Blood
Cell Identification by Staining and Morphology
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White blood cells
comprise a diverse collection of leukocytes mediating a variety of
immunologically related functions. Individual cell types can be microscopically
distinguished by
gross morphology and by staining with cytochemical dyes. For example,
Wright-Giemsa stain, with its combination of acidic and basic dyes, will
differentially stain the granules, cytoplasm,
and nuclei of various blood cell types as illustrated by some
of the images linked to this University of New England Faculty Histology Lab VII Cardiovascular System webpage.
Differential staining
morphology of different blood cell types
|
Red Blood Cells (RBCs)
|
Monocytes |
| cytoplasm = orange-pink to rose |
cytoplasm = pale gray-blue
nucleus = deep bluish-purple |
| Lymphocytes |
Neutrophils (PMNs, Polys) |
cytoplasm = light blue
nucleus = deep blue-violet |
granules = purple-to-lilac
cytoplasm = pale pink
nucleus = deep blue-violet |
| Eosinophils: |
Basophils |
| granules = orange to pink |
granules = deep blue to violet |
|
Platelets |
|
central granules = red-purple surrounded by light blue |
Morphologically, white blood cells are classified
into two broad categories -- granulocytes and mononuclear cells.
Granulocytes typically have multi-lobed nuclei
(often shaped like sausages on a string) and a granular cytoplasm. There are three
basic types of granulocyte:
-
Granulocytes,
- Neutrophils, also
referred to as polymorphonuclear cells, or more simply PMNs
- Eosinophils; and
- Basophils, the
blood-borne precursors of mast
cells.
|
Mononuclear cells, which typically have rounded
or kidney-shaped nuclei and often little cytoplasm, are comprised of two basic cell types:
-
Monocytes, the
blood-borne precursors of macrophages and
-
Lymphocytes,
which are morphologically classified as small and large, comprise a heterogeneous mixture of functionally distinct cell types,
including B lymphocytes, the precursors of antibody-producing
plasma cells, several types of T
lymphocytes, and natural killer (NK) lymphocytes.
|
In addition to their distinctive cytochemical
staining characteristics, blood cells can be distinguished on a gross level by their
average size and granularity as measured by flow cytometry. With a flow cytometer, the optical effects of passing a single cell
through a laser light beam can be measured in terms of light scattered by the cell in two
directions -- parallel to the beam ("forward scattering" or FSC) and perpendicular to the beam ("side scattering" or SSC). Greater FSC correlates with larger cell size while greater
SSC correlates with more granularity in the cytoplasm and nucleus of a cell. A
two-dimensional plot of
FSC versus SSC for human
blood cells, reveals that different cell types exhibit distinct average ranges of size
and granularity. Thus, flow cytometry can be used to analyze and even physically isolate
different blood cell populations.
With a modified flow cytometer designed to detect
fluorescent light stimulated by the laser beam, i.e., a
fluorescence-activated cell sorter (FACS), even
finer distinctions between different cell populations can be made if they have been
treated with fluorescently tagged monoclonal antibodies directed against specific cell
surface molecules, generically referred to as
cluster of
differentiation (CD) antigens.
References:
- J. D. Bauer, Clinical Laboratory Methods
(9th ed.) Mosby, St. Louis, p. 111 (1982)
Cells & Organs of the
Immune System
Cluster of Differentiation
(CD) Antigens