Unit 3 Note Summary

UNIT 3 Evaluation of the Leukon

General Objectives

• Understand basic principles of leukon evaluation.

Specific Objectives

1. Define leukon.

2. Discuss two groups of leukocytes.

3. Identify leukocytes in each group.

4. Detail stages of granulocyte development.

5. Discuss developmental changes in leukocytes.

6. List stages of monocyte development.

7. Define macrophages.

8. List stages of lymphocyte development.

9. Discuss morphology and function of white blood cells (WBCs).

10. Recognize each white blood cell.

11. Discuss lymphocytes in detail.

12. Define heterophil.

13. Understand key terms used in the unit.

14. Discuss methods of counting white blood cells.

15. Identify factors affecting leukocyte count.

16. Identify two systems for categorizing WBCs.

17. Describe the purpose of WBC classification systems.

18. Identify WBC types in each system and their functions.

19. Interpret leukon responses in various physiological/disease processes.

20. Understand species-specific leukon responses.

Evaluation of the Leukon

Definition

• Leukocytes (WBCs) protect the body against infections and foreign substances.

Classification of Leukocytes

• Granulocytes: Contain granules; includes neutrophils, eosinophils, basophils.

• Agranulocytes (Lymphoid Cells): Few or no granules; includes lymphocytes, monocytes.

Production of Leukocytes

• Occurs primarily in the bone marrow (leukopoiesis).

Granulocyte Development Stages

1. Myeloblast: Large, prominent nucleoli, no visible granules.

2. Promyelocyte: Larger, small reddish-purple granules, round nucleus.

3. Myelocyte: Smaller, few specific granules (eosinophils/basophils).

4. Metamyelocyte: Kidney-bean shaped nucleus, specific granules present.

5. Band Cell: Nucleus U or S shaped, not fully segmented.

6. Segmented Granulocyte: Lobulated nucleus, 2-5 lobes, specific granules evident.

White Blood Cell Systems

• Phagocytic System: Neutrophils, eosinophils, basophils.

  • Function: Ingest and destroy pathogens (Phagocytosis)

  • Includes Chemotaxis, Adherence, Internalization.

• Immunocytic System: Lymphocytes, monocyte/macrophage continuum.

  • Function: Produce antibodies & kill pathogens.

Functions of Specific Granulocytes

Neutrophils

• Predominant WBC; primary defense against bacterial infection.

• Short lifespan, circulating briefly before migrating to tissue.

• Functions: Ingest bacteria, secrete enzymes and factors for tissue response.

Eosinophils

• Contain granules for allergic reactions/parasites.

• Limited understanding of functions.

• Increased in conditions like allergic reactions and parasitic infections.

Basophils

• Least common; responsible for allergic responses.

• Release histamines and heparin.

Monocyte/Macrophage Series

• Monocytes are precursors to macrophages.

• Functions: Phagocytosis, antigen processing, recruiting other WBCs.

• Increased in inflammatory responses.

Lymphocytes

• Continuous monitoring for antigens; predominant in cattle.

• Types: T Cell (Cell-mediated immunity) and B Cell (Humoral immunity).

• Variability in counts based on species and age.

Interpretation of the Leukogram

• White cell count, morphology, and differential counts evaluated in CBC.

• Counting techniques: Manual (hemacytometer), differential blood count, electric cell counters.

• Factors affecting leukocyte counts include age, breed, exercise, and physiological states.

Inflammatory Responses

• Inflammation increases blood circulation and leukocyte migration.

• Neutrophils show most significant response with left shifts indicating higher immature neutrophils.

• Responses classified as regenerative (adequate marrow response) or degenerative (poor prognosis).

Stress and Excitement Responses

• Stress response causes lymphopenia, mild neutrophilia, and eosinopenia due to glucocorticoids.

• Excitement leads to physiological leukocytosis through increased circulation due to epinephrine.

Miscellaneous Morphological Changes

• Toxic Neutrophils: Altered morphology due to inflammation; larger, with inclusions.

• Hypersegmented Neutrophils: Aging neutrophils remaining in circulation longer.

• Chediak-Higashi Syndrome: Genetic disorder affecting granule function in leukocytes.