Leukocytes and Hematology

A nucleated white blood cell that travels through blood to reach tissues, where it functions.

All leukocytes in the body, including bone marrow precursors, circulating leukocytes in blood, and tissue leukocytes.

A blood test evaluating leukocytes, usually as part of a CBC.

1. An increase in total leukocytes above the reference limit.
2. Neutrophilia, or heterophilia in species with heterophils.

1. A decrease in total leukocytes below the reference limit.
2. Neutropenia

Decreased numbers of all leukocyte types in the blood.

Decreased leukocytes, RBCs, and platelets.

In the buffy coat with platelets.

About 1 leukocyte per 500–1,000 RBCs.

Neutrophils/heterophils, eosinophils, and basophils.

Lymphocytes and monocytes.

Defense, inflammation, homeostasis, and immunity.

First-line defense against bacterial infection during acute inflammation.

Defense against helminths (parasites) and participation in allergic reactions.

They become macrophages.

Phagocytosis, antigen processing/presentation, and production of inflammatory mediators and cytokines.

Humoral and cell-mediated immunity, antibody/cytokine production, self vs. non-self recognition, and immune memory.

To determine whether tissue injury/inflammation is occurring and what type of response is present.

Disease presence/type of inflammation, disease severity, progression, and prognosis.

Infections, neoplasia, and inherited leukocyte disorders.

Circulating leukocytes constantly move between blood and tissues.

Total WBC count, differential count, and absolute leukocyte counts.

All nucleated cells counted by the analyzer, including nucleated RBCs if present which will need to be corrected

The percentage of each leukocyte type among the total leukocyte population.

uses total leukocyte count x differential %

22,500 neutrophils/µL.

They provide the best evaluation of the leukon and are compared with reference intervals.

-philia, such as neutrophilia.

-cytosis, such as lymphocytosis.

-penia, such as neutropenia or lymphopenia.

Multiple lobes separated by constrictions or filaments.

Their cytoplasmic granules take up little stain with routine stains.

Primary/azurophilic and secondary/specific granules.

Proteases, acid hydrolases, peroxidase, lysozyme, and microbicidal cationic proteins.

In its lysosomal granules.

Release of antimicrobial enzymes and proteins from neutrophil granules.

O₂-dependent (respiratory burst and generation of ROS) and O₂-independent killing.

1. IL-3, GM-CSF, and G-CSF.
2. G-CSF

Increase proliferation and promote neutrophil differentiation and maturation.

It increases proliferation, shortens maturation time, increases neutrophil function, and promotes marrow release.

Increase the number of functioning neutrophils at the site of injury.

Phagocytosis and microbicidal action.

Integrins binding endothelial ICAMs.

PECAM and other adhesion molecules.

C5a, C567, Factor XIIa, LTB4, IL-8/CXCL8, PAF, and bacterial products.

Adherence → ingestion/phagocytosis → degranulation → microbial killing.

O₂-dependent microbial killing.