Eosinophils - Histology

What are Eosinophils?

Eosinophils are a type of white blood cell that play a crucial role in the immune system. They are part of the granulocyte family, characterized by the presence of granules in their cytoplasm. These granules contain enzymes and proteins that contribute to the cell's immune functions.

How are Eosinophils Identified?

Eosinophils can be identified in histological sections by their distinctive appearance. They typically have a bilobed nucleus, and their cytoplasm is filled with large, coarse granules that stain red or pink with eosin, a common histological stain. This staining characteristic is what gives eosinophils their name.

What is the Function of Eosinophils?

The primary function of eosinophils is to combat parasitic infections and participate in inflammatory responses, especially those related to allergic reactions. They release toxic granules to destroy parasites and modulate the activity of other immune cells by releasing cytokines and chemokines.

What is the Clinical Significance of Eosinophils?

An elevated eosinophil count, known as eosinophilia, can indicate various conditions such as parasitic infections, allergic diseases like asthma and hay fever, and certain autoimmune disorders. Conversely, a low eosinophil count may be observed in conditions such as corticosteroid therapy or acute infections.

How are Eosinophils Studied in Histology?

In histology, eosinophils are often studied using H&E staining (hematoxylin and eosin), which highlights their granules and nuclear morphology. Specialized stains like Wright-Giemsa stain can also be used to differentiate eosinophils from other granulocytes in blood smears.

What Role Do Eosinophils Play in Disease?

Eosinophils are implicated in various diseases beyond parasitic infections and allergies. They are involved in chronic inflammation and can contribute to tissue damage in conditions such as eosinophilic esophagitis, where excessive eosinophils accumulate in the esophagus, causing inflammation and damage.

What are the Key Morphological Features of Eosinophils?

Key morphological features of eosinophils include their bilobed nucleus and the presence of large, eosinophilic granules in the cytoplasm. These granules contain major basic protein (MBP), eosinophil peroxidase (EPO), and other enzymes that contribute to their immune function. The granules are membrane-bound and can be visualized using electron microscopy for detailed structural analysis.

Conclusion

Eosinophils are a vital component of the immune system with distinctive morphological features and significant roles in combating parasitic infections and mediating allergic reactions. Their study in histology provides valuable insights into their function and involvement in various diseases, aiding in diagnosis and understanding of immune responses.