Gr1

Gr1, often written Gr-1 or Gr1 in the literature, is a historical designation in mouse immunology for a cell surface antigen detected by the Gr-1 monoclonal antibody RB6-8C5. It is used to identify granulocytic and certain myeloid populations in mice and has been a common tool in studies of inflammation, infection, and cancer.

The Gr-1 antibody RB6-8C5 recognizes members of the Ly6 family, principally Ly6G and Ly6C. Because the antibody binds both Ly6G and Ly6C, Gr-1 staining marks neutrophils (Ly6G+) as well as subsets of monocytes and other Ly6C-expressing cells. In practice, researchers often employ additional, more specific markers (such as the Ly6G-specific antibody 1A8) to distinguish neutrophils from Ly6C+ monocytes within Gr-1+ populations.

Applications of Gr-1 staining include flow cytometry and cell sorting in mouse hematopoietic and immunology research. It is used to monitor myeloid cell responses during infection, sterile inflammation, tumor progression, and immune regulation. A key limitation is that Gr-1 does not label a single, uniform cell type; it encompasses multiple lineages, and its expression can vary by tissue and mouse strain. Additionally, Gr-1 is not a marker for human cells, as the Ly6 family and the RB6-8C5 antibody do not cross-react with human counterparts.

Variants and nomenclature: the term Gr-1 is sometimes written Gr1 or Gr-1, and its usage has declined in favor of Ly6G/Ly6C-based terminology. See also Ly6 gene family, RB6-8C5, and Ly6G/Ly6C antibodies for more precise cell identification.