Leukocyte Development and Immune Functions

Leukocytes

White blood cells involved in immune response.

Hematopoietic Stem Cell

Stem cell that gives rise to all blood cells.

Granulocytes

Leukocytes with granules in their cytoplasm.

Mononuclear Cells

Leukocytes with a single, non-segmented nucleus.

Neutrophils

Most abundant leukocytes, involved in phagocytosis.

Eosinophils

Leukocytes that combat parasitic infections.

Basophils

Leukocytes involved in allergic reactions.

Monocytes

Leukocytes that differentiate into macrophages.

Lymphocytes

Key players in adaptive immunity.

Cytokines

Signaling molecules that mediate immune responses.

G-CSF

Granulocyte colony-stimulating factor, stimulates neutrophil production.

Kinetics

Movement of cells through developmental stages.

Promonocytes

Precursor cells that develop into monocytes.

Myeloblasts

Immature cells that develop into granulocytes.

Promyelocytes

Stage in neutrophil development with basophilic granules.

Myelocytes

Stage in neutrophil development with distinct granules.

Metamyelocytes

Mature stage of neutrophil development before band cells.

Band Neutrophils

Immature neutrophils with band-shaped nuclei.

Segmented Neutrophils

Mature neutrophils with lobulated nuclei.

Hematogones

Immature B cells found in bone marrow.

Natural Killer Cells

Lymphocytes that attack virus-infected cells.

Plasma Cells

B cells that produce antibodies.

Mast Cells

Cells involved in allergic responses and inflammation.

Immune Response

Body's defense mechanism against pathogens.

Flow Cytometry

Technique to identify leukocyte types via surface antigens.

Romanowsky Stain

Staining technique for visualizing blood cells.

Reference Interval

Normal range for leukocyte counts in blood.

Acute Myeloid Leukemia

Cancer characterized by rapid growth of myeloblasts.

HSCs

Hematopoietic stem cells, origin of blood cells.

CMPs

Common myeloid progenitors, precursors to myeloid cells.

GMPs

Granulocyte-monocyte progenitors, lead to granulocytes.

Type I Myeloblast

High N:C ratio, no visible granules.

Type II Myeloblast

Contains few azure granules, larger than Type I.

Type III Myeloblast

More heterochromatin, nucleoli absent.

Myelocyte

Final mitotic stage, produces secondary granules.

Metamyelocyte

Indented nucleus, no division capability.

Band Neutrophil

9% to 32% of marrow cells, indented nucleus.

Segmented Neutrophil

7% to 30% of marrow cells, lobed nucleus.

Proliferation Pool

Stage where cell division occurs.

Maturation Pool

Stage for storage of mature cells.

Stem Cell Pool

Reservoir of hematopoietic stem cells.

IL-3

Interleukin-3, stimulates hematopoiesis.

GM-CSF

Granulocyte-macrophage colony-stimulating factor.

Primary Granules

Formed during promyelocyte stage, last to release.

Secondary Granules

Formed during myelocyte stage, contain specific proteins.

Tertiary Granules

Formed during metamyelocyte stage, second to release.

Secretory Granules

First to release, contain surface proteins.

Neutrophil

Most abundant leukocyte, fights infection.

Cytoplasmic Basophilia

Presence of RNA, indicates cell maturity.

Nucleus-to-Cytoplasm Ratio

Indicator of cell maturity, varies by cell type.

Dawn of Neutrophilia

Early myelocyte stage, secondary granules appear.

Clinical Utility of Band Counts

Controversial, often included in neutrophil counts.

Pediatric Neutrophil Values

Differ significantly from adult values.

Pediatric leukocyte values

Leukocyte percentages differ significantly in children.

Circulating Neutrophil Pool (CNP)

Neutrophils freely circulate in the bloodstream.

Marginated Neutrophil Pool (MNP)

Neutrophils loosely adhere to capillary walls.

Neutrophil half-life

Neutrophils survive approximately 7 hours in blood.

Neutrophil production rate

Production is 0.9 to 1.0 x 10^9 cells/kg/day.

Proliferative pool

Contains about 2.1 x 10^9 neutrophils.

Maturation pool

Holds roughly 5.6 x 10^9 neutrophils.

Diapedesis

Process for neutrophils to exit blood into tissues.

Apoptosis

Programmed cell death of neutrophils.

Bcl-2 family

Regulates neutrophil apoptosis via pro- and anti-apoptotic signals.

Neutrophil rolling

Transient adhesion to endothelial cells during migration.

Chemokines

Facilitate neutrophil activation and rolling on endothelium.

Integrins

Molecules that stabilize neutrophil adhesion.

Transmigration

Neutrophils move through endothelial cells to tissues.

Phagocytosis

Process of engulfing and destroying pathogens.

Surface receptors

Recognize pathogens or opsonic molecules for phagocytosis.

Pseudopodia

Extensions of neutrophils that surround pathogens.

Phagosome

Vesicle formed around engulfed particles in neutrophils.

Respiratory burst

Activation of NADPH oxidase producing reactive oxygen species.

Oxygen-independent killing

Digestive enzymes function in neutral pH phagosome.

Neutrophil Extracellular Traps (NETs)

DNA and enzymes expelled to trap pathogens.

Chemotaxis

Movement of neutrophils towards chemical signals.

Eosinophil characteristics

Large reddish-orange granules in eosinophil myelocytes.

Reactive oxygen species

Molecules generated to kill pathogens during phagocytosis.

Myeloperoxidase (MPO)

Enzyme that converts hydrogen peroxide to hypochlorite.

Primary lysosomes

Contain hydrolytic enzymes for pathogen digestion.

Secondary lysosomes

Fuse with phagosomes to release bactericidal molecules.

Bilobed nucleus

Characteristic nuclear shape of mature eosinophils.

Secondary granules

Granules that increase in number during maturation.

Secretory granule

Granule type involved in secretion processes.

Tertiary granules

Granules that degrade extracellular matrix.

NETs

Extracellular traps formed by dying neutrophils.

NETosis

Neutrophil death resulting in NET formation.

Transcobalamin I

Protein necessary for vitamin B12 absorption.

Eosinophil kinetics

Study of eosinophil development and turnover.

Myelocyte division time

3.5 days from myelocyte to mature eosinophil.

Eosinophil turnover rate

Approximately 2.2 x 10^8 cells/kg per day.

Storage pool

9 to 14 x 10^8 eosinophils/kg in marrow.

Primary granules

Contain Charcot-Leyden crystal protein.

Degranulation

Process of eosinophils releasing granule contents.

Classical exocytosis

Granules fuse with plasma membrane to release contents.

Compound exocytosis

Granules fuse together before membrane fusion.

Piecemeal degranulation

Selective release of specific proteins from granules.

Cytolysis

Release of intact granules during cell lysis.

Eosinophil lifespan

Circulating half-life is approximately 18 hours.

Tissue survival time

Eosinophils survive 2 to 5 days in tissues.

Eosinophil functions

Roles include immune regulation and inflammation.