Orcein staining of leukocytes.

An Orcein staining method has been developed which stains mature and immature leukocytes in blood films and bone-marrow smears. Two different patterns of staining are obtained depending on whether staining is or is not preceded by oxidation. In the latter case, all granulocytes and some monocytes show granular reddish-brown cytoplasmic staining. When prior oxidation is used, the staining is in the form of fine grey or black cytoplasmic granules. All lymphocytes, by both techniques, are negative. It is suggested that Orcein stains sulphated mucosubstances, possibly chondroitin sulphate, which in granulocytes is concentrated in their primary granules.