Leukocytes

What are leukocytes?

White blood cells (WBCs) and their precursors that defend the body against infection

What is the process of WBC formation called?

Leukopoiesis

What are WBCs formed from?

Hematopoietic stem cells

Where does leukopoiesis mainly occur?

In the bone marrow

Where do some lymphocytes form?

In lymphoid tissue

What stimulates leukopoiesis?

Colony stimulating factors (CSFs) and other immune stimuli

What are the two main types of leukocytes?

Granulocytes and agranulocytes

Granulocytes have ___ granules

Visible

Agranulocytes have ___ ___ granules

No visible

Name the granulocytes

Neutrophils, eosinophils, basophils

Name the agranulocytes

Monocytes and lymphocytes

How do WBC counts compare to RBC counts?

WBCs are far fewer than RBCs

What factors can alter WBC counts?

Species, stress, exercise, age, infection, immune/endocrine diseases

Main function of leukocytes

Defense (immunity)

What are the two broad immune categories?

Phagocytic (non-specific) and immunocytic (specific)

Name the phagocytic leukocytes

Neutrophils and monocytes

Name the immunocytic luekocytes

Lymphocytes (B & T cells)

What are the three main lymphocyte types?

B cells, T cells, NK cells

Role of B cells

Humoral immunity (antibody production)

Role of T cells

Cell-mediated immunity (cytokines, attack infected cells)

Role of NK cells

Kill tumor or virus-infected cells

List the 3 stages of phagocytosis

Chemotaxis, adherence, ingestion

Chemotaxis

Movement toward signal

Adherence

Attach to target

Ingestion

Engulf and digest

What enhances adherence during phagocytosis?

Opsonization

Opsonization

Coating with antibodies/complement

What is the most common WBC in dogs, cats, and horses?

Neutrophils

Main function of neutrophils

Phagocytosis

What are the first responders against bacteria?

Neutrophils

What are the neutrophil maturation stages?

Myeloblast, promyelocyte, myelocyte, metamyelocyte, band, segmented (mature)

How long do neutrophils circulate in blood?

About 10 hrs

What does “left shift” mean?

Presence of immature neutrophils (bands) in circulation

What conditions cause neutrophilia?

Infections, inflammation, stress

What causes neutropenia?

Excess use, bone marrow suppression, viral infection

What color do eosinophil granules stain?

Red/orange with eosin dye

Main function of eosinophils

Control parasites and allergic reactions (anti-inflammatory)

What conditions cause eosinophilia?

Parasitic infections or hypersensitivity reactions

What do eosinophils inhibit?

Histamine release and mast cell degranulation

What is the least common WBC?

Basophils

What color do basophil granules stain?

Blue/purple

What chemical do basophils release to increase vascular permeability?

Histamine

What chemical prevents coagulation?

Heparin

Basophilia is often associated with what condition?

Allergic or hypersensitivity reactions

What is the largest WBC?

Monocyte

What do monocytes become when they enter tissues?

Macrophages

What system are macrophages part of?

Mononuclear Phagocyte System (MPS) or Reticuloendothelial System (RES)

Main function of monocytes

Phagocytosis of large particles and antigen presentation to lymphocytes

What condition causes monocytosis?

Chronic inflammation or stress

Which WBCs are predominant in bovine and porcine?

Lymphocytes

Where do T-cells mature?

Thymus

Where do B-cells originate?

Bursa equivalent tissue

Provide an example of bursa equivalent tissue

Bone marrow

Leukocytosis

Increased total WBC count

Name common causes of leukocytosis

Infection, stress, tissue necrosis, leukemia, hemorrhage, hemolysis, intoxication

What is eosinophilia associated with?

Parasitism, allergies, Addison’s disease

Causes of lymphocytosis

Lymphatic inflammation, viral infections, young animals, leukemia

Monocytosis indicates what?

Chronic inflammation or bacterial/fungal infection

Basophilia with eosinophilia suggests what?

Allergy

Basophilia without eosinophilia may indicate what?

Mast cell tumor

Key color/feature of neutrophil

Pale pink granules

Key color/feature of eosinophil

Red/orange granules

Key color/feature of basophil

Blue/purple granules

Key color/feature of monocyte

Large, vacuolated

Key color/feature of lymphocyte

Round nucleus, thin cytoplasm