CD77

CD77, also known as globotriaosylceramide (Gb3), is a glycosphingolipid that resides on the outer leaflet of the cell membrane. It carries a ceramide lipid tail with a carbohydrate head group that includes the Galα1-4Galβ1-4Glc sequence. As a member of the CD antigen family, CD77 is identified by specific monoclonal antibodies used in research and clinical immunophenotyping.

Expression patterns of CD77 vary by cell type. In normal physiology, Gb3/CD77 is expressed on a subset of hematopoietic cells, including germinal center B cells, and is detectable on various other cell types to differing extents. In hematologic malignancies, CD77 is frequently expressed on Burkitt lymphoma cells and can aid in immunophenotypic profiling alongside markers such as CD19, CD20, and CD10. Its presence is not exclusive to a single disease category, so it is interpreted within a broader diagnostic panel.

A key functional aspect of Gb3/CD77 is its role as a receptor for Shiga toxin (verotoxin), produced by Shigella dysenteriae and certain Escherichia coli strains. Binding of Shiga toxin to Gb3 facilitates toxin internalization and contributes to cellular injury, particularly in vascular endothelium, which underpins the pathogenesis of hemolytic uremic syndrome.

Detection and clinical relevance: CD77 is detected by immunohistochemistry or flow cytometry using specific antibodies. In pathology, CD77 expression supports the diagnosis of Burkitt lymphoma in the appropriate immunophenotypic context, but it should be interpreted with other markers and clinical information.