Leukocytes (WBC)_1_Granulocytes and Monocytes

Identification of Granulocytes and Monocytes

  • Terms Associated with Increases and Decreases in Granulocytes and Monocytes
    • Granulocytosis: Increase in granulocytes
    • Granulopenia: Decrease in granulocytes
    • Monocytosis: Increase in monocytes
    • Monocytopenia: Decrease in monocytes

Reference Intervals

  • Adult Reference Intervals for Granulocytes and Monocytes
    • Granulocytes:
    • Normal range: 1.5 - 8.0 × 10^9/L
    • Monocytes:
    • Normal range: 0.2 - 0.8 × 10^9/L

Calculating Absolute Cell Counts

  • Formula for Absolute Cell Count: extAbsolutecellcount(x103/extµL)=extDifferentialcount(indecimalform)imesextWBCcount(x103/extµL)ext{Absolute cell count (x 10}^3/ ext{µL)} = ext{Differential count (in decimal form)} imes ext{WBC count (x 10}^3/ ext{µL)}
    • Example: For a WBC count of 12.0 × 10^3/µL and a neutrophil percentage of 70%:
    • extAbsoluteneutrophilcount=0.70imes12.0=8.4ext×103/extµLext{Absolute neutrophil count} = 0.70 imes 12.0 = 8.4 ext{ × 10}^3/ ext{µL}

Absolute vs Relative Values of Cell Counts

  • Absolute Value: The total number of cells counted in a specific differential type
  • Relative Value: The percentage of that cell type in relation to the total WBC count
    • Example: If the total WBC is 10 × 10^3/µL and neutrophils make up 60%, the absolute count is 6 × 10^3/µL

Factors Affecting Granulocyte and Monocyte Levels

  • Conditions Causing Increase in Granulocyte and Monocyte Counts:

    • Infections
    • Inflammatory reactions
    • Stress responses

  • Conditions Causing Decrease:

    • Bone marrow suppression
    • Autoimmune disorders
    • Certain medications

Comparison of Pediatric and Newborn Reference Intervals

  • Differences in Reference Intervals:
    • Newborns: Higher granulocyte counts (9 - 30 × 10^3/µL) at birth; decline to 5 - 21 × 10^3/µL in the first week
    • Adults: Average WBC count is 4 - 11 × 10^3/µL

Morphological Features of Granulocytes and Monocytes

  • Granulocyte Precursors:

    • Myeloblast, promyelocyte, myelocyte, metamyelocyte, band form, segmented neutrophil
    • Development includes stages with different nuclear and cytoplasmic features

  • Monocyte Precursors:

    • Monoblast, promonocyte
    • Similar development stages with distinct changes in morphology

Cell Lineage and Function

  • Granulocyte Cell Lineage Development:

    • Begins from hematopoietic stem cells (HSC) and progresses through several stages until maturation
    • Functions: Host defense mechanisms including phagocytosis, degranulation, and production of neutrophil extracellular traps

  • Monocyte Cell Lineage Development:

    • Similar progression from HSC to monocytes
    • Functions: Antigen presentation, phagocytosis, cytokine release

Processes Involving Neutrophils

  • Neutrophil Migration:
    • Neutrophils move to infection sites via chemotaxis
  • Phagocytosis:
    • Involves engulfing pathogens and utilizing reactive oxygen species, enzymes, and other molecules for destruction
  • Neutrophil Extracellular Traps (NETs):
    • Web-like structures that trap and kill pathogens

Neutrophil and Monocyte Development

  • Cytokine Regulation:

    • Regulated by IL-3, GM-CSF, G-CSF
    • Key growth factors for stimulation and survival

  • Stages of Neutrophil Maturation:

    1. Myeloblast
    2. Promyelocyte
    3. Myelocyte
    4. Metamyelocyte
    5. Band neutrophil
    6. Segmented neutrophil

Changes During Maturation

  • Morphological Changes:
    • Nucleus: Changes from round, high N:C ratio, to segmented during maturation
    • Cytoplasm: Gradual increase in granulation and color change from basophilic to neutral staining

Summary of Cell Characteristics

  • Myeloblast Characteristics:

    • Size: 14-20 µm, high N:C ratio, multiple nucleoli, faintly positive for specific markers (CD33, CD34)

  • Promyelocyte Characteristics:

    • Size: 15-21 µm, more prominent granules containing peroxidase

  • Myelocyte Characteristics:

    • Size: 12-18 µm, may exhibit two forms, divide up to three times

  • Metamyelocyte Characteristics:

    • Size: 10-18 µm, nuclear indentation starts to occur

  • Band Neutrophil Characteristics:

    • Size: 9-15 µm, indentation is significant, first stage in peripheral blood

  • Segmented Neutrophil Characteristics:

    • Size: 9-15 µm, possess multiple lobes, filled with diverse granules

Clinical Implications

  • Normal Values:

    • Granulocytes: 1.5 - 8.0 × 10^9/L
    • Monocytes: 0.2 - 0.8 × 10^9/L

  • Infectious Disease Response:

    • Generally reflected by an increase in neutrophil count over 7.0 × 10^3/µL, suggesting a reactive response to bacterial infections or tissue necrosis

  • Test Results Interpretation:

    • Example case study of Harry, a 30-year-old male: WBC count of 12 × 10^3/µL may indicate infection; Examination of specific results regarding reference intervals could imply further clinical assessment is needed, especially in newborns due to different normal ranges.