CD68

September 24, 2023

CD68 is a specialized type of protein highly expressed in cells of the monocyte-macrophage lineage. It serves as a marker for these cells in various tissues and is involved in the immune system’s response to pathogens and the clearance of cellular debris.

What does CD68 do?

• Phagocytosis: CD68 is involved in the process of phagocytosis, where macrophages or histiocytes engulf and digest cellular debris, foreign substances, microbes, and cancer cells.
• Immune response regulation: It plays a role in modulating the immune response, including the presentation of antigens to T cells, which is crucial for the adaptive immune response.
• Inflammation: CD68-positive cells are often involved in inflammatory responses, secreting cytokines that mediate and regulate inflammation.

Normal cells that express CD68

• Macrophages: These are the primary cells expressing CD68. Macrophages are found in virtually all tissues, playing key roles in immune surveillance, debris clearance, and inflammation. They are particularly abundant in the spleen, liver (Kupffer cells), lung (alveolar macrophages), brain (microglia), and bone marrow.
• Histiocytes: Histiocytes are a type of macrophage found within tissues throughout the body. They express CD68 and are involved in the immune response, particularly in phagocytizing debris and pathogens. Histiocytes play a crucial role in tissue repair and the inflammatory response.
• Monocytes: In the bloodstream, monocytes express CD68. These cells can migrate into tissues and differentiate into macrophages or dendritic cells, depending on the signals they receive from the environment.

Cancers that express CD68

While CD68 is primarily a marker for macrophages and histiocytes, its expression can be observed in certain cancer types, particularly those originating from or involving macrophages/histiocytes or related cells:

• Histiocytic sarcoma: A rare cancer derived from macrophages or dendritic cells that can express CD68.
• Some forms of lymphoma: Especially those involving macrophage-rich environments or where the cancer cells themselves have characteristics of macrophages.

Detection of CD68 in tissue samples

Common tests used to detect CD68 in a tissue sample include immunohistochemistry (IHC) and flow cytometry. While IHC provides spatial information about where CD68 is expressed within tissue samples, flow cytometry offers quantitative data on the proportion of cells expressing CD68 and the intensity of that expression, making it invaluable for diagnosing and monitoring blood cancers.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

Other helpful resources

Atlas of pathology