Unit 4 - Study Notes on Leukocyte Disorders

LEUKOCYTE (WBC) DISORDERS

Overview

• Leukocytes (White Blood Cells): Key players in the immune response and are crucial for identifying and combating infections.
• Symptoms and Causes: Various disorders involving leukocytes can affect the immune status of individuals. Raising awareness of these disorders can aid in diagnosis and treatment.

Key Terms and Suffixes to Remember

• Philia: Indicates an increase in cell numbers.
• Cytosis: Refers to an increase in the number of blood cells.
• Penia: Refers to a decrease in cell numbers.
  • These terms collectively can denote a disease process where the numbers of specific leukocyte types are either increased or decreased.

Clinical Definitions

• Leukocytosis: An increase in the number of WBCs in circulation above reference range due to various causes. It considers the sum of all WBCs.
• Leukopenia: A reduction in the number of WBCs in circulation.
• Left Shift: Indicates the appearance of increased numbers of immature WBCs in blood circulation, typically seen as Band cells. Neutrophils predominantly determine the presence of a left shift in most species.

Neutrophil Population and Left Shift

• The left shift signifies a higher demand for leukocytes, leading to the release of immature forms (Band forms) into circulation.
• Image Reference: Band Neutrophil from Canine blood (Cornell University College of Veterinary Medicine).

Classification of Left Shift

1. Regenerative Left Shift:
   • Increased white cell count with more immature WBCs than mature ones, indicating an early response to increased demand for leukocytes.
2. Degenerative Left Shift:
   • Normal or low white cell count with immature cells outnumbering mature cells, usually indicating a longer-standing condition; may suggest the body cannot keep up with demand, commonly seen in severe infections or sepsis.

CBC Values for Consideration

• Example of blood values recorded in laboratory settings:
  

• Indicates an increase in neutrophils with a left shift and can show systemic immune responses.

Species Differences in Observing Left Shift

• Dogs and Cats: Exhibit a left shift with a large pool of WBCs in the bone marrow.
• Cattle and Horses: Smaller maturation pools lead to quicker depletion and less frequent left shifts; typically display leukopenia instead.

Toxic Changes in Neutrophils

• When immature cells are released from the bone marrow, they may show toxic changes, including:
  1. Cytoplasmic Basophilia
  2. Toxic Granulation
  3. Toxic Vacuolation
  4. Dohle Bodies: Indicative of cytoplasmic immaturity, common in cats and early signs of toxic changes.

Quantitative WBC Disorders

• Abnormalities in leukocyte number can be classified into:
  1. Benign: Good immune responses, lymphocytes, and inflammatory responses.
  2. Malignant: Abnormal proliferation, e.g., leukemia indicates cancer processes.

Margination Concept

• Leukocytes can become sticky and adhere to blood vessel walls, forming a marginated pool that waits to move into the tissues.

Neutrophilia Definition

• An increase in the absolute number of neutrophils in circulation above normal for that species.
• Possible Reasons for Neutrophilia:
  1. Short-term physiological stress (Epinephrine effect).
  2. Prolonged stress (Corticosteroids).
  3. Inflammation demands (infections).

Physiologic Neutrophilia

• Caused by endogenous epinephrine leading to a mild, short-term response where neutrophils shift from marginated to circulating measurements without any toxic changes.

Stress Neutrophilia

• Resulting from prolonged release of corticosteroids, shows neutrophils elevated in circulation but less movement to tissues, leading to chronic stress conditions harmlessly appearing as elevated neutrophil counts.

Inflammatory Neutrophilia

• Demonstrates actual increased demand for neutrophils due to inflammatory processes; presence of neutrophilia, possibly left shift, and toxic changes may occur.

Monocytosis

• An absolute increase in monocytes often coincides with neutrophilia during chronic or long-standing inflammatory processes.

Eosinophilia

• An absolute increase in eosinophils associated with conditions like GI diseases, parasitic infections, and allergic reactions.

Lymphocytosis and Lymphocytopenia

• Lymphocytosis: Increase in lymphocytes; could indicate neoplasia or viral processes.
• Lymphocytopenia: Commonly seen in veterinary practice, often due to stress-related corticosteroid release.

Leukopenia

• Defined as decreased numbers of WBCs below normal ranges, can open discussions about various leukocyte types like neutropenia or lymphocytopenia.

Neutropenia Types

1. Increased Demand: Due to acute infections or inflammation, may present with a left shift.
2. Reduced Production: Can be highlighted by viral infections affecting vitamins and nutrients vital for blood cell production.
3. Ineffective Production: The bone marrow malfunctions or is unable to release adequately maturing cells.
4. Sequestration: Neutrophils trapped in tissues, leading to a drop in circulating counts, often in inflammatory conditions like septic shock.

Malignant Disorders Affecting WBCs

• Leukemia: Characterized by abnormal proliferation of WBCs often containing immature cells, hinting at underlying malignancy.

Lymphoproliferative Disorders**

• Malignant conditions affecting the lymphoid system, such as lymphoma, that can cause abnormal WBC profiles during diagnostics.