Hematology: lymphocyte

Overview

• T-lymphocytes (cell-mediated immunity) and B-lymphocytes (precursors of plasma cells) - humoral antibody/immunoglobulin production populations; a small, third group are 'null' cells - function unknown.
• May not be differentiated on the basis of light microscopic morphology alone.
• T-lymphocytes, in particular, can recirculate between blood and lymph nodes.

Uses

In combination

• With other red and white blood cell parameters as part of routine hematological screen (CBC) .

Result data

Normal (reference) values

• May vary with age, sex or breed.
• 1 - 4.8 x 10*9/l.
• 0.8-3.8 x 10*9/l (racing Greyhound).
• Varies with age:
  • 0.3-0.6 years old <2.0 x 10*9/l.
  • 0.6-2 years old <1.5 x 10*9/l.
  • >2 years old <1 x 10*9/l.

Abnormal values

• Lymphocyte numbers decrease with increasing age.
• Normal values may be significant in a systemically ill animal, eg lymphoproliferative disorders , hypoadrenocorticism .
  Increased production may not result in lymphocytosis due to marked loss into tissue.
• Lymphoproliferative disorders - normal or slightly raised numbers significant in systemically ill animals. Atypical or bizarre forms may be seen. Occasionally see a very marked increase.

• Lymphocytic leukemia and lymphosarcoma (occasionally see pronounced increase).
• Chronic infections (immunostimulation) or immune stimulation, eg pyoderma , pneumonia , pyometra .
• Hypersensitivity.
• Autoimmune diseases.
• Hypoadrenocorticism .
• Post-vaccination.

• Iatrogenic steroid administration.
• Hyperadrenocorticism .
• Stress (endogenous steroid release).
• Chylothorax .
• Protein-losing enteropathy .
• Lymphosarcoma .
• Granulomatous or inflammatory diseases of lymph nodes.
• Chemotherapy, eg azathiaprine .
• Radiotherapy .
• Chronic renal failure (due to prolonged azotemia).
• Inherited deficiency of T-cells +/- B cells (Miniature Dachshund) .
• Systemic infections :
  • Lymphopenia seen in early viral infections (incubation and viremic phases), followed by rebound increase, except in canine distemper where lymphoid depletion persists.
  • Canine distemper (may also lead to acquired T-cell deficiency).
  • Infectious canine hepatitis .
  • Canine parvovirus .
  • Canine coronavirus .
  • Toxoplasmosis .
  • Leishmaniasis.
  • Demodicosis .
  • Septicemia, especially endotoxemia.

Errors and Artifacts

• Puppies - peak value at ~ 6 weeks, decreasing to adult value by 2 years.
• 0.3-0.6 years old 2-4.8 x 10*9/l.
• 0.6-2 years old 1.5-4.8 x 10*9/l.
• >2 years 1-4.8 x 10*9/l.

Sources

Publications

Other sources of information

• Cowell R L, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. Mosby, St Louis.
• Duncan J R, Prasse K W & Mahaffy E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, Ames, Iowa.
• Jain N C (1993) Essentials of Veterinary Hematology. Lea & Febiger, Philadelphia.