACTH)
  • Hyperadrenocorticism

  Monocytic/myelomonocytic leukemia

  Monocytopenia not recognised a clinically significant entity.
• Eosinophilia

  Hypersensitivity

  Parasitism

  Hypoadrenocorticism (addisons)

  Paraneoplastic (e.g. mast cell tumour but also others).

  Idiopathic eosinophilic syndromes:

  • E.g. canine eosinophillic bronchopnuemopathy, myositis, feline eosinophilic granuloma.

  Eosinophilic leukaemia (very rare).
• Eosinopaenia.

  Glucocorticoids, stress, inflammation.Many reference intervals include 0.

  
• Basophils

  Extremely rare traffic from blood to tissue - will almost never find on blood smears (especially dogs and cats).

  • Lobes not so well defined.
  • Dense blue granules within cytoplasm.

  
• Nucleated red cells

  Manila and automated counting methods for total WBC's that count nuclei in lysed samples, will needs WBCs correcting for nRBCs.

  Can be present in moderate numbers in regenerative anaemia, lead toxicity.

  EMH and splenic contraction, damaged marrow.

  Present in appropriately high numbers in erythroleukanemia (erythemic myelosis; cats).
• Excitement and stress in blood sampling

  Excitement:

  • Catecholamine:
  • Travel, capture, chutes
  • Handling
  • Mature Neutrophilia
  • Lymphocytosis
  • Especially cats.
  • Resolves within hours or less.

  Steroid/stress:

  • Glucocorticoids:
  • Endogenous
  • Exogenous
  • Mature Neutrophilia
  • Lymphopenia
  • Eosinopenia
  • +/- monocytosis
• Working out the leukocyte count (WBCs)

  Manual - haemocytometer

  • Especially avian/exotics

  Machine (also attempts differentiation)

  • Impedance
  • SCILABC
  • Laser
  • E.g. IDEXX lasercyte
  • Combined laser, impedance
  • Simulatenous: OSI gensis
  • Non-simultaneous: IDEXX procyte
  • Multichannel laser
• Common errors - automated leukograms

  Varying degrees of accuracy - none perfect.

  None count bands, other WBC precursors or nRBCs.

  None report toxic change or WBC inclusions.

  None specifically report atypical or reactive lymphocyte morphology.

  Impedance.

  • Neutrophil count most reliable.
  • May confuse lymphocytes and monocytes.