Cytochemistry in hematology
Cytochemistry can be
used to study both red blood cells and white blood cells, although the focus is on the latter. The most common staining techniques
include:
• Myeloperoxidase, an enzyme present most strongly in granulocytes and their precursors, but may
also be present in red cells and their precursors.
• Sudan black, which stains a component of the granules of granulocytes and monocytes, and so
often provides the same information as does myeloperoxidase.
• Neutrophil alkaline phosphatase, an enzyme found predominantly in mature neutrophils.
• Acid phosphatase, an enzyme found in granulocytes, but which is generally used to define certain
lymphocytic leukaemias in peripheral blood. However, in the bone marrow, macrophages and
megakaryocytes are strongly positive. The use of acid phosphatase is one of the few methods that
can be used to detect platelets.
• Periodic acid–Schiff (PAS), a stain used to stain glycogen and related polysaccharides. Although
granulocyte precursors stain weakly, if at all, mature neutrophils show intense staining.
• The esterases, a family of enzymes that are generally used to investigate different leukaemias.
Abnormalities in red cell biology can be investigated using Perls’ stain, which is also known as
Prussian blue. This stain detects the presence of iron-containing molecules inside the cell and so, if
found in a red blood cell, defines a siderocyte. The same stain when applied to a bone marrow aspi-
rate can identify iron within red blood cell precursors such as sideroblasts—these are erythroblasts
with inappropriate deposits of iron, and are associated with a particular type of anaemia.