basophilic

Basophilic is a term used in histology and pathology to describe cellular or tissue components that have an affinity for basic (alkaline) dyes, resulting in a blue to purple appearance under standard stains such as hematoxylin. This is the opposite of acidophilic (eosinophilic), which stain with acidic dyes. Basophilia reflects the presence of acidic, negatively charged molecules that bind basic dyes, notably nucleic acids and certain ribonucleoproteins.

In routine histology, basophilic structures include cell nuclei, where DNA and RNA-rich regions bind hematoxylin, giving a blue-black color. Other basophilic elements are components of the cytoplasm rich in ribosomes or rough endoplasmic reticulum, which contain abundant RNA. Basophilic staining can also be observed with other basic dyes such as toluidine blue.

The term is also used in hematology. Basophils are a class of white blood cells that stain with basic dyes and appear with dark blue-purple granules on standard stains. Basophilia, an increase in basophil numbers in blood, can be associated with allergic reactions, inflammatory states, and certain myeloproliferative disorders such as chronic myelogenous leukemia. Conversely, basophilic stippling refers to punctate blue inclusions in red blood cells due to aggregated RNA, seen in conditions like lead poisoning and sideroblastic anemia.

Overall, basophilic character describes staining properties rather than a single structural feature, and it is a common descriptor in diagnostic pathology and cytology.