orthochromatophilic

Orthochromatophilic is a term used in microscopy, particularly in histology and cytology, to describe a specific staining characteristic of cellular components. It refers to the staining of cellular structures with a mixture of acidic and basic dyes in a way that produces a neutral color, typically purple or grey. This contrasts with structures that stain orthochromatically, meaning they take on the color of the acidic or basic dye alone.

The most common application of orthochromatophilia is seen with Romanowsky stains, such as Wright's stain or Giemsa stain, which are widely used for differential blood counts and the examination of blood and bone marrow smears. These stains contain both eosin (an acidic dye that stains basic cellular components pink or red) and methylene blue (a basic dye that stains acidic cellular components blue or purple). When cellular components have a neutral charge or a balanced mixture of acidic and basic properties, they will stain orthochromatophilically, resulting in a lilac or grayish-purple hue.

Examples of structures that commonly stain orthochromatophilically include the nucleus of mature red blood cells (erythrocytes) and the cytoplasm of certain white blood cells, such as neutrophils. This neutral staining is a key indicator for identifying and classifying different cell types in a microscopic examination. The precise shade of orthochromatophilic staining can vary slightly depending on the specific stain formulation, the tissue preparation, and the staining technique employed. Understanding orthochromatophilia is essential for accurate interpretation of cytological and histological specimens.