Written and maintained by CASRAI Editorial Board
Last updated
General reference for researchers and lab staff. It describes a laboratory marker and is not medical or diagnostic advice.
Short answer
CD68 is a 110-kDa transmembrane glycoprotein located in lysosome and endosome membranes according to UniProt (long isoform). It is used as a macrophage and monocyte marker, but it is enriched in macrophages rather than exclusive to them. CD163 is a different marker: a receptor at the cell surface that is described as expressed in monocytes and macrophages. Using both together is more informative than either alone.
Definition and scope
CD68 (also called GP110, LAMP4 and SCARD1) belongs to the lysosome-associated membrane protein (LAMP) family and is also listed as a scavenger receptor family member. The Human Protein Atlas (read 2026-11-07) reports selective cytoplasmic expression in macrophages, and UniProt notes it could play a role in the phagocytic activities of tissue macrophages. “CD68 marker” in a methods section therefore refers to detecting this protein, usually with an antibody, as a readout for macrophage-lineage cells.
What cells have CD68?
At the single-cell level the Human Protein Atlas lists CD68 as enhanced in Kupffer cells (the highest), Hofbauer cells, microglia, macrophages, monocytes, conventional dendritic cells and platelets. Within monocytes it is enhanced in the classical, intermediate and non-classical subsets. For the differentiation steps that lead from monocyte to macrophage, see monocyte to macrophage differentiation.
CD68 marker and microglia
Microglia are among the cell types in which the Human Protein Atlas reports enhanced CD68 expression, so CD68 is a commonly reported readout for brain-resident macrophage-lineage cells. As with other tissues, a positive signal should be read together with a second marker and with the controls described below.
What does CD68 positive mean?
CD68 positive means the antibody-detectable protein is present in the cells or tissue examined. It indicates a macrophage-lineage identity as a working assumption, not proof. Published work shows why: Beranek (2005, Annals of the Rheumatic Diseases, PMID 15647451), titled “CD68 is not a macrophage-specific antigen”, detected CD68 by flow cytometry on THP-1 cells and on synovial fibroblasts. Gottfried and colleagues (2008, Scandinavian Journal of Immunology, PMID 18405323) are titled “Expression of CD68 in non-myeloid cell types”, which reports CD68 outside the myeloid lineage. Taken together, this literature supports describing CD68 as a lysosomal protein enriched in macrophages rather than a macrophage-exclusive antigen; reported results also depend on the antibody clone and fixation used.
What is the difference between CD68 and CD163?
CD68 is a lysosomal and vesicular protein; CD163 sits at the plasma membrane. They also differ in what they are described as doing and in how tightly they are tied to the monocyte-macrophage lineage. The table below is drawn from the Human Protein Atlas entries read on 2026-11-07 and the UniProt CD68 entry (P34810), plus the two papers cited above for the CD68 specificity row.
| Feature | CD68 | CD163 |
|---|---|---|
| Other names | GP110, LAMP4, SCARD1 | M130, MM130, SCARI1 |
| Main location | Lysosome and endosome membranes (UniProt, long isoform); the Human Protein Atlas lists Golgi apparatus and vesicles | Plasma membrane (cytoplasmic staining reported in Hofbauer, Kupffer and alveolar macrophages) |
| Described function | LAMP family member and scavenger receptor family member; could play a role in phagocytosis by tissue macrophages | Acute phase-regulated receptor that binds hemoglobin/haptoglobin complexes and mediates endocytosis; may contribute to iron recycling |
| Cell-type pattern | Enhanced in Kupffer cells, Hofbauer cells, microglia, macrophages, monocytes, conventional dendritic cells, platelets | Described by Entrez as exclusively expressed in monocytes and macrophages |
| Reported outside the myeloid lineage | Yes (THP-1 cells, synovial fibroblasts; primary fibroblasts and endothelial cells stained comparably to macrophages in Gottfried et al. 2008 (abstract)) | No non-myeloid expression is described in the Human Protein Atlas or Entrez entries |
What is CD163 a marker for?
CD163 is used as a marker of monocytes and macrophages. The Human Protein Atlas describes it as an acute phase-regulated receptor on macrophages that binds hemoglobin/haptoglobin complexes and mediates their endocytosis, and Entrez describes it as exclusively expressed in monocytes and macrophages. For how macrophage subtype labels are used and why they are changing, see M1 vs M2 macrophages.
What are the common markers for macrophages?
CD68 and CD163 are the two markers covered by the sources read for this page. The comparison above suggests a practical approach (editorial interpretation, not a standard): pair a broadly expressed lysosomal marker (CD68) with a marker that is more tightly tied to the monocyte-macrophage lineage and sits at the cell surface (CD163), and to state in the methods which clone, fixation and assay were used.
Where it matters for labs
For flow cytometry or staining work, the antibody and the controls matter as much as the marker. The following existing CASRAI guides cover the surrounding bench practice:
- antibody titration for flow cytometry
- FMO, isotype and unstained controls
- PBMC preparation and staining
CD68 checklist
- Record the antibody clone and the fixation method, because reported CD68 results depend on both.
- Do not call a population “macrophages” on CD68 alone; add a second marker such as CD163.
- Remember that CD68 is largely intracellular (lysosome and endosome membranes per UniProt), whereas CD163 is at the plasma membrane.
- Where non-myeloid cells such as fibroblasts could be present, treat a CD68 signal as a possible non-macrophage source.
Common misunderstandings
- “CD68 is macrophage-specific.” It is enriched in macrophages but has been detected on other cells, including THP-1 cells and synovial fibroblasts.
- “CD68 and CD163 are interchangeable.” They have different locations and described functions, as the table shows.
- “CD68 is a surface marker.” UniProt places the long isoform in lysosome and endosome membranes, while the Human Protein Atlas lists Golgi apparatus and vesicles as its main location.
FAQ
What cells have CD68?
Kupffer cells (highest), Hofbauer cells, microglia, macrophages, monocytes, conventional dendritic cells and platelets, per the Human Protein Atlas single-cell data.
What are the common markers for macrophages?
CD68 and CD163 are the two covered here; pair them rather than relying on one.
What is the difference between CD68 and CD163 markers?
CD68 is lysosomal/vesicular and enriched in, but not exclusive to, macrophages; CD163 is a plasma-membrane hemoglobin/haptoglobin receptor described as exclusive to monocytes and macrophages.
What is CD163 a marker for?
Monocytes and macrophages.
Sources
- Human Protein Atlas, CD68: proteinatlas.org/ENSG00000129226-CD68 (read 2026-11-07)
- Human Protein Atlas, CD163: proteinatlas.org/ENSG00000177575-CD163 (read 2026-11-07)
- Beranek JT. CD68 is not a macrophage-specific antigen. Ann Rheum Dis 2005; PMID 15647451: PMC1755344 (read 2026-11-07)
- Gottfried E et al. Expression of CD68 in non-myeloid cell types. Scand J Immunol 2008; PMID 18405323
