Cluster of Differentiation
- CD markers are cell-surface proteins
- Originally defined by monoclonal antibodies
- Used to:
- Identify cell lineage
- Determine cell maturity
- Guide diagnosis, prognosis, and therapy
Example:
- CD20 → mature B cells
- CD3 → T cells
- CD34 → hematopoietic stem cells / blasts
2. Role of CD Markers in Cancer Treatment
A. Diagnostic classification (pathology / flow cytometry)
CD markers help classify cancers:
- Leukemia vs lymphoma
- B-cell vs T-cell
- Acute vs chronic
Example:
B. Therapeutic targets (very important in oncology)
Many modern cancer therapies are CD-directed.
Naked monoclonal antibodies
| Target CD | Drug | Indication |
|---|---|---|
| CD20 | Rituximab | B-cell NHL, CLL |
| CD38 | Daratumumab | Multiple myeloma |
| CD52 | Alemtuzumab | CLL |
| CD30 | Brentuximab* | Hodgkin lymphoma |
*Brentuximab is an ADC, not naked
Antibody–drug conjugates (ADCs)
| Target CD | Drug | Payload |
|---|---|---|
| CD30 | Brentuximab vedotin | MMAE |
| CD33 | Gemtuzumab ozogamicin | Calicheamicin |
| CD79b | Polatuzumab vedotin | MMAE |
Radioimmunoconjugates
| Target CD | Drug | Radioisotope |
|---|---|---|
| CD20 | Ibritumomab tiuxetan | Y-90 |
| CD20 | Tositumomab | I-131 |
Cellular & immune therapies
- CAR-T cells:
- CD19 (tisagenlecleucel, axicabtagene)
- Bispecific antibodies:
- CD20 × CD3 (mosunetuzumab, glofitamab)
3. CD vs Non-CD Targets
Not all cancer drugs are CD-based.
4. Important Clarifications (Common Confusion)
| Term | Meaning |
|---|---|
| CD | Cluster of Differentiation |
| CDK | Cyclin-dependent kinase (e.g., CDK4/6 inhibitors) |
| ADC | Antibody-drug conjugate |
| ICI | Immune checkpoint inhibitor (not CD-based) |
5. Bottom Line (Clinical Takeaway)
- CD = Cluster of Differentiation
- Represents cell-surface antigens
- Central to:
- Hematologic cancer diagnosis
- Targeted monoclonal antibodies
- ADCs, radioimmunotherapy, CAR-T
Synonyms
CD