December 15, 2023

Keratinocytes are specialized cells that make up the majority of cells in the epidermis, the outermost layer of the skin. They are named for their role in producing keratin, a key structural protein that contributes to the skin’s strength and resilience. Under microscopic examination, these cells appear bright pink because the keratin inside the cytoplasm (body) of the cell binds strongly to eosin, a pink dye in the routine H&E stain.

Where do keratinocytes come from?

Keratinocytes arise from basal cells found in the basal or deepest part of the epidermis (the stratum basale). They gradually mature as they move upwards through the layers of the epidermis, undergoing a process called keratinization. During this process, the cells change in shape, lose their nucleus (the part of the cell that holds the genetic material) and other cellular organelles, and fill up with keratin. Once keratinocytes reach the outermost layer of the epidermis (the stratum corneum), they are filled with keratin. Eventually, these cells are removed from the epidermis in a process called desquamation, and new keratinocytes from the deeper layers replace them.

What do keratinocytes do?

The primary function of keratinocytes is to form a protective barrier. This barrier protects against environmental damage such as pathogens, UV radiation, and physical abrasions. These cells also play a crucial role in regulating water loss from the body, thus helping in maintaining proper hydration levels. When the skin is injured, keratinocytes are activated and play a key role in wound healing. They can produce signaling molecules that help in the immune response and in the repair of damaged tissue. Keratinocytes also interact with other cell types in the skin, such as melanocytes (which produce pigment) and Langerhans cells (which are involved in the immune response).

Immunohistochemical markers

The following are markers commonly expressed by keratinocytes. Pathologists use a test called immunohistochemistry (IHC) to identify cells expressing these markers.

About this article

Doctors wrote this article to assist you in reading and comprehending your pathology report. Feel free to reach out to us with any questions about this article or your pathology report. To get a comprehensive introduction to your pathology report, read this article.

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