Learning Objectives
- Identify the morphological differences between a segmented neutrophil and a lymphocyte.
- Distinguish between granulocytes and agranulocytes in a peripheral smear.
- Understand the nuclear-to-cytoplasmic (N: C) ratio in different white blood cells.
- Recognize the clinical roles of innate vs. adaptive immune cells.
Overview of White Blood Cell Comparison
This high-power microscopic view of normal peripheral blood compares two primary types of leukocytes: the neutrophil (part of the innate immune system) and the lymphocyte (the primary cell of the adaptive immune system).
Characteristic Features
- Segmented Neutrophil:
- Nucleus: Multilobed (typically 3-5 lobes) with dense, clumped chromatin.
- Cytoplasm: Abundant with fine, neutral-staining “salmon-pink” granules.
- Lymphocyte:
- Nucleus: Round to slightly indented, very dark (intense) staining, occupying most of the cell.
- Cytoplasm: Scant, appearing as a thin rim of pale blue around the nucleus.
- N:C Ratio: Characteristically high compared to the neutrophil.
Cellular Functions
- Neutrophils: Act as phagocytes that primarily target bacteria and fungi. They are the most numerous WBC in a normal adult.
- Lymphocytes: Include B cells (antibody production), T cells (cell-mediated immunity), and Natural Killer (NK) cells.
Clinical Relevance: Differential Count
- Relative Lymphocytosis: An increase in the percentage of lymphocytes is often seen in viral infections (e.g., Infectious Mononucleosis).
- Atypical Lymphocytes: In certain clinical conditions, lymphocytes may become “reactive,” appearing larger with more abundant, darker blue cytoplasm that “hugs” adjacent RBCs.
- Neutrophilia: A high neutrophil count is typically a hallmark of acute bacterial inflammation or sterile tissue necrosis (like an MI).
