Lymphocytes

Question 1

Lymphocyte Kinetics

Answer 1

• Relatively long lived cells
  
  • weeks, months, years
• Retain ability to divide
• Recirculate
  
  • average transit time in blood is 30 minutes
  • Total recirculation time varies
    
    • 1-several hours
• Although plasma cells are differeniated B-cells
  
  • We do NOT see plasma cells in the blood in health

Question 2

Lymphocyte Kinetics In Health

Answer 2

• Circulate in blood between lumph nodes and other lymphoid organs/tissue
• Blood Lymphocytes:
  
  • distributed between mariginating and circulating pools
  • May travel to tissue and re-enter the blood

Question 3

Lymphocytosis:

Chronic Inflammation

Answer 3

• Bacterial infections
  
  • Ehrlichia canis
• Fungal infections
  
  • primarily systemic
• Viral infections
  
  • FLV, BLV, EIAV
• Protozoal infections
  
  • babesial and theilerial
• Typical Concurrent Leukogram Abnormalities
  
  • Neutrophilia
  • Monocytosis
  • Occasionally +/- eosinophilia and or basophilia

Question 4

Lymphocytosis:

Physiologic Lymphocytosis

Answer 4

• Fight or Flight response:
  
  • excitement, fright, pain, exercise, anxiety
• Catecholamine injections:
  
  • epinephrine or norepinephrine
• Young animals:
  
  • cats and horses most common
• Shift from marginating to circulating pool
• Usually lasts minutes to hours
• Morphologic changes in lymphocytes are NOT expected.

Question 5

Lymphocytosis:

Lymphoid Neoplasia

Answer 5

• Lymphoma
• Lymphoid Leukemia
• Increase production of neoplastic lymphocytes from the spleen (leukemia)
• Increased production of neoplastic lymphocytes form the lymph node (lymphoma)
• Increased production of neoplastic lympocytes from soft tissue (lymphoma)

Question 6

Reactive Lymphocytes

Answer 6

• Immune stimulated lymphocytes
• Upregulated synthesis
  
  • inflammatory mediators
  • Immunoglobulins
• Active, systemic antigenic stimulation secondary to both infection and noninfectious disorders

Question 7

Lymphopenia:

Acute inflamamtion

Answer 7

Homing

Increased migration to inflamed tissue

• Most acute inflammatory leukograms
• Increase migration to inflamed tissue
• Decreased migration from LN to blood
• “Homing” to lymph nodes

Question 8

Lymphopenia:

Corticosteroids

Answer 8

Low dose → cells stay in tissues

High dose → kill lymphocytes

Stress leukogram

• Decreased lymphopoiesis in lymph nodes
• Decreased efflux from lymph node
• Cytotoxic effects in the lymph node
• Immediate shift form circulating pool to marrow and Lymph node

Question 9

Lymphopenia

Other important, less common causes

Answer 9

• Lymphoid aplasia or hypoplasia
  
  • immunosuppressive or radiation therapy
  • Neoplasia or inflammation
  • Inherited T cell deficiencies
  • Acquired T cell deficiencies
  • Thymic aplasia
• Depletion
  
  • loss of lymphocyte-rich lymph